Inulin: A Comprehensive Scientific ReviewBryan C. Tungland, 2000
|This detailed review of Inulin, a bifidogenic prebiotic, includes how it affects probiotic function and its role in health and disease|
| A. Origin and History|
| B. Consumption Intakes|
| C. Production|
| A. Probiotics and prebiotics|
| B. Products of fermentation|
| A. Dietary fiber effects|
| B. Caloric value|
| C. Lipids effects|
| D. Minerals effects|
| E. Vitamin effects|
| A. Cancer|
| B. Diabetes mellitus|
| C. Heart disease|
| D. Immune system|
| E. Gastrointestinal Health|
| F. Dental Health|
| G. Skeletal Health and Menopausal Support|
| H. Opportunistic infections (Urinary tract health and Candidiaisis)|
|VI.||Functional Characteristics and Food Applications|
|VII.||Safety and Tolerance|
| A. Legal and Regulatory Status|
| B. Nutritional labeling|
A growing awareness of the complex interactions between diet, the intestinal microflora
resident in the gastrointestinal tract and health has encouraged the development of dietary
strategies promoting the growth of specific bacterial groups perceived to be beneficial. Even
though these complex relationships are now recognized from clinical studies, they remain poorly
understood. Of particular interest is the use of a new class of dietary foodstuffs termed nondigestible
oligosaccharides (NDO). Due to their unique chemical structure some of these
carbohydrates resist digestion by the human alimentary tract. Consequently, they reach the
caeco-colon essentially as intact molecules, not providing the body with digestible
monosaccharides. Because these carbohydrates enter the colon as intact compounds they elicit
systemic physiological functions and act as fermentable substrates for colonic microflora-influencing
the species composition and metabolic characteristics of the intestinal microflora,
and therefore provide important health attributes. Inulin is a natural NDO extracted in industrial
quantities from chicory with potential use in producing physiological functional foods and
promoting human health.
Evidence of the growing interest in inulin is the increased research in both short-chained
fructooligosaccharides (FOS) and the longer chained inulin. A number of review papers have
been published discussing various aspects of the health benefits of FOS and inulin. These
include: Farnworth, 1993; Fuchs, 1992; Gibson and Roberfroid, 1995; Gibson et al., 1996;
Roberfroid, 1993; Roberfroid, 1996; Roberfroid, et al., 1998; Van Loo et al., 1995; and Yuri,
Inulin falls under the general class of carbohydrates called fructans, those polymers
containing fructose. Fructans serve as storage polymers in many members of the CompositX
such as Cichorium intybus (chicory), Inula helenium (elecampane), Taraxacum officinalis
(dandelion), and Helianthus tuberosus (Jerusalem artichoke). Inulin extracted from chicory is a
natural polydisperse carbohydrate (Phelps, 1965). It is known as a fructan consisting
predominately of linear chains of 1,2-B-linked d-fructofuranose units bound by a (a1-B2) type
linkage (as in sucrose) to a terminal glucose moiety. All fructans found in the dicotyledons, as
well as some monocotyledons, are of this type. By comparison, fructans composed
predominately of linear fructose units bound by a B(2-->6) glycosidic bond are typically levans
that are produced by many soil and oral bacteria, yeasts and fungi.
The gross molecular formula of inulin is GFn, with G being a terminal glucosyl unit, F
representing the fructosyl units and "n" representing the number of fructosyl umits. The basic GF2
trimer in inulin and the shortest fructan of the inulin type is 1-kestose. The same bonds link the
ensuing fructosyl units, i.e. P(2-->l) as that in 1-kestose, Figure 1.
Figure 1: Chemical Structure of sucrose (left), inulin (center), oligofructose (right)
Short chain fractions of fructooligosaccharides such as 1-kestose, the major GF,
compound in chicory roots or Jerusalem artichoke, and neokestose in onion do not differ
analytically (Van Loo et al., 1995). Further, fructan chains linked to either of these naturally occurring
trisaccharides have the B(2-->1) configuration, implying that with the exception of one
glycosidic linkage within the basic trisaccharide there is no difference between a fructan
molecule based on 1-kestose or neokestose. The chain length or degree of polymerization (DP)
in such molecules is n+ 1.
Pollock et al., (1993) reviewed the enzymology of fructan synthesis in vivo. The natural
biosynthesis of inulin within plant cells begins by the cells using a vacuolar enzyme, sucrosesucrose
fructosyltransferase (SST), to catalyze the reaction (Equation 1) that produces
trisaccharides (Isokestose, kestose, and neokestose) and a glucose molecule from two sucrose
molecules (Edelman & Dickerson, 1966).
Equation 1. GF + GF --> GFF + G
Sucrose-sucrose fructosyltransferase is only active at high concentrations of sucrose (6-15%)
so fructan metabolism is an extension of the sucrose metabolism. Following trisaccharide
production, the polymeric chain is lengthened by the action of another vacuolar enzyme, fructan-fructan
fructosyl transferase (FFT), catalyzing the transfer of a unit of fructose from one donor
polymer to another acceptor. The enzyme uses the trisaccharide formed by SST for further chain
elongation of the fructan polymer, releasing sucrose (Equation 2). Therefore, SST and FFT have
some overlapping activities. During this transfer sucrose molecules only act as acceptors and
cannot function as donors. The balance mechanism between the various fructans with a different
DP and in the absence of new syntheses appears to have a regulatory effect on the plant's
physiology (Marchetti, 1993a).
Equation 2. G(F)n + G(F)m --> G(F)n-1 + G(F)m+1
Inulin from chicory is a mixture of oligomers and polymers of fructose having varying
degrees of polymerization (DP), but typically having a DP range from three (corresponding to
GF2) to about 60 with a modal chain length of approximately nine. Native inulin from
chicory often is made up of about 1 - 2 percent B(2-->6) branching with short side-chains (Van
Loo et al., 1995). In addition to having predominately linear chains of the GFn-type, native
inulin extracted from fresh chicory roots also has been shown to contain about 1-1.5% (Fn)
compounds on dry solids, those composed of homopolymers of fructose bound by a B(2-->1)
linkage (Van Loo et al., 1995). The rn represents the number of fructosyl moieties in the
homopolymers. Both GFn and Fm have very similar physicochernical properties except that Fm type
products are reducing, due to the presence of a reducing fructose-end group, whereas GFn
compounds are not.
An understanding of different terms used to describe fructose-containing polymers is
important as more commercial products become available. Oligofructose was introduced as a
synonym for fructo-oligosaccharides in 1989 (Coussement, 1999). The oligofructose product is
a partial enzymatic hydrozlyate of native chicory inulin containing predominately molecules of
the Fm-type (homopolymers of fructose bound by a B(2-->1) glycosidic linkage having no terminal
glucose), Figure 1. Oligofructose has been defined by the IUB-IUPAC Joint Commission on
Biochemical Nomenclature and the AOAC as fructose oligosaccharides containing 2-10
monosaccharide residues connected by glycosidic linkages (Niness, 1999). As previously stated,
inulin, as extracted from chicory root, is a polydisperse fructan with chain lengths ranging from
2 to 60 units with a modal DP of ± 9. Commercial chicory inulin is composed of approximately
2% monosaccharides, 5% disaccharides and 93% inulin. Neosugar is a FOS mixture of kestose
(n=2), nystose (n=3) and IF-B-fructofuranosyl nystose (n=4). Basically these are sucrose
molecules to which one to three additional fructose units have been added. The development
and isolation of neosugar was first reported in the Japanese literature in 1983 (Oku et al., 1984).
Neosugar can be isolated from brans of triticale, wheat and rye or artificially by the action of the
fungal enzyme 0-fructofuranisidase on sucrose, the enzyme being a product of the fungus
Aspergillus niger (Fishbein et al., 1988). Using the most widely available and accepted
nomenclature, all FOS and inulins are fructans, all FOS are inulins, but not all inulins are FOS.
Those inulin molecules having a degree of polymerization of < 10 fructose units generally are
considered to represent FOS.
II. (a). Origin and historical human consumption. Inulin was discovered by Rose, a German
scientist, who in 1804 found "a peculiar substance" from plant origin in a boiling water extract
from the roots of Inula helenium, a genus of perennial herbs of the group Compositae, natives of
the temperate regions of Europe, Asia, and Africa (Goudberg, 1913). The substance was named
inulin but was also identified by other names such as helenin, alantin, meniantin, dahlin,
sinanternin, and sinisterin. The biochemical production was elucidated around the middle of the
Inulin belongs to the group of naturally-occurring carbohydrates known as non-digestible
oligosaccharides (NDO). It is produced naturally in over 36,000 plants worldwide, including
1,200 native grasses belonging to 10 families. After starch, they are the most plentiful
carbohydrates occurring in the plant kingdom (Carpita et al., 1989; Marchetti, 1993b). It has
been estimated that as much as one third of the total vegetation on earth consists of plants that
contain fructans. Inulin-type carbohydrates obtained from fungal fermentation have been
reported in commercial use but the predominant commercial source for Inulin/FOS is of chicory
root origin. Inulin has extensive documented historical human use through the consumption of
edible plants and fruits - a variety of which are common foodstuffs (Table 1).
Table 1: Inulin content of foods consumed by Americans
Inulin is an energy-reserve carbohydrate and may act as an osmoprotectant in plants.
Because inulin is readily soluble in water, it is osmotically active. By changing the DP of the
molecule in the plant's vacuole, the plant can readily change the osmotic potential of its cells
without altering the total amount of carbohydrate. The internal hydrolysis of inulin by
endoinulinase to lower DP Fm, and GFn molecules allows plants to osmoregulate, surviving
winter periods in cold to moderately cold and drought stricken regions (Edelman & Jefford,
Historically, several inulin-laden foods, especially chicory, dahlia, Jerusalem artichokes,
munong, and yacon, have been used as staple food or as sustenance crops. Australian
aborigines ate murnong, a tuberous plant, in the 19th century as their main vegetable food with a
reported daily intake of 200-300 grams (Gott, 1984).
Chicory is indigenous to Europe and has been cultivated since the 16th century with the
roots and greens (known as Belgian endive) being used for human consumption. Post-World
War 11 populations in England and Germany roasted root of the chicory plant to use as an
extender or substitute for coffee beans (Meijer et al., 1993). This concept is still in use in the
southern United States, particularly Louisiana. A cup of chicory coffee may contain three grams
inulin (Douglas & Poll, 1986; Van Loo et al., 1995).
In the South Pacific a variety of yacon was introduced to Japan from New Zealand and
grew in popularity (Asami et al., 1989). Native Americans used the Jerusalem artichoke tuber,
native to North America, for food. Jerusalem artichokes were found by Champlain at Cape Cod,
Massachusetts and were introduced in France in 1605, becoming the main source of
carbohydrate in Western Europe until it was superseded by the potato in the middle of the 18th
century (Wyse & Wilfahrt, 1982). Jerusalem artichokes were again cultivated as a staple crop by
the post-World War II French and Germans due to scarcity of the potato at the time.
II (b). Common Intakes in Diet. Historically, daily inulin intake was estimated to be
approximately 25 to 32 grams. Today, the average daily intake of inulin and its hydrolysis
products in Western Europe is estimated between 2-12 g/person/day (Roberfroid, Gibson, &
Delzenne, 1993). The U.S. consumption, estimated at 2-8 g/person/day, is slightly less based on
data from the U.S. Nationwide Food Consumption Survey 1987-88 (Roberfroid et al., 1993).
A more recent USDA study by Moshfegh et al., (1999) showed that American diets
provide about 2.6 g of inulin and 2.5 g of oligofructose. Mean intakes varied by gender and age
groups with a range from 1.3 grams for young children to 3.5 grams for teenage boys and adult
males. Per 1000 calories, mean intake ranged from 0.9 to 1.5 grams in American diets.
Significant differences exist between variable sociodemographic categories. Whites who make
up 73% of the US population consume significantly more of these inulin-containing components
than Blacks or Hispanics (Moshfegh et al., 1999). The primary sources of inulin in American
diets are wheat and onions, Figure 2.
Figure 2: Primary vegetable sources of inulin in the American Diet
II. (c). Production. Until recently, inulin as a pure compound was not produced economically
on an industrial scale and was not available as a food ingredient for human consumption. Inulin
was produced on a pilot scale in Deutsche Kulorfabrik in the early 1920s (Schone 1920), and
later was extracted on an industrial scale. In 1927 Belval reported several German sugar factories
extracted inulin from chicory, similar to sugar extraction from sugar beets. Like sugar from sugar
beets, the extract was high in impurities that were removed by lime-carbon dioxide purification.
Chilling precipitation further purified the inulin. However, the production process was deemed
uneconomical due to the recovery process using precipitation by chilling (Gibson et al., 1994).
Today's process is significantly more efficient and economical.
The primary industrial source of pure inulin is the chicory root (Cichorium intybus L.).
Chicory is a member of the Compositx family. Other significant inulin-containing members of
this family are dandelion, lettuce, globe and Jerusalem artichoke, dahlia and yacon. Other
inulin-containing plants belong to the Liliales family, e.g. leeks, onion, garlic and asparagus.
Although chicory has been cultivated for centuries, it still remains quite wild, having only had
very minor influence in its genetic basis since its early cultivation occurred in England in 1548.
The ancestral form of chicory is a perennial plant (var. silvestre) that probably originated in East
India and grew widespread in the Mediterranean areas of Europe and Near Asia. Cultivated root
chicory is a biennial plant that is grown as a long season annual. The root is indigenous to
Western Europe and was cultivated on a larger scale beginning in the 16th century before being
exported to the United States in 1806. Chicory is now a common purplish-blue-flowering weed
growing wild in roadway ditches in the United States and Canada.
A distinction is made in cultivation between the three basic forms of chicory. The slightly
bitter, curled dandelion-like greens (called Italian dandelion) are grown and used as potherbs.
Witloof chicory, Cichorium endivia Linn Endive (also called French endive or Belgian endive) is
a perennial herb that is forced as a blanched vegetable and used as a salad delicacy. Root chicory
varieties, Cichorium intybus Linn var. sativum, have been used as roasted roots in Europe and
North America to impart additional color, body and sedative action as a coffee extender or
coffee substitute. In the last ten years, European root chicory cultivation has provided a means to
produce high purity fructose syrups and refined inulin products with various chain lengths.
Chicory root is a biennial plant requiring soil and climatic conditions resembling those
for sugar beets: deep, fertile, permeable and cool soil with pH tending towards neutral;
intolerance of droughts or poor drainage. The best conditions for high yields are mild maritimelike
climates, rich light -clay to sandy- soils and long periods of daily illumination, similar to
that in Western European countries like France, Holland and Belgium. The plant, being similar
to the sugar beet root, shares similarities in agronomic practices and inulin production
technologies. The inulin production process involves three general steps: extraction of raw inulin with hot water, purification of the raw inulin and spray drying of the purified juice to a pure inulin powder. Although inulin is spray dried, the molecule is quite flexible, and crystallizes easily (French, 1989). Further outline of the process is given in Figure 3.
Figure 3: Inulin production process
III. BIFIDOGENIC PROPERTIES
The large intestine is the most heavily colonized region of the digestive tract, with up to 1011 bacteria for every gram of intestinal content (Gibson & Roberfroid, 1995). Gut bacteria are comprised of one hundred different species that include both beneficial and potentially deleterious bacteria in a balance that affects how food is digested and energy is obtained, Figure 4, When the main types of generally recognized beneficial bacteria, bifidobacteria and lactobacilli, are at optimum levels they constitute approximately one-third of the bacterial population in the gastrointestinal tract. In some cases the numbers of beneficial bacteria may be so low they are undetectable. The numbers of bifidobacteria are regarded as a marker of the stability of the human intestinal microflora (Mutt & Tanaka, 1987).
Figure 4: Schematic overview of colonic microflora and their health significnce
The importance of an indigenous microflora population as a natural means to fight potential pathogenic microorganisms was recognized by Metchnikoff during research on cholera in the 19th century (Bibel, 1988). Decades later, the importance of a well-balanced gut microbial ecosystem is becoming more widely recognized for host health. Research by Mutai and Tanaka (1987) stimulated further efforts to identify the role of bifidobacteria (Mitsuoka, 1990a; Romond & Romond, 1987), and other lactic acid bacteria, mainly lactobacilli (Salminen et al., 1993a, 1993b; Tannock, 1990) with regard to host health. Miller-Catchpole (1996) noted that bifidobacteria, even though implicated in incidental opportunistic anaerobic infections (as in individuals with weakened immune systems), are generally regarded as safe. Stimulation of bifidobacteria numbers as well as the numbers of lactobacilli in the colon is beneficial to host health.
Populations of bifidobacteria can represent up to 95% of the total intestinal microflora in breast-fed infants, in comparison with about 25% in the adult (Gibson, 1995). The mothers delivery canal and fecal flora inoculate the gastrointestinal tract of the newborn during birth (Gibson & Roberfroid, 1995). Drasar and Roberts (1989) recognized that fecal flora of breast-fed infants is dominated by populations of bifidobacteria, with only one percent enterobacteria. By contrast, formula-fed infants have a more complex microflora, with bifidobacteria, bacteroides, clostridia and streptococci all prevalent (Gibson & Roberfroid 1995). Although bifidobacteria have been considered to be the most important organisms in infants, and lactobacilli and E. coli are more numerous bacteria for children and adults than bifidobacteria it has now become clear that bifidobacteria also constitute one of the major organisms in the colonic flora of healthy children and adults (Mitsuoka, 1990b). The fecal material of children and adults have bacteroidaceae, eubacteria and peptococcaceae that outnumber bifidobacteria, which constitute 5 to 10% of the total flora. The numbers of enterobacteriaceae and streptococci in children and adults are also less than bacteroides, eubacteria, peptocococceae and bifdobacteria decreasing to less than 108 CFU per gram of fecal material. lactobacilli and veillonellae are also present in children and adult fecal material, but in numbers that usually are less than 108 CFU per gram (Mitsuoka, 1990b). In elderly persons bilidobaderia decrease or completely disappear, putrefactive bacteria like clostridia including C. perfringens, significantly increase. In addition, lactobacilli, streptococci, and enterobacteriaceae also increase, Figure 5.
Figure 5, Changes in the fecal Flora with increased age (from Mitsuoka, 1990b).
Thus, it is thought that presence of these healthy microorganisms in breast-fed infants contributes to their alleged health advantages compared to formula-fed infants, and the modification of elderly and maintenance of weaned bifidobacteria microflora patterns may provide a means to maintain health and potentially prevent some gut-home diseases. Following weaning, the microflora pattern in breast-fed infants begins to resemble that of adults.
As a consequence to findings by Mutai and Taankk (1987); Romond and Romond (1987); Drasar and Roberts (1989); and Mitsuoka (1990a) and a number of other researchers, scientists now generally ascribe to the beneficial health effects of bifidobacteria in the colon, Figure 6.
Figure 6: colonic bacteria and SCHFA related health effects of bifidobacteria
Predominant gut microflora generally recognized as producing health promoting inactions, are the Bacteroides, Bifidobacterium, lactobacilli, and Eubacterium (Gibson &.
Roberfroid, 1995). These beneficial microflora particularly the bifidobacteria and lactobacilli, may play critical roles in all aspects of our immunological responses, by either helping to resist infection, or by creating conditions which reduce the number of pathogenic bacteria. These beneficial bacteria may act as wards regulating the activity of the other bacteria in the colon. The other bacteria, such as Salmonella, Shigella, Clostridia, Staphylococcus aureaus, Candida albicans, Campylobacter jejuni, Escherichia coli, Veillonella, and Klebsiella, have varying potential to cause disease and are much less numerous. However, these pathogenic bacteria and several strains of yeasts, most notably Candida albicans, can produce harmful local and systemic effects if they overgrow as a consequence of a gut microflora imbalance (Elmer et a1., 1996).
Research has shown beneficial bacteria, particularly bifidobacteria and lactobacilli, keep these potential disease-causing organisms under control, preventing several disease-related dysfunctions related to an imbalances GI situation (Elmer et a1., 1996).
Bifidobacteria, while significantly influencing other colonic microflora, are also affected
by many exogenous and endogenous factors. Factors affecting intestinal flora observed by Rasic (1983) were: animal species; habits; age; sex; climate; diet; stress; exogenous organisms; and
immune mechanisms of the host. Other modifers of the gut microflora are surgery of the
stomach or small intestine, kidney or liver disease, cancer, pernicious anemia, blind loop
syndrome or a change in the acidity of gastric juices (Modler et al., 1990). In addition, other
pathogenic disorders, such as liver cirrhosis and impaired intestinal motility may modify colonic microflora. During stages of acute infection, antibiotic therapy used to combat the bacterial
invasion can also induce digestive disorders due to alteration of normal gut flora. Bifidobacteria have been shown to be resistant to streptomycin, but have only moderate resistance to penicillin,
tetracycline, neomycin and novobiocin (Kurmann and Rasic, 1991). Bifidobacteria can be
completely eradicated from the colon when antibiotics such as erythromycin, spiramycin and chloramphenicol are used to combat other bacterial infections.
Reducing or eliminating more of the healthy gut microflora, like bifidobacteria, has its
consequences. When the human diet influences the species composition and metabolic
characteristics of the intestinal microflora, toxic metabolite production is affected, such as the
conversion of procarcinogens to active carcinogens (Perman, 1989; Roland et al., 1993;
Rowland, 1988). E. coli and clostridia are known to produce ammonia and amines, both liver
toxins, and carcinogens and cancer promoters such as nitrosamines, phenols, cresols, indole and skatole, estrogens, secondary bile acids and aglycones. Chadwick and coworkers (1992) reported
reductive enzyme activities are lower in bifidobacteria and lactobacilli relative to E. coli and
clostridia. Bacteroides are generally thought to be health promoting, while Enterococcus faecalis produce nitrosamines, aglycones and secondary bile acids, and Proteus produces
ammonia, amines and indole (Drasar & Hill, 1974; Kanbe, 1988; Koizumi et al., 1980;
Mitsuoka, 1982, 1990a). In addition to producing toxic metabolites, several harmful bacteria,
such as Salmonella, Shigella, Listeria, Bacteroides, Proteus, E. coli, Clostridium perfringens and Vibrio cholerae also have association with diarrhea, infections, liver damage, carcinogenesis and intestinal putrefaction. It is possible the health promoting effects prompted by bifidobacteria and other healthful bacteria is due to the growth inhibition of harmful bacteria, stimulation of
immune functions, lowering of gas distention problems, improved digestion/absorption of
essential nutrients and synthesis of vitamins (Gibson, 1995; Gibson & Roberfroid, 1995; Roberfroid & Delzenne, 1993).
Pathogenic effects associated with harmful intestinal microflora such as E. coli,
Clostridia, Bacteroides, Proteus, Salmonella, Shigella, and Vibrio cholerae not only include
colonic disorders but also have implication with possible vaginal infections and systemic
disorders. Intestinal pathologies include antibiotic-associated diarrhea (AAD), inflammatory
bowel diseases (IBD) such as ulcerative colitis and Crohn's disease, colorectal cancer,
necrotizing entercolitis, and ileocecitis. Vaginal infections include candidal vaginitis while
systemic disorders include gut origin septicemia, pancreatitis and multiple organ failure
syndrome (Gibson & Roberfroid, 1995), Figure 7. Major factors in the biology of these
disorders are the overgrowth of pathogenic bacteria such as clostridia, E. coli, as well as
parasites, viral infections, extensive bum injury, post-operative stress, and antibiotic therapy.
These disorders are often associated with bacterial translocation due to intestinal barrier failure
(Gardiner et al., 1993; Gibson & MacFarlane, 1994; Solomons, 1993).
Figure 7: Pathogenic microflora suppression, from Roberfroid et al. 1998 and Rolfe 1981
Mechanisms related to microflora modification to a more-healthy environment vary for
individual microflora groups. However, the antagonistic effects of lactic acid bacteria have been
attributed to favorable competition for active sites on the colonic epithelial wall, the production
of primary metabolites, such as acetic, lactic, propionic, butyric and benzoic acids, and hydrogen
peroxide and the secretion of specific bacteriocins, e.g. Lactacins B,F and Lactocin 27 (Gibson
and Wang, 1994c; Modler et al., 1990). Numerous other investigators have also reported the
ability of lactic acid bacteria to produce antibacterial substances, which are active against certain
pathogenic and putrefactive organisms (Mehta et al., 1983). Some Streptococcus spp. have also
been shown to produce bactericidal substances (Miller-Catchpole, 1989). L. acidophilus strains
produce three antibiotic substances, namely acidolin, acidophilin and lactocidin; L. bulgaricus produces one antibiotic substance, bulgarican.
Although bifidobacteria do not produce hydrogen peroxide, observations by Gibson and Roberfroid (1995) hint that bifidobacteria might secrete a bacteriocin-type substance that is
active against Clostridia, E, coli, and many other pathogenic bacteria, such as Listeria, Shigella,
Salmonella, and Vibrio cholerae, or antimicrobal substances. Anand and coworkers (1985)
tested six strains of B. bifidum for their antibacterial activity and reported that antibacterial
activity differed among the strains with maximum inhibitory action shown by one strain against M. flavus followed by Staph. aureus, B. cereus, E. coli, Ps. flourescens, S. typhosa and Sh. dysenteriae.
Like lactobacilli, bifidobacteria produce strong acids, i.e. acetic and lactic acid (Scardovi,
1986). The production of these acids reduces intestinal pH. One effect of lowering the
gastrointestinal pH might be the protonation of toxic ammomia (NH3) to produce ammonium ion
(NH4+), which is non-diffusable and could result in lower blood ammonia levels and a reduced
hepatic load (Levrat et al., 1993; Miller-Catchpole, 1989). An additional, and potentially more
important effect is restriction or prohibition of the growth of many potential pathogens and
Acetic acid has been observed to exert a greater antimicrobial effect than lactic acid,
most likely due to a greater amount of undissociated acid at intestinal pH values (5.8) common
to bifidobacteria and lactobacilli (Modler et al., 1990). Because bifidobacteria produce almost
two-fold more acetate than lactate, the undissociated acetic acid would be approximately 11 -fold
greater than lactate. This is an important factor as the growth of many potential pathogenic
bacteria is very sensitive to concentrations of undissociated acid (Modler et al., 1990).
Scardovi (1986) suggested the optimum pH for bifidobacteria is between 6.5 and 7.0 with
little or no growth below the pH range of 4.5 to 5. 0 or above 8. 0 to 8.5. Wang and Gibson (1993)
observed that specific growth rates of B. infantis, E. coli and Cl. perfringens were
approximately equal at neutral pH. As the pH was lowered the bifidobacteria growth rate
remained relatively unaffected while the growth of E. coli and Cl. Perfringens was completely
inhibited at pH 5.0 and 4.5.
Bifidobacteria do not form aliphatic amines, hydrogen sulfide or nitrites (Bezkorovainy & Miller-Catchpole 1989). They produce vitamins, largely of the B-group, such as biotin,
thiamine, riboflavin, niacin, pyridoxine, cyanocobalamin, and folic acid (Deguchi et al., 1985;
Gibson et al., 1995; Hartemink et al., 1994). These bacteria also produce digestive enzymes
such as lactase (B-galactosidase), casein phosphatase and lysozyme that may improve lactose
tolerance and digestibility of dairy products (Hughes & Hoover, 1991).
III. (a). Probiotics and Prebiotics To minimize the potential for imbalances in gut microflora which could lead to intestinal, systemic and, possibly, vaginal infections, researchers have
investigated various means of achieving a greater population of healthy gut microflora. There is
growing evidence that live selected bacteria, such as bifidobacteria and lactobacilli, when added
to food (such as fermented milk beverages or yogurt) or used as a dietary aid, are beneficial for
these purposes. Probiotics are defined as living microbial feed supplements added to the diet,
which have beneficial effects on the host by improving its intestinal microflora balance (Fuller,
1989). In humans, lactobacilli, either as single species or in mixed culture with other bacteria
such as bifidobacteria and streptococci, are common probiotics (Gibson, 1995).
When probiotics are added to the diet as a large bowel target to bring about microflora balance, these organisms must reach their intended destination intact and become viable. There
is evidence that some probiotics added in the diet are able to reach the colon and provide health
benefits (Elmer et al., 1996; Kageyama et al., 1984; Pochart et al., 1992). However, due to
fluctuating activities in response to substrate availability, redox potential, pH, oxygen tension
and colonic distribution, the survivability and effectiveness of ingesting living microorganisms
for purposes of targeting colon microflora modulation is variable.
In addition, incorporation of healthy viable bacteria into processed foods is also
somewhat difficult because of their high susceptibility to oxygen, shear, heat, and pH sensitivity
(Tomomatsu, 1994). Intake of food as a bolus and the development of species that are more
oxygen and acid-resistant is probably of importance. Further, due to competition for nutrient
sources and colonization sites with previously well established endogenous microflora,
individual probiotic fixation and activities are strain-dependent. There is also evidence that probiotic effects are transient. When consumption of the probiotic product ceases, the added
bacteria are excreted (Bouhnik et al., 1992). However, in order for bifidobacteria to benefit host
health, it is necessary that these organisms be metabolically active in the lower gastrointestinal
tract (Hashimoto, 1985; Tamura, 1983).
As a prerequisite to their survivability, these bacteria require a carbohydrate source to use
for fermentation that has not been metabolized by the human digestive system before reaching
the colon. Selective non-digestible carbohydrate food sources that promote the proliferation of bifidobacteria and lactobacilli have been defined as prebiotics (Gibson and Roberfroid, 1995). Prebiotics that would have potential use, as ingredients in foods should be non-digestible, very
shelf stable, require no refrigeration, be easily and effectively incorporated into processed foods
and nourish all endogenous beneficial bacteria. The combined form of a probiotic and prebiotic, as described by Gibson and Roberfroid (1995) is termed a synbiotic. In a review,
Fuller and Gibson (1997) discuss a variety of mechanisms that may be responsible for the
beneficial effects of pro- and prebiotic supplements. A comparison of the terms probiotic, prebiotic and synbiotic is presented in Table 2 (Gibson and McCartney, 1998).
Table 2: Gut microflora definitions & mechanisms of gut modulation, Gibson & McCartney 1998
Various in vitro and in vivo studies have shown that a diet supplemented with B(2-1) inulin/FOS provides an effective means to promote growth of bifidobacteria and lactobacilli,
while selectively reducing the growth of pathogenic microorganisms and potentially treating
intestinal dysfunctions (Cummings et al., 1997; Gibson & Roberfroid, 1995; Gibson & Wang,
1994a, 1994b, 1994c; Gibson et al., 1995; Hartemink et al., 1997; Kleessen et al., 1994; Kleessen et al., 1997; Mitsuoka et al., 1987; Roberfroid et al., 1998; Rowland & Tanaka, 1993;
Terada et al., 1993; Wang & Gibson, 1993; Williams et al., 1994). As a consequence of a
European Commission-funded project on non-digestible oligosaccharides, the ENDO project
(DGXII AIRII-CT94-1095) (van Loo, et al., 1999) it was determined by consensus that there is
now strong scientific evidence, based on observations with over 100 volunteers differing in sex,
age, race and dietary habits, that B(2-->1)-type fructans are prebiotic (Roberfroid et al., 1998). In
addition, inulin used as a general human gastrointestinal aid (Paul, 1996), as a method of treating
ulcerative colitis (Garleb & Demichele, 1995) and to inhibit C. difficile infections (Garleb et al.,
1997) are defined in United States patents.
Several researchers have reported the selective fermentation of inulin from a variety of
sources and production processes as well as other NDO using in vitro and in vivo studies and
pure cultures of human colon microflora. Results from many of these researchers are
In review, Modler et al. (1990) and Roberfroid (1993) defined inulin as a good substrate for most Bacteroides and Bifidobacterium species, except Bifidobacterium bifidum and some strains of B. longum. Chain length is an important determinant for some specific species, due to their
inherent inulinase activity. McBain and Macfarlane (1997) used a three-stage fermentation
system to reproduce several nutritional and environmental characteristics of the proximal large
intestine and the distal colon. Bifidobacteria populations were stimulated within three hours of
FOS addition increasing by approximately 10-fold with 12 hours. Total anaerobic populations
and the B. fragilis group also increased as did peptostreptococci and enterococcal numbers.
| L. casei||V||+||+||-||-||+||+||-||-||-|
| B. thetaitotaomicron||+||+||+||-||+||+||+||V||+||+|
| B. vulgatus||+||+||-||+||+||+||V||+||+|
| B. ovatus||+||+||+||+||+||+||V||-||+|
| B. distasonis||+||+||+||-||+||+||+||V||+||+|
| E. limosum||-||-||-||-||-||-||-|
| E. faecium||+||+||+||+||V|
| C paraputrificum||-||-||+||-|
| C clostridiiforme||V||-||+||-||+||-||V||-||-|
| C difficile||-||-||-||-||-|
| C romosum||+||+||+||-||+||+||V||-||+|
| C butyricum||-||+||+||+||-||+||-||-|
Table 3: Utilization of Various NDOs by Selected Human Gut Bacteria*
*-Results from various studies involving oligosaccharides having comparable chemical composition were combined. When studies
and/or a majority of the strains showed positive or negative results, the strain is displayed as (+) or (-), respectively. Studies having
no agreement are displayed as (V). Data obtained using different methods are combined.
1) FOS = fructooligosaccharides (including kestose, nystose, fructosytnystose, neosugar, Profeed, Meioligo, oligofructose, INU inulin (including avg. DP 9-10 units), TOS = trans-galactosyloligosaccharides, GLL = 4'-galactosyllactose, IMO = isomaltooligosaccharides,
RAF = raffinose, LAT = lactulose, LOL = lactitol, PHGG = partially hydrolyzed guar gum. 2) Bifidobacterium bifidum negative for most oligosaccharides.
References: Mitsuoka et al., 1987; Marchetti, 1993b; Hayakawa et al., 1990; Tanaka et al., 1983 - Hartemink et al., 1994; Hartemink et al., 1997; Saito et al., 1992; Yanahira et al., 1995, Asano et al., 1994; Kitler et al., 1992.
Clostridium perfringens increased transiently while fusobacterial populations were suppressed.
These researchers also studied the affect of FOS on enzymes capable of metabolizing a wide
range of compounds in the diet to form toxic, mutagenic and carcinogenic products. They found
that the addition of FOS caused increases in the production of arylsulphatase with B-glucosidase and B-glucuronidase showing a small decrease 3 hours following addition of FOS. These studies
highlight the complexity of the human intestinal microbiota and the potential problems that could
be encountered in changing its metabolism. They concluded that, even though there was some
synthesis of putatively 'genotoxic enzymes' carbohydrate administration should not be viewed as
Wang and Gibson (1993) and Gibson and Wang (I 994a) while working in vitro with
several Bifidobacteria strains, Cl. perfringens and E. coli, demonstrated that native chicory inulin (modal DP 10 units) allowed more rapid development of B. infantis, B. pseudolongum and B. angulatum as compared to glucose. B. longum had a slower development in comparison to
glucose, and the development of four other species was not significantly different. Inulin (modal
10 DP units) was demonstrated to significantly suppress the growth of both E. coli and C. perfringens. During the fermentation of inulin, mainly C02, medial H2 and relatively no CH4
Saito, Takano, and Rowland (1992) performed an in vitro fermentation study with
monocultures of 125 strains of human intestinal bacteria of 18 different genera, including 29
strains from 5 species of Bifidobacterium on media containing 5 different carbohydrate
substrates: refined soybean oligosaccharides, stachyose, raffinose, fructooligosaccharide or
glucose. The multiple unit carbohydrate sources elicited a slower growth rate than glucose for Lactobacillus, Bacteroides, and Enterococcus and did not support the growth of potential
pathogenic Clostridium species, Veillonella, E. coli, and klebsiella. The growth rate of Bifidobacterium, except B. bifidus, was similar on all carbohydrate sources. It should be noted
that Wada (1990) identified raffinose as a fermentation substrate for C. perfringens.
In vitro study using B. infantis and B. breve, and various inulin fractions showed that inulin (DP > 15 modal value of 22 units) induced a slower growth rate than glucose or lactose for B. infantis (Yazawa and Tamura, 1982). The reported data emphasized that the molecular
weight of a carbohydrate be relatively large and that its reducing end be occupied by fructose to
selectively grow bifidobacteria. Bacterial generation times were equal for inulin fractions,
irrespective of the molecular weight (from 1200 to 4500). It was further shown that B. infantis required about 4 hours for adaptation to these substrates. Consequently, when inulin is used as
substrate with B. infantis, the bifidobacteria should be adapted to it and ingested at the same
time (Yazawa - Tamura, 1982).
McKellar et al. (1993) characterizing the growth and inulinase production by Bifidobacteria spp. on fructooligosaccharides observed these strains to grow equally well on
short-chain fructooligosaccharides (average DP 3.7) and inulin as a native extract of chicory root
(modal DP 10 monomer units). Several strains of animal origin (B. thermophilum, B. minimum,
and B. cuniculi) grew significantly better than strains from human origin on inulin (DP > 15,
modal value of 22 units).
Several references identified Klebsiella pneumoniae as an inefficient or non-inulin fermenter (Brenner, 1980,- McKellar, Modler, - Mullin, 1993; Yazawa - Tamura, 1982). The
relative growth parameters of K. pneumoniae are chain dependent, as the organism does not
possess highly active intracellular 2,1 P-D-fructan-fructanohydrolase (EC 188.8.131.52) enzyme. As
analytical grade, long chain inulin (DP > 15, modal value of 22 units) has typically been used as
control substrate in research and for identification of K. pneumoniae. Negative growth data is
widely reported for this organism. The pathogen K. pneumoniae is indicated as growing well on
short chain fructooligosaccharides, I-kestose, nystose, fructosylnystose, and FOS synthesized
from sucrose and composed of GFm [n=B(2-1) linked fructose moieties bound to a glucose
molecule; 2< n <41 (Mitsuoka et al., 1987).
In addition to bacteria, some yeasts also have active exo-inulinase enzyme to break the
2, 1 - of inulin. They can potentially grow in periods following antibiotic therapy or in
individuals that are immune-compromised. Further, dietary habits can also alter normally
healthy gut microflora and create situations for opportunistic yeast overgrowth, cause thrush in
breast feed infants, and other health problems related to candidiasis. However, because yeasts
are primarily opportunistic pathogens their overgrowth is normally controlled and candidiasis prevented by competition provided from healthy, lactic acid producing organisms that are
nourished selectively by inulin. Of approximately 590 species of yeasts only 13 have clinical
significance and only five of the 13 have positive or variable growth on inulin (Barnett et al.,
1990), Table 4.
|Organism||Growth response* |
|Candida glabrata||- |
|Candida parapsilosis||- |
|Candida tropicalis||- |
|Cryptococcus albidus||- |
|Cryptococcus laurentii||V |
|Filobasidiefla neoformans||V |
|Kluyveromyces marxianus||V |
|Pichia gulliermondii||+ |
|Rhodotroula mucilaginosa||V |
Table 4. Yeasts most commonly isolated clinically and their growth characteristics on inulin.
As for in vivo studies, Bornet and others (1997b) working with a short-chain inulin fraction (average DP 3.7) observed fecal bifidobacteria increases in healthy humans is dose-response related. They noted that doses of 5 and 10 g/d significantly increased colonic bifidobacteria (p<0.05) while doses equal to or less than 2.5 g/d showed no statistically
significant modification effects. In a related study, twelve elderly adults, aged 69 ± 2 yrs,
ingested 8 g/d for 4 weeks and had bifidobacteria counts increase from 8.52±0.26 to 9.17±0.17
log CFU/g (p<0.05) (Bornet et al., 1997a). However, Roberfroid et al. (1998) stated that log
increases in bifidobacteria counts do not necessarily correlate with daily doses administered, but
rather depends more on the initial number of bifidobacteria. Lower initial numbers of bifidobacteria have been shown to produce greater increases, irrespective of dose, within a range
of 4-20 grams or more per day. An increase of bifidobacteria less than one log unit is difficult
to assess, and the absolute increase in number of bifidobacteria is likely to be less important than
the statistical significance of the increase (Roberfroid et al., 1998).
Gibson et al. (1995) further showed humans consuming 15 grams/day Inulin (DP 2 to 60;
avg. 10 units) significantly (p<0.001) increased the bifidobacteria: from log10 9.2 to log10 10. 1
per gram in a two week period, rendering them the dominant population, Figure 8. The numbers
of-gram-positive cocci decreased from log10 6.0 to log10 5,5 (p<0.001); and the total aerobic and
anaerobic counts and the numbers of other groups of bacteria stayed at the same level. Buddington and others (1996) found that adding Neosugar to the diet of healthy subjects
increased anaerobes represented by bifidobacteria from 3.4% to 9.5%. Total aerobes and enterobacteria were less affected by Neosugar.
In a study to determine pre- and probiotic effects on intestinal microbial composition, Bouhnik, Flourie, Andnieux. et al. (1996) reported the prolonged ingestion of Bifildobacterium sp increased the proportion of bifidobacteria in the colonic flora of healthy human subjects. However, the concurrent administration of inulin did not enhance this effect. No changes in
fecal total anaerobe counts, pH, nitrate reductase, nitroreductase and azoreductase activities
were found in either group.
In another in vivo study involving 35 elderly female subjects, mean age of 76.4 years and
suffering from constipation, inulin was compared to lactose to determine effects on fecal microflora, microbial activity and bowel habit. Results showed a progressive increase in inulin ingestion from 20 g/d to 40 g/d for 19 days increased bifidobacteria significantly from 7.9 to 9.2 log10/g dry feces, and decreased enterococcl in number and frequency, while not changing the
total bacterial counts (Kleessen et al., 1997).
Inulin may also affect intestinal and hepatic enzymes important in the elimination of
toxic compounds from the body. Roland, Nugon-Baudon, Plinois, and Beaune (1994) found that
the specific activity of glutathione-S-transferase (GSH-T) in rats fed inulin was significantly
higher than in rats fed other dietary fibers. The effects on the zenobiotic-metabolizing enzymes
(XEM) could not be predicted based on the solubilities of the fibers. Buddington and others
(1996) supplemented a controlled diet of 12 healthy human subjects with four grams of Neosugar. Neosugar caused B-glucuronidase and glycocholic acid hydroxylase activities to
decrease by 75% and 90%, respectively. Nitroreductase activity declined by 80% after the
control diet was started but was not affected by neosugar. The responses by these three enzymes
suggest that they are regulated independently by different factors and processes, and respond
differently to diet composition.
Causey and others 2000b, in a double-blind cross-over human study involving 12 healthy
male volunteers on a controlled inulin (DP 2 to 60; avg. 9 units) diet (20 g/day), showed
significant increases in total anaerobes (control-1.98 ElO CFU ± 1.65 E10 vs. inulin-2.82 E10 1.79 E10, p=0.03) and lactobacillus species (control-1.55 E09 ± 2.44 E09 vs. inutin-2.85 E09 -
4,30 E09, p=0.05) and a significant decrease in fecal ammomia levels (control-87.50 ± 42.90 vs.
51.50 ± 28.68 ppm, p=0.001) and B-glucuronidase activity (control-15.49 ± 3.94 vs. inulin-10.51
± 4.34 umol/L*g*h; p=0.02). The study further showed a trend toward decreased B-glucosidase,
fecal pH, clostridia and enterobacteriaceae species. Glycocholic acid hydroxylase activity was
unchanged by chronic inulin consumption.
III. (b). Products of Fermentation. Upon reaching the large intestine inulin is preferentially utilized by a group of healthy bacteria, bifidobacteria and lactobacilli, that are present in the ceco-colon. During the fermentation process, energy is provided for bacterial proliferation and
increased cell mass. A few species of lactobacilli produce carbon dioxide gas during their
fermentation (Hartemink & Rombouts, 1997). Bifidobacteria have not been found to produce
hydrogen or carbon dioxide (Holdeman & Moore, 1977). The bacterial mass and gas production
are metabolically of no benefit to the host. Gas production from inulin is likely a result of its
fermentation by strict anaerobic species, such as bacteroides, some non- species of
clostridia and yeasts, anaerobic cocci, and some species of lactobacilli. The hydrogen and
carbon dioxide produced from these bacteria may be further metabolized to methane by methanogenic bacteria (Wolin & Miller, 1983). However, Roland, Nugon-Baudon, Andrieux and Szylit (1995) found that rats colonized with human fecal microflora and fed inulin at 116 g/kg/feed produced almost no methane but significantly more hydrogen gas.
In addition to these fermentation products, short-chain fatty acids (SCFA), acetate, proplonate, and butyrate are also formed along with L-(+)-lactate. Rats consuming inulin had significantly higher production of short chain fatty acids (SCFA) in the cecum (p<0.05) in comparison to other fibers tested: wheat bran, pea hull, oat husk, cocoa seed and carrot fiber
(Roland, Nugon-Baudon, Andrieux et al., 1995). SCFAs are important anions in the colonic
lumen, affecting both colonocyte morphology and function. By stimulating sodium and water absorption, SFCAS act to minimize effects due to diarrhea. SCFAS may enhance ileal motility and increase intestinal cell proliferation by local action and by increasing mucosal blood flow (Scheppach, 1994), Figure 9.
Figure 9: Factual and Hypothetical Effects of Short Chain Fatty Acids (SCFAS) on Colonic Morphology and Function, from Scheppach 1994
In addition to their effects on gut morphology and function, the SCFAS are absorbed through the colonic epithelial cells into the portal blood, thus becoming a source for host energy and regulators of several metabolic processes, Figure 10.
Figure 10: Scematic of the bioavailability of digestible carbohydrates and inulin
Butyrate, remaining from colonic metabolism, propionate and Lt-l-lactate enter the liver from the portal blood and are completely metabolized. Propionate is transformed into methylmalonyl-SCoA and then succinyl-coA. L(+)-lactate is the precursor in gluconeogenesis. The small amount of butyrate reaching the liver is a precursor in lipogenesis (Roberfroid and Delzenne, 1993). About 50-75% of acetate is metabolized in the liver to produce energy, and like butyrate, serves as a lipogenic substrate. The remaining acetate fraction passes into peripheral muscle tissue where it is metabolized (Roberfroid & Delzenne, 1993).
The ratios of individual SCFA are likely very important as each SCFA impacts host metabolism differently. Propionate has been demonstrated to lower cholesterol synthesis, both in vitro in isolated rat hepatocytes (Demigni et a1., 1995; Nishina & Freeland, 1990; Wright et al., 1990) and in vivo in rats (Chen et al., 1984; ullman et al., 1988) and in humans (Wolever et a1., 1995), likely by inhibiting gluconeogenesis, stimulating glycolysis and inhibiting biosynthesis of fatty acids. Conversely, acetate stimulates gluconeogenesis (Rimisy et al., 1992b), inhibits glycolysis, and is a well known precursor of cholesterol (Nilsson & Belfrage 1978).
Butyrate and, less efficiently, propionate affect colonocytes at various stages of the adenoma-carcinoma-sequence. Butyrate has also been shown to be the preferred energy substrate for the colonocyte, accounting for about 70% of total energy consumption, and to be a potent differentiating agent in cell culture (Rimisy et a1., 1992b; Roediger, 1980; Scheppach, 1994). Butyrate and to a lesser extent, propionate may also have a role in preventing certain types of colitis (Scheppach, 1994; Scheppach, 1998). The SCFA may also inhibit proliferation of colon cancer cells, probably by causing an arrest at the early G1 phase by causing an arrest at the early G1 phase (Scheppach, 1998).
The SCFA (acetate/propionate) ratio resulting from colonic fermentation of inulin appears quite favorable for modulating carbohydrates and lowering cholesterol. Botham and others (1998) working in vitro with human fecal slurries showed inulin fermentation provided the highest propionate/acetate ratio of NDOs tested and a relatively high butyrate level, Figures 1 la and 1 lb. The work also showed that the chemical structure effects the dependability of a fiber: cellulose with B-1,4 bound glucose as the primary structure is hardly fermented, while starch with both a-1,4 and a-1,6 linked glucose units is much more suspectable. It is also clear that amylase film is little fermented due to the limited accessibility to fermentative enzymes, whereas an amylose gel having a much better access for enzymes is fermented to a larger extent Further, this ratio may be somwhat dose dependent as shown in vitro using rat heptocytes.
Levrat and coworkers (1991) further showed that higher inulin concentrations, up to 10% of the diet, favored higher propionate levels and a SCFA ratio of approximately 42:38:20 percent, acetate, propionate, and butyrate respectively. However, while a dose relationship for inulin is suggested from in vitro study, no dose-effect relationship has yet been determined in vivo with human volunteers (Roberfroid et al., 1998). Rather, significant bifidobacteria-stimulating effects have occurred at a human consumption level of 15 grams/day using native inulin extracted from chicory (Gibson et al., 1995). However, based on available literature, the threshold consumption level at which these effects begin to be significant is likely about 4 grams/day.
Figure 11a: Short chain fatty acids levels after 24 hours in vitro fermentation, Botham et at. 1998.
In terms of carbon units, the overall balance from fermentation of 1 mol fructosyl unit of inulin produces about 40 percent SCFA (mol-ratio: acetate 81:propionate 13:butyrate 6), 15 percent L(+)-lactate and 5 percent C02 and up to 40 percent bacterial biomass, predominately
bifidobacteria (Roberfroid & Delzenne, 1993).
It has been shown that the activity of microbial inulinases, which are the necessary enzymes for inulin fermentation and SCFA production and gas production, is influenced in vitro by the degree of polymerization (Roberfroid et al., 1998). Insulin is reported to produce much more favorable mean SCFA/gas volume ratio (10.8) than shorter chain FOS (7.8) or non- preferential NDOs [soy polysaccharide (8.7), resistant starch (7.2), or arabic gums (8.-)].
Figure 11b: SCFA levels and ratios after 24 hours in vitro fermentation, Botham et at. 1998
Fiber-NDO mixtures have been shown in vitro to provide the highest SCFA/gas volume ratios (13.5), while inulin produced the highest concentration of total SCFA over the fermentation period (5.8 mMol/g inulin vs. 5.2 mMol/g fiber-NDO mixture, Figure 12 (van Hoeij, Green, Pijnen, Speckmann, & Bindels, 1997). Favorable SCFA/gas ratio indicates that inulin only results in modest gas production while producing relatively high quantities of the SCFA, an important factor in patient tolerance for supplemented enteral nutrition formula (van Hoeij et al., 1997). The rate of fermentation also defines intestinal tolerance and SCFA-mediated systemic responses such as mineral absorption, carbohydrate and lipid effects, and osmotic taxation (Roberfroid et al., 1998).
Figure 12: Short chain fatty acid and gas production of individual NDO, polysaccharides, and their mixtures, from Van Hoeij et al. 1997.
IV. (a). Carbohydrates and Dietary Fiber. The 1,2 - and 2,6-B-linkages making up inulin are resistant to mammalian digestive enzymes; such as the disaccharidases (sucrase, maltase, isomaltase,or lactase) of intestinal mucosa and a-amylase of pancreatic homogenates (Oku et al.,
1984). Consequently, inulin reaches the colon virtually unaltered. The shorter chain fractions of fructooligosaccharides are also neither hydrolyzed nor absorbed from the small intestine (Tsuji et al., 1986).
Glucose tolerance tests conducted on human subjects who consumed either 50 g of
sucrose or 25 g of fructooligosaccharide after a 15 hour overnight fast showed no change in
either blood insulin or glucose levels when the fructooligosaccharides were used (Hidaka, Eida,
Takizawa, Tokunaga, & Tashiro, 1986). The mechanism of this effect may be explained by the
effect of inulin on glucose uptake itself (Kim & Shin, 1996). An intestinal perfusion technique
with rats measured both jejunal and ileal uptake of glucose when inulin and chicory extract was
also present. Over 30 minutes, jejunal and ileal segments were perfused with an isotomic electrolyte solution (pH 7.4) which contained glucose (10 mmol/L) and inulin or chicory extract
(10g/L). Both chicory extract and inulin reduced the absorption rate of glucose from the rat
Jejunum (p<0.05) but not the ileum. The percent of overall glucose absorption was also
significantly reduced from the rat Jejunum. when inulin or chicory extract was present as
compared to controls (p<0.05).
Inulin is compared with soluble-viscous-fermentable dietary fibers since it is not
hydrolyzed by the human digestive system but is hydrolyzed and fermented by colonic microflora, which affects systemic physiological functions. Since inulin does not possess the
typical physical properties of soluble-viscous dietary fibers to bind water in the upper CTI, it does
not significantly reduce digestive transit time. However, as mentioned, inulin may have
significant systemic influence to effect glucose absorption, most likely by influencing gut inulin-like incretins and hepatic enzymes (see sections on lipid metabolism and diabetes). Inulin is defined as a "functional food", a food when consumed in the course of the daily diet, has specific physiological benefits. According to Roberfroid (1993) and Prosky (1999), these
characteristics should allow inulin to be classified as a unique soluble dietary fiber.
Because the Food and Drug Administration (FDA) and the United States Department of
Agriculture (USDA) have defined dietary fiber as material that precipitates in 78% ethanol, inulin and FOS, being soluble in 78% ethanol, are not currently classified as dietary fiber for labeling purposes. This definition is under review, however, and will include inulin and FOS in the future- Official AOAC analytical methods (Nos. 997.08 and 999.03) are approved to
quantify the B(2-->1) fructans as part of the soluble dietary fiber complex in foods and food
products (Hoebregs, 1997; Kennedy, 1999). To date, inulin and oligofructose have been
accepted as dietary fiber in sixteen countries (United Kingdom, Austria, Belgium, Denmark,
France, Germany, Greece, Ireland, Italy, Netherlands, Norway, Finland, Sweden, South Africa,
Portugal and Switzerland) with approvals pending in three other countries besides the United
States (Spain, Canada and Australia) (Tungland, 1999).
A physiological definition of dietary fiber combines the nutritional criteria of nondigestibility with the physiological effects that are associated with regular intake of dietary fiber.
Potential physiological effects attributed to nondigestible carbohydrates include both local and
systemic effects (Jenkins, Kendall, & Vuksan, 1999) as outlined in Table 5.
|Local Effects||Systemic Effects|
|^ Fecal bulking||v (^) Cholesterol|
|^ Bacteria||v TG (v insulin, v blood glucose)|
|Selective ^ bacteria||v Blood ammonia levels|
|^ SCFA production||v Urea|
|Selective ^ in SCFA||^ B-vitamins|
|^ Mineral absorption||^ Immune function|
|^ B-vitamin synthesis||^ glutamine?|
1- Abbreviations: SCFA, short chain fatty acids;
TG: triglyceride (Jenkins et al., 1999)
^ = increase; v = decrease
Table 5. Potential effects of nonabsorbable carbohydrates: physiological effects1
IV. (b). Caloric Value. Longer chain native oligosaccharides (Inulin) and shorter chain
synthetic fructooligosaccharides (Neosugar)-GF2,GF3,GF4 reach the large intestine virtually
intact and, as such, were considered not to be a major source of energy (Oku et al., 1984).
Furthermore, in the rat model, there appear to be no hydrolytic enzymatic adjustments in the
small intestine to long-term ingestion of these factors. Nilsson and others (1988) used oral intubation to give fructans with a DP of about 9 or DP 16 to rats and found that both proceeded
as undigested material through the gastrointestinal tract to the colon. However, due to the
bacterial fermentation that occurs in the colon, these oligosaccharides do contribute to the
energy pool. The caloric value of a fructosyl unit of oligofructose is calculated at 30 to 40% of a
digested fructose molecule or between 1- 1. 5 kcal/g (Roberfroid et al., 1993). Ranhotra and
coworkers (1993) reported a caloric value for oligofructose of 1.48 kcal/g. They determined
usable energy value based on efficiency of conversion of gross food energy to net energy
(carcass energy) using young rats as the test model. Molls and others (1996) further defined the
energy value of fructooligosaccharides (44% GF2; 46% GF3; and 10% GF4) working with six
healthy human subjects. Calculated mean energy value of the fructooligosaccharlde was 9.5+0.6
kJ/g (range: 8.3-11.7 kJ/g) or about 2 kcal/gram. For nutrition labeling purposes, Roberfoid (1999) recommends that inulin and oligofructose, as well as all nondigestible oligosaccharides
that are mostly fermented in the colon, be assigned a caloric value of 1.5 kcal/g (6.3 kJ/g).
IV. (c). Lipids. A commonly referenced systemic effect of inulin is that related to lipid
metabolism. Most animal studies have shown that inulin has an effect on blood lipid levels.
Daily feeding of oligofructose (mean DP of 4.8) to rats at a 10% dose level resulted in significant
serum triglyceride lowering after just one week of feeding (Flordallso et al., 1995). Serum
triglycerides in the oligofructose-fed rats continued to remain significantly lower than controlfed rats for an additional 12 weeks of feeding. The decrease in serum triglyceride levels was
apparently not due to increased fecal excretion since fecal levels remained unchanged
throughout the study. Tokunaga and coworkers (1986) had also shown that rats fed 10% or 29% fructooligosaccharide (GF2-GF4) diets experienced lowered serum triacylglycerol levels. In
contrast, however, they failed to show reduced serum cholesterol levels whereas Fiordaliso's group was able to show significantly reduced serum phospolipids and total cholesterol levels in oligofructose-fed rats. Reduced serum triglycerides, phospholipids; and total cholesterol were
mainly due to a decreased number of very low density lipoprotein (VLDL) particles, and not the
low density (LDL) or high density lipoprotein (HDL) fraction. Trautwein and coworkers (1998)
have reported similar findings in hamsters fed 16% inulin diets for five weeks. These works
have suggested that oligofructose (inulin) feeding alters hepatic lipid metabolism which results in
less VLDL production.
In confirmation of the work by Fiordaliso and others (1995), Kok et al., (1996b) were
able to demonstrate a significant decrease in serum triglyceride-VLDL when 10% oligofructose (inulin) (DP = 4.8) was given in a standard diet for rats. Since liver enzyme activity was also
reduced for two of the four enzymes assayed, it is probable that SCFA produced from oligofructose fermentation decreased liver capacity for de novo trglyceride and fatty acid
synthesis through inhibition of key enzyme activities, particularly glycerol-3-phosphate acyltransferase and fatty acid synthase.
It has been suggested that oligofructose and inulin may have the ability to protect against
or modify liver lipid accumulation that is induced by another nutrient such as fructose when fed
at the same time (Kok et al., 1996). An additional study has indicated that oligofructose supplementation can reduce postprandial hypertriglyceridemia when fed with a high fat diet
(Kok et al., 1998). The effect, however was only on circulating triglycerides and phospholpids,
rather than liver lipids. Feeding oligofructose with a high fat diet did not prevent the hepatic
accumulation of triglycerides, phospholipids and cholesterol that is prompted by a high fat diet
but the livers of rats fed high fat-oligofructose diets displayed smaller lipid droplets as compared
to rats fed a high fat diet only.
Fructooligosaccharide (inulin) effect on lipid metabolism in humans may vary,
depending on the presence or absence of chronic disease. A human study with diabetic subjects
was conducted over a 14 day period in which 8 g of fructooligosaccharides were ingested in a
coffee drink or coffee jelly. Over the course of the study mean serum total cholesterol levels
were reduced by 19 mg/dl (242±43 mg/dl vs. 223±27 mg/dl, p<0.01) and LDL-cholesterol levels
by 17 mg/dl (164±33mg/dl vs. 147±32 mg/dl, p<0.02) (Yamashita et at., 1984). Serum HDLcholesterol,
triglycerides and free fatty acid levels in these diabetic subjects were not
significantly affected by the consumption.
In a double-blind crossover human study involving 12 slightly hypercholesterolemic men, Causey and others (2000) showed serum triglyceride reduction of 40 mg/dL (282.92
control, 243.24 inulin, p = 0.024) when 20 grams/day of chicory inulin (DP 2 to 60; avg. 9 units)
was consumed. Total serum cholesterol was also reduced 11 mg/dL (240.8 control; 229.8 inulin; p = 0.086. LDL-cholesterol also showed reduction, albeit, not significant. No change in HDL was noted, Figure 13.
Figure 13: Effect of Inulin Ingestion on Lipid Metabolism, from Causey et al. 1998a.
Another crossover study, involving twenty-one hypercholesterolemic men and women
ingesting 18 g/day chicory inulin (DP 2 to 60; avg. 9 units) on a low-fat diet, showed statistically
significant (P <0.05) reductions for LDL-C (-4.4%) and total cholesterol (-8.7%), respectively
(Davidson et al., 1998). No effects on HDL cholesterol or serum triglyceride were noted. Yet,
in another study, Davidson and Maki (1999) reported on the serum lipid profile of 25 adults with
mild-to-moderate hypercholesterolemia who were fed 18 g/day of chicory inulin as a substitute
for the sugar content of study foods. The study was a random, double-blind, crossover design
with six week study periods and a six week washout period. At the end of both study periods,
serum lipids (LDL-C, HDL-C, total cholesterol and triglycerides) were not significantly different
between experimental and control groups. Because serum total cholesterol and LDL-C were
higher at the beginning of the control phase than at the beginning of the inulin phase, the results
of this study were difficult to interpret. The study was unable to add more evidence regarding
the lipid lower effects of inulin. It did, however, provide some evidence indicating that daily
consumption of 18 g of chicory inulin resulted in more mild gastrointestinal discomfort than
during the control food phase (Davidson et al., 1999). The mild discomfort was experienced and
reported throughout the entire 6 weeks of inulin treatment.
In healthy human populations the effects of inulin and oligofructose are more mixed. Canzi and others (1995, 1999) observed that daily intake of inulin (9g/d) in a rice-based ready to-eat
cereal by 12 normolipidemic men resulted in significant reductions (p<0.05) in serum triacylglycerol and LDL- levels, 20.4 mg/dL and 8 mg/dL, respectively. However,
Pederson and coworkers (1997) observed no effect with inulin in a low fat spread (14g/d)
consumed by a group of 64 healthy normolipidemic women over a four-week double-blind
crossover study. Williams (1999) reported on a study by Jackson et al. (1999), in which fifty-four healthy but slightly hyperlipidemic adults consumed 10 g/day of long-chain chicory inulin (DP 15 to 60; avg. 22 units) for an eight-week period. There were no effects on cholesterol, but
fasting serum tri acylglycerols (- 19% after 8 weeks) and insulin levels (- 17% after 4 weeks and - 10% after 8 weeks) dropped significantly (p<0.05). Although not significant, a trend towards
decrease total and LDL cholesterol was also observed. HDL cholesterol levels remained
unchanged in both inulin-fed and control groups. These results were similar to those reported by Luo and others (1996) when healthy male subjects consumed 20 g short-chained fructooligosaccharides for four week periods in a double blind crossover design. Serum triglycerides, total and HDL cholesterol remained unchanged after four weeks of feeding inulin.
Possible mechanisms for the lipid lowering effects have been proposed. Ellegard and
coworkers (1997) found that neither cholesterol absorption nor excretion from the small intestine
was affected in ileostomy patients when either 17.1 g inulin or 15.5 g oligofructose was fed.
They proposed that a lipid lowering effect may happen by another route, such as propionate
absorption from the colon, which could suppress hepatic synthesis. As previously mentioned,
short chain fatty acids, particularly propionate, influence carbohydrate and lipid metabolism.
Propionate has been demonstrated to lower cholesterol synthesis (Chen et al., 1984; Demigne et
al., 1995; Illman et al., 1988; Nishina & Freeland, 1990; Wnight et al., 1990; Wolever et al.,
1995). Others propose that some bifidobacteria and lactobacilli in fermented products are able
to remove cholesterol (van Poppel & Schaafsma, 1996).
Like other NDOs, inulin could suppress serum cholesterol through an enhanced secretion
of bile acids (Kim & Shin, 1998; Mazur et al., 1990; Trautwein et al., 1998). In addition, inulin could decrease the serum cholesterol level by reducing hepatic cholesterol synthesis through
inhibition of HMG-CoA reductase activity, with subsequent effects on concentration of B- hydroxy-B-methylglutaryl CoA (HMG-CoA) the key cholesterol intermediate.
As for the triglyceride lowering effect Delzenne and Kok (1999), in confirmation of
earlier in vivo and in vitro rat studies, again reinforced the concept that short chain fatty acids
produced from oligofructose (inulin) fermentation exerts a triglyceride-lowering action primarily
due to a reduction of de novo fatty acid synthesis in the liver, through inhibition of all lipogenic
enzymes. This suggested that inulin decreases lipogenic enzyme gene expression.
Yet another route inulin and oligofructose may decrease serum lipid levels is via lowered
serum insulin and glucose, both known to regulate lipogenesis. Kok and coworkers (1998b)
postulated that the lower glucose and insulin levels that were found after feeding a dose of oligofructose 10 g/100 g to rats contributed to the reduced hepatic fatty acid and triglyceride
synthesis, and are part of the mechanism of the hypolipidemic effect of oligofructose. The
researchers suggest that cecal hypertrophy resulting from SCFA is also likely to positively
influence lipid metabolism by increasing the secretion of intestinal incretins, namely, glucosedependent insulinotropic polypeptide (GIP) and glucagon-like peptide-I (GLP-1). These gut
hormones are known to regulate postprandial insulin release and also to have direct insulin-like
actions on lipid metabolism (Morgon, 1996). Inulin has been shown to reduce postprandial glycemia and insulinemia by 17 % and 26%, repectively (Kok, et al. 1996).
While the effects of inulin and oligofructose on lipid metabolism in animals tend to be
more concrete and consistent, the determination of consistent lipid lowering effects for inulin and oligofructose in humans is yet to be confirmed. It appears that hyperlipidemic subjects are
more likely to experience a reduction in serum cholesterol levels when inulin is ingested but
normal subjects are more prone to reductions in serum triglyceride levels. A number of factors
need to be considered including: individual variation, duration of administration of inulin or oligofructose, fermentation rates of the various chain fractions, intakes of dietary fat and
carbohydrate in the background diet; and prior serum lipid levels (Williams, 1999). Part of the
reason for the discrepancy in results between animal and human studies may be the inulin dose
level used in animal studies is much higher than the level used in human studies. The dose
levels used in animal studies are not likely to be well tolerated by humans.
IV. (d). Minerals. Although cereal fiber and its associated phytate content have been found to
depress the absorption and retention of several minerals (Greger, 1999), it has been hypothesized
that fermentable carbohydrates, like inulin, could possibly improve the metabolic absorption of
certain minerals such as calcium, magnesium and iron (Campbell et al., 1997; Lopez et al., 1998; Scharrer & Lutz, 1990; Schulz et al., 1993). Ohta et al. (I 995b, 1997a) and Baba et al. (1996)
formulated the hypothesis that the effects of NDO on calcium and magnesium absorption occur
at the level of the large intestine, a new concept, as it is generally accepted that mineral
absorption occurs mainly via the small intestine. The mechanism for this improvement is
speculated to be the production of SCFA and lactate resulting from inulin fermentation in the
colon, which in turn results in a reduction in luminal pH with corresponding increase in the
mineral free ionic form, solubility and bioavailability. The lower luminal pH raises the
concentration of ionized minerals and accelerates passive diffusion (Remesy, et al., 1992a).
In particular, the accumulation of calcium phosphate in the large intestine and the solubilization of minerals by SCFAs are likely to play an essential role in the enhancement of
mineral absorption (Rdmdsy et al., 1993; Kashimura et al., 1996). In experiments conducted by Levrat and others (1991) using rats fed a diet supplemented with a 10% inulin fraction, the cecal pool for calcium, magnesium and phosphate was improved. Furthermore, feeding of fructooligosaccharides to animals has led to reduced fecal excretion of minerals. As an example, Ohta et al., (1994a) fed fructooligosaccharides to male Sprague-Dawley rats that were also
consuming two levels of magnesium while maintaining constant and sufficient levels of calcium
and phosphorous. Under low magnesium intake, fructooligosacchari des were able to increase
magnesium absorption and reduced the occurrence of auricular and facial peripheral hyperemia
and hemorrhage, both signs of magnesium deficiency. When 5% fructooligosaccharides were
fed to rats on low magnesium diets, they began to absorb magnesium at approximately 3.0 mg
per day, which was similar to rats fed magnesium-sufficient diets.
Further work on the question of fructooligosaccharide effect on mineral absorption has
also demonstrated improved calcium (Morohashi et al., 1998), and calcium and magnesium
absorption (Ohta et al., 1994a, Ohta et al., 1995b) in normal rats. Even following gastrectomy,
rats fed FOS were found to have greater net calcium absorption than rats fed a control diet (Ohta et al., 1998b). In cecectomized rats, however, only magnesium absorption was improved (Ohta et al., 1994b). This finding, in particular, suggested that colonic fermentation is particularly
important for calcium absorption. In addition, relative amounts of calcium binding protein
(calbindin-D9k) were increased in the large intestine and decreased in the small intestine in rats
fed fructooligosacchari des (Ohta et al., 1998a). Since calcium binding protein concentration and
calcium absorption were positively correlated in large intestine segments, observations from this
latter study suggest FOS exerted an independent stimulatory effect on calcium absorption from
the large intestine via a transcellular route involving calcium binding protein as well as a
diffusive, paracellular route.
When focussing on iron, Ohta and others (1995a) investigated the effects of fructooligosaccharides on mineral absorption in rats that were made anemic prior to the study.
Male Sprague-Dawley rats were fed 5% fructooligosaccharides with either 15 mg Fe/kg diet (low
iron intake) or 30 mg Fe/kg diet. Magnesium, calcium and iron absorption were measured. Fructooligosaccharide feeding reduced the cecal pH, increased iron, calcium and magnesium
solubility in the cecal contents, and increased iron, calcium and magnesium absorption.
Furthermore, iron levels did not affect calcium or magnesium absorption when fructooligosaccharides were included in the diet. Thus, fructooligosaccharides may be helpful in
correcting iron deficiency anemia while also increasing the absorption of calcium and
magnesium. Correction of iron- anemia in post-gastrectomized rats fed a 7.5% FOS
diet for six weeks has also been demonstrated (Ohta et al., 1998c)
Delzenne and coworkers (1995) concluded rats fed a diet containing higher levels of inulin (10% inulin) also lead to a significant increase (of about 60%) in the apparent retention of
calcium magnesium, and iron, Figure 14. The rat study further showed inulin increased fecal
excretion and decreased urinary excretion of nitrogen. Thus, inulin may provide a good means to
counteract dysfunctions resulting from hyperammonemia or disturbed iron, calcium, magnesium
and zinc homeostasis (Delzenne et al., 1995). A similar increase (about 65%) in calcium
abolition was also observed by Brommage and others (1993) with rats fed a diet supplemented
with 5% |iuctooligosaccharides or other Mrs. A study by Taguchi et at. (1995) showed that
oligofructse (2.5 and 5% in the diet) increases calcium and magnesium absorption in
ovariectomized rats (a model to typify post-menopausal women). The study further showed that
the supplementation prevented bone loss caused by estrogen deficiency. Scholz-Ahrens, using
the sample modeling technique, reported a dose-effect of oligofiuctose (2.5, 5 and 10% in the
diet) on the increase of both calcium absorption and bone minimization (bone calcium content)
in femur and lumbar vertebra, confirming an increase in calcium uptake into bone tissue by
fiutan ingestion. This opens the direction to considering consumption of inulin to reduce the
risk of osteoporosis. This effect was further consumed by Lemort and others (1997) using
unaltered rats fed a diet containing either 5 or 10% of inulin (DP >15; avg. 22 units).
In human studies County and coworkers (1997), using nine healthy men. showed
significant improvements (p<0.05) of calcium absorption and balance (+91.8 mid) compared to
control upon chicory inulin ingestion up to 40 g/day. The apparent calcium absorption increased
from 21.3% ± 12.5) to 33.7% (±12.1), representing a relative increase of 58%. The increase in
calcium absorption did not negatively alter the absorption of other minerals such as magnesium,
iron and zinc. Ellegard and coworkers (1997) using mineral balance showed that in ileostomy
subjects consuming 17 g/d inuring the inulin did not influence the absorption of calcium in the
small intestine, making it likely that, in humans as in animals, a positive effect on calcium
balance is dependent on colonic activity. Van den Heuvel and others (1998) validated a stable
isotope technique in determining intestinal calcium (and iron) absorption in humans. The study
involving healthy young adults consuming 15 g/ day of a placebo, inulin or oligofructose showed
no significant differences in mineral absorption after a 24-hour calcium isotope collection period
from urine. It was determined that the 24-hour urine collection period may be too short to make
a complete balance and identify an effect due to fructan intake, However, the experiment
confirmed that fructans have no adverse effects on calcium absorption. Following this study,
van den Heuvel et at, (1999) performed a similar study using stable isotopes, increasing the urine
collection time from 24 hours to 36 hours, A group of twelve healthy male adolescents
volunteers consumed 15 day of either oligofructose or a placebo (sucrose) for one week.
Results showed a significant increase (±26%; p<0.05) in the Sectional calcium absorption when
comparing the placebo group (47.8%) to the oligofructose treatment group (60.1%).
Figure 14: Effect of full on Mineral Absorption adapted from Delzene et aL 1995.
Food fibers are suspected of interfering with mineral bioavailability. When resistant
starch or oligosaccharides were fed, however, phytic acids impact on mineral absorption is
lessened (Lopez et a1., 1998), possibly due to the intestinal fermentation that occurs in the large
intestine when oligosaccharides are present, This was especially true for calcium, magnesium,
zinc, iron and copper. Although precise mechanisms for absorptive action on minerals still
require clarification, it will be important to consider that absorptive mechanisms for minerals
may vary with the mineral and the type or amount of nondigestible carbohydrate (Greyer, 1999).
IV. (e). Vitamins. Bifidobacteria synthesize many of the B vitamins (thiamin, folic acid,
nicotinic acid, pyridoxine and vitamin R12) (Deguchi et a1., 1985). Since bifidobacteria are
present in human intestinal flora, they may be a significant source of the B complex vitamin
supply. Whether or not the stimulation of bifidobacteria growth by inulin and oligof-uutose
results in further synthesis and availability of the B vitamins in humans is yet to be confirmed.
V. HEALTH IMPLICATIONS
V. (a). Cancer, Cancer continues to be the number one health concern of Americans (Sloan,
1999), Most cancers strike both men and women at about the same rate, with exception of
cancers of the reproductive system. The incidence of cancers, other than prostate (or those that
potentially may be favorably influenced by specific dietary fibers), is expected to increase 31%
in the 50-64 year old age bracket by 2005. Surveys indicate that 60% of the consumers are more
likely to believe nutrition, particularly that supplied by high soluble fiber containing bits,
vegetables and grains, has an effect on the prevention of colon cancer (Sloan, 1999).
The majority of colon cancer cases follow the so-called adenoma sequence: normal colon
cells undergo transformation as a result of cellular mutations. Hyperproliferation and aberrant
crypt foci develop and may progress to form small and then larger adenomas, which may
eventually transform into cancer. This entire sequence will usually last 15-20 years. Dietary
factors can influence this process in both positive and negative ways, Figure 15.
Figure 15. Normal colon mutual transformation via hyperproliferation and adenomas to carcinoma.
In a review of possible mechanistic effects for colon cancer inhibition, Reddy (1999)
emphasized the importance of examining both probiotic and prebiotic activity, with possible
synergistic effect when used together. Lactic cultures used in the fermentation of milk products
are examples of probiotics. These products have been shown to possess antimutagenic and
anticarcinogenic properties (Bodana & Rao, 1990; Goldin & Gorbach, 1980; Lidbeck et a1.,
1992). However, when fed, it is uncertain whether the viability is maintained throughout the
gastrointestinal system, until the lower gut is reached. lactic acid-producing bacteria like
bifidobacteria, are a predominant bacterial species in the gut (Gallaher & Khil, 1999). In
addition to lactic acid production these bacteria produce acetic acid and the combination of the
two help prevent growth of putrefactive bacteria (Rasic, 1983).
Prebiotic factors such as inulin and oligofructose are also able to selectively stimulate
growth of bifidobacteria at the expense of more putrefactive bacteria (Gibson & Roberfroid
1995). Furthermore, fermentation of these oligosaccharides in the colonic regions results in
production of short chain fatty acids (Roherfioid et al., 1993; Wang & Gibson, 1993). Butyric
acid has been shown to increase apoptosis in human colonic tumor cell lines (Hague et al., 1993;
Scheppach, 1995 & 1998). Apoptosis is a mechanism by which excess or redundant cells are
removed during development and restricted tissue size is maintained. Apoptosis is
thus an innate cellar defense against carinogenesis. Lactic acid production can lower intestinal
pH. There is evidence that increasing the numbers of bifidobacteria in the colon and reducing
intestinal pH has a direct impact on carcinogenesis in the large intestine (Goldin & Gorbach,
1980; Hill, 1988; Koo & Rao, 1991).
Possible mechanisms for the anticarcinogenic and antitumorigenic effect are not
completely understood. Among all of the possible mechanisms for the tumor inhibitory and
anticarcinogenic effect, more work needs to be done to establish which are essential to the
process (Taper & Roberfroid, 1999). It is possible that all or some are involved in a metabolic
chain reaction for the inhibitory effect to occur.
Modulation of the microflora through the stimulation of bitdobacteria while keeping E.
colt or clostridia at low levels is one possibility. Rulnney and Rowland (1995) suggested that
production of toxic metabolites may be reduced by increasing the proportion of more healthy
colonic microflora which compete with pathogenic and putrefactive bacteria to reduce the levels
of toxin and carcinogenic-producing enzymes, Figure 16.
Figure 16. Reductase enzymes and their role in carcinogen formation
Toxin - and carcinogenic-producing
enzymes have relatively low activity in bifidobacteria and lactobacilli compared to other more
harmful colonic microflora (Rowland, 1995). These alterations in bacterial enzymes can
interfere with the conversion of procarcinogens to its carcinogenic form and thus reduce cancer
risk. For example, Hidaka et al. (1986) fed rats a diet supplemented with tyrosine and
tryptophan as precursors to phenolic products. Fructooligosaccharides were administered at 0.4
to 10% by weight in the diet. Results indicated p-cresol levels were reduced in the fecal
material. Buddington et al. (1996) further noted significantly reduced nitroreductase
activity while using 4 g/day of FOS. In addition, the study showed reductive enzymes I- glucuronidase and glycoholic acid hydroxylate were decreased 75% and 90%, respectively. B-glucuronidase has implications in carcinogenesis through the release of aglycones from glycosides, while glycoholic acid hydroxylate is involved with the production of secondary bile acids, potentially linking it to the increased risk of cancer associated with high-fat diets (Buddington et a1., 1996). Rowland and others (1998) also demonstrated decreased ammonia concentration and B-glucoronidase activity in cecal contents in the presence of bifidobacteria, inulin, or both. As noted in Table 6, such components are known contributors to carcinogenesis of the colon in experimental animal models.
A change in the colonic microflora could also exert an anticarcinogenic effect, as bifidobacteria may actually bind carcinogens and physically remove them through the feces (Tomomatsu, 1994).
|Enzyme Activity||Metabolic Product||Toxicity|
|Urease||Ammonia||Liver toxin, carcinogen|
|Nitrate reductase||Hormonal substances||Cancer promoters|
|Nitrification||Secondary amines||Carcinogens/liver toxins|
|Glycoholic acid hydroxylase||Secondary bile acids||Carcinogens/colon cancer promoters|
Table 6: Metabolic products formed via enzymatic activity of colonic microflora
The hypothesis that cancer risk is affected through modulation of the gut microflora is supported in other ways. Consumption of Lactobacillus caseii and L. acidophilus was shown to reduce mutagenicity of urine and feces associated with the ingestion of carcinogens in cooked meat (Lidbeck et a1., 1992). Mizutani and Mitsuoka (1980), Hashimoto (1985), and Mizota and others (1987) noted that reducing or inhibiting the growth of certain pathogenic and putrefactive bacteria reduced the amount of N-nitroso compounds, phenolic products of tyrosine and tryptophan, metabolites of biliary steroids, and other potential carcinogens in the colon. In addition, Rowland and Grasso (1975) identified biidobaderia and lactobacilli as effective in reducing the conversion of secondary amines and nitrite to nitrosamine.
Asano and coworkers (1986) further showed L. cased inhibited the growth and metastasis of a transplantable bladder tumor cell line. Additionally, a study by Fujiwara and others (1990) showed a significant anti-cancer effect on BALB/C male mice (6 wks on day 0, 16/group) inoculated intraperitonially with Meth A fibrosarcoma (1.0E+05/mouse) on day 0 and treated with intraperitoneal injections of lactic acid bacteria (0.1 treatment) on days 0, 2, 4, 6, and 8.
It is possible that lactic acid producing bacteria might protect against cancer by preventing DNA damage and mutations, which are considered early events in carcinogenesis in cell cultures or in animals. Pool-zobel and others (1993b) demonstrated that several species of Lactobacillus inhibited the induction of mutations in Salmonella typhimurium by 60-85 percent.
A related study also provided evidence that administration of lactobacilli can decrease DNA damage induced by N-methyI-N-nitro-N-nitrosoguanidine (MNNG) in gastric and colonic mucosa in rats tpool-zobel et a1., 1993a).
Antitumoral immunity may also be increased by increasing the gut-associated lymphoid tissue (GALT) by inulin intake (Pierre et al., 1997), Figure 17.
Figure 17: Colon tumor suppression and GALE fluency Pierre et al. 1997
A study by Perdigon and coworkers (1998) utilizing BALB/c mice investigated the effects of yogurt, containing stock cultures of L. delbrueckii subsp. bulgarians CRL 423 and S.
salivation subsp. thermophilus CRL 412, on the inhibition of 1,2-dimethylhydrazine (died)- induced colon tumors. Results showed 70% of the control group ingesting a conventional diet and no yogurt developed colon tumors, while tumor growth was inhibited in the yogurt-eating group. The control group developed substantial influx of mononuclear cells into the lamia propria of the large intestine with an increase in IgG-producing cells, a slight increase in the IgAsecreting cells and of CD8+ but not CD4+ T lymphocytes. Further, the control group had a higher level of B-glucuronidase activity in the intestinal fluid and leucocytosis with neutophilia in the blood. The inflammatory immune response was reduced in the test group, with an increase in the IgA secreting cells (but not IgG) and no significant increase in either CD8+ or CD4+ T lymphocytes. The authors suggested one of the mechanisms by which the yogurt exerted antitumor activity was through its immunomodulator activity, which reduced the inflammatory immune response, a characteristic that was markedly increased when the carcinogen was administered.
lnulin added to animal diets has resulted in reductions in the number of aberrant crypt foci (ACF) (Reddy et al., 1997). Aberrant crypt foci are recognized as early preneoplastic lesions in the colon and as such, are considered predictive of eventual tumor incidence. Koo and Rao (1991) showed that oral Administration of indigenous bisdobacteha and the incorporation of a 5% inulin-fraction in the diet of CFI mice significance reduced the incidence of aberrant crypts and foci in the process of 1,2-dimethylhydrazine-induced colonic carcinogenesis. The aberrance also appeared to be confined to the more distal end of the colon in the animals fed the bifidogenic diet. Since Reddy and Rivenson (1993) have provided direct evidence of the effect of Bifdobacterium longum in preventing induction of colon, liver and mammary tumors in rats that were exposed to a common dietary mutagen, continuing study of the effects of prebiotics and/or probiotics on early pre-cancerous lesions or cancer initiation and growth seems justified.
Results involving two recent rat studies using dietary inulin show pronounced inhibitory effects on the development of azoxymethane (AOM) and dimethyl-hydrazine dihydrochloride (did) induced pre-neoplastic lesions, Figure 18. Verghese and others (1998), while working with Fisher 344 male rats, showed that a diet containing 10% inulin (DP ± 5; avg. DP 23 units) caused a 400% increase in cecal weights and a decrease in cecal pH from 6.04 to 3.74 as compared to controls. In addition, the inulin group showed over 50% reduction of azoxymethane (AOM) and dimethyl-hydrazine dihydrochloride (DMH) induced preneoplastic aberrant crypt foci (ACF) as compared to the control group, Figure 18. Reddy et at. (1997) found that both 10% oligofructose (avg. DP 4.5) and 10% inulin (avg. DP 25) added to a control diet at the expense of starch and fed to male weaning rats for 12 weeks resulted in fewer aberrant crypt foci per colon than control rats. The number of aberrant crypt foci was inhibited to a greater degree in rats fed long-chain inulin than in those fed oligofructose, Figure 18. However, others suggest that actual tumor growth may be more affected by oligofructose than inulin (Taper et al., 1997).
Figure 18. Effect of dietary inulin on carcinogen-induced ACF formation in rats
In another rat study involving AOM-induced aberrant crypt foci, Rowland et at. (1998), studied the effects of the consumption of Bifdobacterium longum anchor a 5% weight/weight inulin diet (avg. DP 22 units), Figure 19. The combined administration of both bifidobacterium and inulin resulted in 80% inhibition of aberrant crypt foci (ACF) which was more potent than administration of the two separately. The combined Administration also significantly decreased the incidence of large aberrant crypt foci (>4 aberrant crypts per focus) by 59%. Thus, an additive or synergistic relationship between inulin or oligofructose acting as prebiotics and added probiotics is supported in this studynand the work of others (Gllaher and Khil,1999).
Figure 19: AOM-induced ACF reduction with 5% inulin intake, Rowland et al., 1998
Work has also been completed to suggest that oligosaccharides have a role in reducing actual tumor cellinitiation and growth (Taper and Roberfroid, 1999). Since both decreased numbers of tumors and numbers of rats with tumors were detected following administration of methylnitrosourea to induce mammary tumors in rats, an antipromoting or antiprogressing effect was propose which requires confirmation in a larger study. In contrast, Menanteau and others (1998) have shown that diets containing resistant starch and oligofructose (avg. DP 4) were associated with reduce numbers of precancerouslesions in rats but had no efect on the later stages of carcinogenisis.
Work by Taper and others (1997) demonstrated the effects on tumor growth when 15% inulin was added to a basal diet and fed to mice that were transplanted with two tumor lines (EMT6, a mamary carcinoma,; and TLT, transplantable liver tumor). Results indicated the solid TLT tumor grew more slowly in mice fed inulin than in those fed basal diets alone. Likewise, mice fed 15% inulin also demonstrated inhibited EMT tumor growth compared to control mice. The authors proposed several mechanisms. They included the active fermentation by colonic bacteria, selective promotion of bifidobacteria growth, and alteration of colonic microflora, which could inhibit the number, and growth of tumors. Also, since tumor cell proliferation may be dependent on the availability of glucose and insulin levels (Basserga, 1995; Cay et a1., 1992; Giovanucci, 1995), and endogenous fatty acid synthesis (Kuhajda et a1., 1994), dietary oligosaccharides could exhibit an inhibitory effect by reducing these factors.
Collectively, these findings are indication that both probiotics (bifdobacteria) and prebiotics (oligosaccharides) might stem carcinogenic activity. Differences in initial colonic microflora populations, diet, age or sex of the rats, species or strain of the probiotic, number of viable organisms reaching the colon, and initial body weight at time of introduction of the carcinogen are all critical factors to consider when determining the effectiveness of either the probiotic or prebiotic (Gallaher et a1., 1996).
Human studies to investigate the effect of inulin and oligo|uctose on cancer risk are limited. Bouhnik and others (1996) found that 12.5 g/day FOS fed to 20 healthy volunteers in two week periods resulted in increased colonic bifidobacteria but there were no beneficial changes in factors that are potentially involved in the pathogenesis of colon cancer. In this study, fecal total Anaerobes, pH, enzymatic activities for azoreductase, B-glucoronidase, and nitroreductase, and the concentrations of bile acids were unaffected. However, under unique conditions, Vanurikhina et at. (1997) have been able to demonstrate a possible relationship between inulin and cancer risk. This study involved 25 people exposed to radiation as a result of the Chemobyl accident in 1986. Patients who ingested 10 g/day inulin for 2 months had reduced frequency of metaphases with chromosomal aberrations due to decreased pair fragments and translocations. In these exposed patients, inulin was associated with an expressed antimutagenous effect.
Based on the available research data with in/in-type fiuctals and originating from various types of animals models, it was concluded as part of the European Commission-funded ENDO project that these compounds consistently demonstrate a reduced risk in experimentally induced carcinogenesis processes (van Loo, et a1., 1999). The data further support the investment for performing human nutrition studies.
V. (b). Diabetes mellitus. Diabetes is the fourth leading cause of death by diseases in the U. S.
Nearly 16 million people have diabetes, 8 million do not know they have the disease yet and the U. S. has approximately 800,000 new cases per year (ADA. 1997). The number of new cases is expected to increase more than 33% in the next five years alone (Gallup, 1998). The chonic complications of the disease are many including macrovascular diseases such as hypertension, CVD, stroke, and peripheral vascular disease (room, 1997). Further, diabetes is the leading cause of new kidney disease cases and blindness (Campbell, 1997), and is responsible for more than half of nontraumatic lower limb amputations, due to nerve damage and severe infection (Kroom, 1997).
As a consequence of increasing incidence of this disease, people have begun to change their dietary habits, decreasing the glycemic index of foods they eat and supplementing their diet with active agents that can have influence on blood glucose and insulin levels. Foods containing fructans have had a long history for such use.
One of the earliest recorded uses of plants high in inulin as a hypoglycemic agent was by the Greek physician, Theophrastus, who used the dandelion plant (Taraxacum officinalis) for this purpose (Bolyard, 1981). The dandelion is also used by various cultures in Eurasia to balance sugar metabolism (Morton, 1981). In North America elecampane (Inula helenium) has been used lower blood sugar while the North American Squamish, Kwakwaka'waka, Nuu-chahnulth and Salish tribes of the Pacific Northwest use camps lily (Camassia quamash) as a sugar replacement poster & Duke, 1990.
The first reported attempt to study the fate of inulin in man was by Kulz (1874) who investigated its metabolism in diabetic subjects. In this century Root and Baker (1925) used inulin-containing Jerusalem artichokes in the diets for diabetic patients. When artichokes were added to the diet glycosuria was not increased if it was already present, nor was glycosuria detected if it had been previously absent. When Jerusalem artichokes were substituted for other carbohydrate-rich foods, glycosuria was reduced. Feeding of Jerusalem artichokes resulted in increased blood sugar but it was less than when an equivalent amount of fructose was fed. These findings offered some promise for the practical use of inulin containing foods in diabetic diets.
In more recent years, others also have suggested that inulin-containing food products may be beneficial to persons with diabetic disease due to effects on reducing glucose uptake and thereby reducing postprandial hyperglycemia (Kim & Shin, 1996). Yamashita and others (1984) fed 8 grams of fructooligosaccharide (Neosugar) for 14 days to 18 diabetic subjects. By the end of the study the diabetic subjects experienced 15 mddL decline in fasting blood glucose levels while control subjects showed no change. The implications from this study suggest that inulin-containing products may be useful carbohydrate substitute in diabetic diets. A more recent study, however, revealed that feeding 15 g/d of FOS for 20 days to 20 men and women with non-insulin dependent diabetes (NIDDM) did not favorably affect either serum glucose or lipid concentrations (Alles et a1., 1999).
In eight healthy human subjects, Rumessen and others (1990) also examined the effects of sultans from Jerusalem artichoke on blood responses. After a 20 gram load, these subjects demonstrated a lower glycemic response and insulin peak than when lactose was fed but a glucose response was experienced, nonetheless. The short-term nature of this study hinted that further long-term studies would be needed to further assess the physiological and nutritional benefits of using inulin products in both healthy and diabetic persons.
In 1996, Loo and others worked with 12 healthy male subjects in a double-blind crossover study. In separate four-week periods either 20 grams of fructooligosaccharide or sucrose were included in the diets. Results indicated that fasting levels of plasma glucose and insulin did not differ significantly between the periods. However, productions of short chain fatty acids were noted which could have an effect on liver glucose production. Further studies of the role of short chain fatty adds in regulating hepatic glucose and lipid metabolism were encouraged.
The health benefits of including oligosaccharides in diet may go beyond a direct effect on serum glucose or insulin levels. Some researchers suggest that magnesium deficiency increases the risk for both diabetes and myocardial infarction. Since fructooligosaccharides help to increase magnesium absorption (Ohta Baba et al., 1994; Ohta et al., 1995) it might be helpful in decreasing the risk of both of these diseases.
V. (c). Heart Disease. One of the main health concerns of the consumer is the risk of concurring cardiovascular diseases (CVD). This type of disease remains the major cause of untimely morbidity and mortality in the Western civilized world. More than 60 million Americans are diagnosed with some form of the disease (Sloan 1999), Today, twenty percent (or 10 million) of the children (<19 yrs.) are clinically obese. In addition, 27.4 million children under the age 19 have high cholesterol and 2.2 million have high blood pressure (American Heart Association, 1997). High blood pressure is a condition so common in the adult population that one in five Americans have it Kaplan, 1985). Currently, 96 million adults have cholesterol levels over 200 g/dL; 37.8 million have levels of 240 mg/dL or above (AHA, 1997). By 2005, the incidence of high cholesterol is expected to increase 15% overall and 33% Among 50-64 year olds (Gallup, 1998). Due to continuing education, nearly two-thirds (64%) of all adults in the U.S. are now aware that some of the cholesterol in their body is good and some is bad. Furthermore, twenty-five percent of those having their cholesterol checked are aware of their HDL/LDL ratio (Gallup, 1998). Therefore, it is not surprising that the possibility of exploiting the diet to reduce the risk of CVD is gaining ever-increasing interest.
While consumers have continued to have concern about these issues, only a few dietary ingredients have been shown scientifically to play a role in helping with such issues. A fairly recent development is the use of prebiotic food ingredients, such as inulin on the possible dietary factor for lowering serum blood lipids relevant for CVD.
As noted in the earlier discussion on the effect of inulin and oligofructose on lipid metabolism, a definitive role in alterations in serum lipid levels seems to be dependent on preexisting lipid levels, individual variations, and duration of administration of inulin and/or oligofructose, and previous level of dietary fat intake. If serum total cholesterol and LDL cholesterol can be reduced without also reducing HDL-cholesterol, there will be a positive impact on long term risk for heart disease, especially in those who are at risk due to high serum lipid levels. Further, as noted in the Nutrition metabolism/vitamin section bifidobacteria also produce B-complex vitamins (B1, B2, B6, nicotinic acid, B12 and folic acid). These vitamins are necessary to help metabolize and eliminate homocysteine, a molecule produced by the breakdown of the amino acid methionine.
Reduction in homocysteine levels is vital to a healthy cardiovascular system, as levels rise homocysteine damages cells and tissues of the arteries, interferes with the constriction and dilation of blood vessels, promotes blood clotting, and stimulates growth of arteriosclerotic plaques, which lead to heart disease (McCully, 1993). Homocysteine is abundant in animal protein and dairy products, and can rise to significant levels when there exists a deficiency of the B vitamins-B6, B12 and folic acid. In addition, normal aging and female hormones following menopause also increase homocysteine levels (Rimm, et al., 1998).
V. (d). Immune system. Systematic studies to fully assess the role of inulin and oligofructose on lymphocyte activity or other tests of immune function are needed. Part of the hypothesis that
inulin may play a role comes from work with yogurt as a bearer of lactic acid producing microbes (Hitchins & McDonough, 1989; Van de Water, Keen, & Gershwin, 1999). According to the hypothesis, ingestion of a lactobacillus culture may stimulate an immune response. Since lactic-acid producing bacteria can be stimulated when inulin is ingested, a similar immune response might be generated.
Of additional interest is the wide historic use of inulin-containing immunostimulating medicinal herbs. The most widely recognized of these herbs, is Echinacea angustfolia, containing about 6% inulin. inulin, the primary water-soluble polysaccharide of Echinacea, has significant stimulatory effects on the cellular immune system (Bauer & Wagner, 1991). Even though a number of other immunostimulatory and mild anti-inflammatory polysaccharides have been isolated from Echinacea specie (Rawls, 1996), inulin is the most notable of the Echinacea polysaccharides. The herb is one of the best-selling herbal medicines in the U.S., and is an important herbal drug in Europe as well bawls, 1996).
The alternative complement pathway (ACP) plays a central role in the immune response.
Finely deeded, insoluble gamma form inulin, but not more soluble alpha and beta types, has been shown to activate the ACP, leading to triggering of complement C3 receptors on the surface of macrophage (Cooper & Carter 1986a). When injected intraperitoneally in mice, the gamma form has been shown to elicit an anti-tumor effect (Cooper & Carter, 1986b). Native inulins, containing primarily alpha and beta type inulin molecules, have anti-complementary action, but are relatively low as compared to gamma form inulin (Cooper, 1995). Using keyhole limpet hemocyanin (KLH) as an immunogen in mice, Cooper and Steele (1988) showed that intrapentoneal injections of gamma inulin also increased secondary IgG responses (5-to 28 fold, p<0.001) and was determined to have vaccine adjutant action (Cooper, 1995). During its use as a vaccine adjutant, gamma inulin was shown to boost the lgG2a, lgG2b, and IgG3 subclasses several hundredfold, IgG1 tenfold, and IgM and IgA four - to sixfold. In addition, human interleukin-2 (IL-2) secretion was enhanced 7 - to 41 fold in response to gamma inulin plus tetanus toxoid in PBL cultures in vitro (Cooper, 1995).
Feeding inulin has also been demonstrated to impact the immune system. Kelly- Quagliana and others (1998) used B6C3F1 mice to examine the immunomodulating properties of inulin (avg. DP 22 units). By measuring natural killer cell activity in spleenocytes and quantifying phagocytosis by peritoneal lavage microphones, they determined that inulin fed mice had increased percentage of NK cells (p<0.0005) and/or an increased speed of macrophage response. Causey and others (1998b) provided further evidence that inulin, particularly long chain inulin molecules (average DP 22 units), stimulate the human immune system by binding to specific lectin-like receptors on leukocytes. Data indicate that long chain inulin molecules stimulate macrophage proliferation without a concomitant rise in the inflammatory marker leukotriene B4 (LT-B4), Figures 20 and 21. The long chain inulin also did not stimulate interleukin - 1a (IL-1a) production at 25, 50 or 100 ug/mL. It was suggested that higher concentrations of inulin may enhance production of this cytokine.
Figure 20: Human macrophage growth from carbohydrate treatment, Causey et al. 1998
No arabinoxylan response
Figure 21: LT-B4 secretion from carbohydrate treatment, from Causer et at, 1998
V. (e). Gastrointestinal Health (GI) Today, 70 million Americans suffer from digestive diseases or disorders, 15% on a daily basis DK, 1997). An even larger population, approximately 118 million, experience heart burn or are afflicted with gastroesophageal reflux disease (GERD) at least once a month. While smaller in number, suffers of other gastrointestinal disorders remain relatively large such as peptic ulcers (5 million), irritable bowel syndrome (5 million), gastritis (2.7 million), nonulcer dyspepsia (5.8 million), and constipation (4.4 million). Even potentially more alarming is the projected 35% increase in the number of adults age 50-64 to be afflicted with digestive problems in the next five years and its potential impact on the health care system (Gallup, 1998).
Due to these afflictions, Americans use gastrointestinal relief systems at an astounding rate. It is estimated that 90 million people use antacids or other stomach relief medicines (Euromonitor, 1998). Next to headaches, stomach problems are one of the most self-treated ailments in the U.S (American Pharmaceutical Assn., 1997). Further, one of the strongest health links for herbal and nutraceutical medicines is the ability to prevent and treat digestive problems. Related to this need to self-treat their digestive ailments and maintain proper GI health is a growing awareness of various nutraceutical ingredients having GI health related effects.
Fructan-containing plants have been used for centuries to promote gastrointestinal health and treat problems of the GI tract. Theophrastus notd one of the earlies recorded uses of plants high in inulin to treat stomach and gastrointestinal aflictions. He used the dandelion (Taraxacum officinalis) as an effective laxative and diuretic (Bolyard, 1981). The Kiwis New Zealand Aborigines attribute laxative properties to treat chronic constipation to Taraxacum magellanicum (Brooker et al., 1987). Hippocrates, the father of medicine, used elecampane (Inula heleniumasparagus (Asparagus officinalis), as a diruetic and laxative (Potter,1907). However, the most common plant used historically for gastrointestinal amladies and urinary disturbances by ancient and medieval cultures was chicory root (Cichorium intybus). In the first dated cook book, circa 1475 A.D., Bartolomeo de Sacchi de Padina established cooked chicory and broth would settle and cool a thoroughly warmed and lax stomach (Piadenda, 1475). In 1597, Gerard noted that chicory be something bitter that do also cleanse and open (Gerard, 1597). North African aborigines know Cicorium intybus as seris, shikouria, and didijouldjoulan and use the roots of the plants as stomachic, diuretic, laxative, and to stimulate bile secretion (Boulos, 1983). The El Salvadoran medicos use chicory for its laxative and diuretic properties (Morton, 1981). The French and German cultures refer to chicory as barb de capuchin, bois de cord, verfluchte junfer and blausamenwirbel and use the roots as a tonic, diuretic and laxative (Caius, 1986).
Various species of Inula roots have been widely used in Asia for promoting gastrointestinal and urinary tract health. Of these, I. Helenium and I. Britannica are used in China to control diarrhea and dysentary as well as balance spleen, stomach, and large intestinal problems (Hsu, 1986). lnula racemosa is also used in the Kashmir as a diuretic (Kurup et al.,
Campbell et al. (1997) suggest that gastrointestinal health can be improved by feeding oligosaccharides because of their effect on short chain fatty acid production, lowering pH, and increasing bifidobacteria. However, since oligosaccharides reach the large intestine largely intact, the possibilities exist that gastrointestinal discomfort will be experienced and might be a factor with which to contend (Rumessen et al., 1990). As an example, rats have developed diarrhea after starting FOS feeding which persisted for two or three weeks (Tokunaga et al., 1986). The FOS levels used would be comparable to more than 10 g per kg of body weight. Saunders and Wiggins (1981) have indicated the human colon is capable of removing appreciable amounts of single doses of poorly absorbed carbohydrates. When capacity is exceeded, however, increased diarrhea can result. Some human studies have shown that intestinal discomfort, particularly flatulence, is present (Davidson & Maki, 1999; Pedersen et al.
1997) while others show no gastrointestinal side effects up to 20 g/day of short-chain FOS, especially when dosages are increased gradually (Molis et a1., 1996). However, longer more polydispersed, inulin molecules (DP 2 to 60; avg. 10 units) have been shown to be more well tolerated, with only mild discomfort at consumption levels of about 40 g-day (Kleeseen et at.
1997). Refer to the safety and tolerance section for further details. Because inulin and FOS have somewhat laxative effects, they might be helpful in reducing constipation with only mild discomfort (Hidaka et al., 1991; Kleessen et a1., 1997; Tominaga 1999).
It has been proposed that irritable bowel syndrome is a common gastrointestinal disorder that also may be aided by supplementation with inulin due to its effects on bifidobacteria numbers. Further, Scheppach (1994;1998) has suggested that butyrate, one of inulin's fermentation products, could potentially be an important variable in ulcerative colitis and malabsorption disorders. Hunter and others (1999) found that supplementing 6 g of oligofructose (2 g three times daily) was insufficient for achieving differences in fecal weight, pH, whole-gut transit time, and fasting breath hydrogen concentrations in individuals who were suffering from irritable bowel syndrome. The dose level used in the study may have been too low to achieve differences but higher levels of this short chain fructan may also prove difficult to use with this population due to fears of provoking undesirable responses such as diarrhea, pain or flatulence. Further, oligofructose as a short chain fructan is readily fermented in the proximal colon, while ulcerative colitis and inflammatory bowel disease are more pronounced in the distal colon. Thus it is likely important to have butyrate formed in the distal colon rather than the proximal colon. As long chain inulin molecules are generally fermented more slowly they are capable of reaching later stages of the colon, likely providing more effective means of meeting a desired response with less undesirable responses such as diarrhea, pain or flatulence (see sections on safety and tolerance and Figure 12 regarding SCFA production and intestinal tolerance).
V. (f). Dental Health. Use of inulin/FOS as a replacement for other carbohydrates may have a role in dental health. Inulin and oligofructose have synergistic effects when combined with sweetening agents aspartame and acesulfame-potassium. The lingering high-intensity aftertaste of several high-intensity sweeteners, particularly the two mentioned, can be corrected towards a more natural sweetness profile, improving the mouthfeel and use for oral products, such as chewing gums and hard confections. Further, inulin and oligofructose provide improved elasticity and prevent drying of these oral confections. Inulin and oligofructose are acariogenic. Using in vitro experiments with dental plaque, researchers have shown that low molecular weight fructans (DP<5) may serve as substrates to oral microorganisms such as certain strains of streptococci (Nilsson et al., 1988). However, the in vitro acid production rate was low compared to glucose. Telemetry tests have shown that inulins used as the only bulking components in chewing gum produced no decrease in the oral pH under the critical limit of 5.7 (De Soete, 2000).
V. (g). Skeletal Health and Menopausal Support. In order to have a healthy skeletal system calcium is a vital element. Bones are made up of primarily calcium phosphate and the lack of adequate calcium at all stages of life can have devastating consequences, making the skeletal system more fragile and prone to tinctures and disabling the individual. Low calcium intake and potentially vitamin D (a cofactor for gastrointestinal absorption of calcium) is of particular concern with individuals, such as children and teenagers, with growing skeletal systems, pregnant and lactating women, individuals on corticosteroids and postmenopausal women, In the case of menopausal women, the result of inadequate calcium can lead to osteoporosis.
Osteoporosis is a common disease of the skeleton related, particularly to hormonal changes in women at menopause and lack of adequate calcium uptake and utilization. Osteoporosis, literally means porous bone and results from gradual loss of bone mass, which leads to fragility fractures in bone. According, to the National Osteoporosis Foundation (NOF), osteoporosis affects one in three women after menopause. Ten million women already have osteoporosis and 18 million more have low bone mass. In Addition, 5 million men also have the disease. The NOF also has determined that osteoporosis is responsible for 1.5 million fractures annually, especially in the spine, hip and wrist Moreover, 50 percent of women and 17 percent of men have osteoporosis fractures by age 80. While many of these fractures cause serious pain and may limit function and activities, hip fractures are particularly dangerous. Within one year of a person's hip fracture, 12-20 percent die, and 50 percent of survivors have permanent disability. Osteoporosis is responsible for $13 billion in direct medical costs per year in the U. S.
Osteoporosis can be diagnosed by a medical history, physical signs such as height loss or dowagers hump, and laboratory tests and imaging techniques, such as dual-energy densitometry. Several factors predispose individuals to osteoporosis such as: strong family history, menopause, and corticosteroid use, low calcium intake, cigarette smoking, alcohol abuse, little exposure to sunlight and lack of exercise. However, the two most common causes in the etiology of osteoporosis are low calcium intake and estrogen. Calcium is important for many reasons at all stages of life, and the loss of estrogen at menopause is also associated with accelerated bone loss.
Osteoporosis mainly affects women because they reach a lower peak bone mass than men, reaching a peak in the late 20's, and the rate at which bone losses density is steeper for women when they reach menopause and lose estrogen. Thus, enhanced calcium uptake and bioavailability and estrogen maintenance are key elements in the fight against osteoporosis.
As the human body only absorbs a inaction of dietary calcium (25 to 50%), food manufacturers have developed calcium-enriched food products. However, in order to increase calcium uptake by 50%, the calcium content of food must be increased by an equal percentage.
Use of inulin, particularly in combination with other nutraceutical ingredients such as soy isoflavones may play an important role in prevention of osteoporosis by increasing total dietary calcium absorption, increasing recycling of estrogen-like componds (reducing the rate of bone loss), and increasing bone density. Inulin and oligofructose have been shown in human studies to enhance dietary calcium absorption, maintain healthy calcium balance and provide means to improve bone density (van den Heuvel et al., 1999; Coudray et al., 1997; Ellegard et al., 1997). Further, the positive growth-promoting effects inulin has on probiotic bacteria populations could potentially enhance estrogen re-cycling which can also affect bone health (Chaitow & Trenev, 1990). As summarized by Chaitow and Trenev, sixty percent of the circulating female hormones such as estrogen are excreted via bile into the GI tract. Under normal healthy conditions, the hormones are converted by bacterial enzymes such as sulphate catalyze to a recycled form which is mostly resorbed into the bloodstream and converted to a biologically active form.
However, under conditions such as those resulting from broad-spectrum antibiotic use, improper diet and stress, levels probiotic bacteria can substantially decrease potentially leading to lower estrogen recycled in to the bloodstream. If inulin as a prebiotic, can boost the appropriate bacterial populations, the recycling effect might be maintained.
As mentioned, calcium absorption and bone density can be improved through human consumption of inulin. The use of inulin, particularly when combined with adequate calcium and vitamin D intake at all ages, regular exercise (against gravity), and hormone replacement therapy (postmenopausal women) can play an important role in the prevention of osteoporosis.
In addition, certain medicines can also be used when appropriate to slow down bone loss, such as bisphosphonates (Fosamax, Didronel, and others) and calcitonin (Miacalcin spray and others).
V. (h). Opportunistic infections (Urinary tract health and Candidiasis). Infections of the urinary tract (UTIs) are common, only respiratory infections occur more often. The National Institute of Health estimates that UTIs account for about 9.6 million doctor visits per year (NIH, 1999). Women are especially prone to UTIS for reasons that are poorly understood, but believed to be partially related to their anatomy. Children also are prone to UTI infections. Three percent of girls and one percent of boys have had a UTI by the age of 11 (NIH, 1997). The most common organism responsible for UTIs is E. coli (85%) that is found in the colon and rectal areas. However, other types of colon: microflora also involved are Staphylococcus saprophyticus, (as high as 10%), Klebsiella (5%) and occasionally Proteus mirabilis or Enterococcus faecalis, Enterobacter sp. and Pseudomonas sp. (Graber and Martinez-Bianchi, 1995). Probiotics, particularly Lactobacillus acidophilus strains, have been used with some success in helping to maintain a healthy balance of colonic microflora (Elmer et al., 1996, Kageyama et al., 1984; Pochart et al., 1992). In particular these bacteria are used as aids in treating and preventing pathogenic microorganism overgrowth, especially following periods of antibiotic therapy, or used with individuals having suppressed immune systems or those people on immunosuppressive drugs (Elmer et al., 1996). In addition, dietary habits can also alter normally healthy gut microflora, such as the overuse of alcohol, tobacco, coffee or caffeinated beverages (Lee, 1988; Gates, 1996). Overuse of these antagonists and particularly therapeutic use of broad-based antibiotics can create situations for opportunistic yeast overgrowth, cause of thrush in breasted infants, and other health problems related to candidiasis.
As mentioned in the bifdogenic section, probiotics resist opportunistic pathogen colonization by aggressively competing for attachment sites on the colonic epithelial wall and by producing pathogen antagonistic agents; i.e., acetic, lactic acids benzoic acid, hydrogen peroxide and several natural antibiotic substances. However, since probiotic effects may be transient (Bounik et a1., 1992), use of prebiotics such as inulin may provide another means to selectively modify colonic microflora populations, and establish a healthy colonic balance. Relative to lactic acid producing bacteria (L. acidophilus), opportunistic pathogenic microorganisms such as Candida (yeast infections), clostridia (Cl. difficile antibiotic associated diarrhea) and E. coli, and other members of the Enterobacteriaceae family (urinary tract infections), Figure 22 (Cagey, et al.
2000) are intolerant of low pH levels (5.0 and 4.5) (Wang and Gibson, 1993, camera et at. 1990, Borriello, 1990, Hopkins et al., 1997); and normal pathogenic gut microorganisms do not have highly active intracellular 2,1,B-d-fructan-fructohydrolase enzymes Hudson et al., 1993; McKellar et al., 1993).
Figure.22. Effect of 20 g/d full consumption on Enterobacteriaceae.
Further, only five of the clinically significant yeast species can use inulin to any extent as a growth substrate (Bamett et a1., 1990). As consequence, the overpower of opportunistic pathogenic microorganisms may be selectively reduced and maintained with the use of probiotics and selective prebiotic agents, like inulin However, selective prebiotic agents function effectively only when there are populations of probiotic bacteria present to nourish. In certain situations, where yeasts have overgrown and they are the predominate species, such as following intense antibiotic therapy, it may also be necessary to get control of the overgrowth situation before working towards microflora modification, and further prevention. In situations where yeasts have overgrown, and control has been reestablished, introduction of a specific probiotic (to repopulate the colonic flora) and a selective prebiotic to selectively nourish the probiotic may be used to prevent reoccurrence. Thus, the primary application for inulin in opporrtunstic disorders is likely prevention of overgrowth rather than its therapeutical use, its therapeutic use being dependent on several variables, such as magnitude of the overgrowth condition, and specific strain(s) of organism(s) involved.
In addition to yeast infections, opportunistic E. coli overgrowth can have substantial clinical significance. Consumption of inulin, by mechanisms defined in the bifidogenic section, has been shown to significantly reduce concentrations of these bacteria, minimizing the potential for their overgrowth into other areas of the body.
Inulin consumption in itself should not be viewed as a single dietary component or single mechanism disease prevention. The best mechanism for prevention of UTIs is likely a systems approach, using good common sense, and hygiene, diet and other active nutritional components. Dietary recommendations include drinking plenty of fluids, especially cranberry juice, drinking at least one 8-oz. glass of quality water every hour. Individuals should include celery, parsley, and watermelon in the diet, as these foods are natural diuretics and urinary cleansers. Further, people should avoid alcohol, caffeine, chocolate, as these dietary components have detrimental effects on probiotic bacteria, 1999; Giber and Martinez-Bianchi, 1995).
VI. FUNCTIONAL CHARACTERISTICS AND FOOD APPLICATIONS
Inulin possesses unique physical and physiological characteristics making it widely useful for adding texture in food applications. For example, when inulin replaced corn syrups in reduced fat ice cream formulations a chewier texture was created. However, ice crystal formation was reduced when 50% of the corn syrup was replaced with inulin during thermally abusive storage conditions (Schaller-Povolny & Smith, 1999). In consumer tests, plain unsweetened yogurt containing inulin was preferred over samples without inulin. Yogurt with inulin was identified as being creamier in appearance, having a less chalky and more creamy texture, and was sweeter with a less sour/fermented taste and aftertaste (Spiegel et al., 1994).
Yogurt made with 10% inulin with a DP of 12-16 was found to increase firmness and decrease synthesis compared to yogurt made with shorter chained inulin (DP 5-8) and controls with no inulin (Terry et a1., 1999). Due to the unique functional properties inulin has to manage water effectively, affect rheology and improve texture in foods and act synergistically with high water binding hydrocolloids has allowed inulin to be used across all food product application areas, particularly in low and no fat and low and no sugar systems.
Purified, analytical-grade inulin occurs as spherical crystals with radial striation. Its average molecular weight is between 5,600 and 6,300 fluctuations depending on the degree of polymerization of the molecules used in the measurement. However, refined native inulin powder from chicory is white, amorphous, and slightly hygroscopic; has a specific gravity of about 1.35 and an average molecular weight of about 1,600. It is neutral in odor and taste. Commercial inulin contributes a marginally sweet taste due to a small amount of naturally occurring mono-and disaccharides.
Inulin is soluble in water with the solubility dependent on the temperature of the water, degree of polymerization, distribution of the molecular chains, degree of molecular branching and how the molecule is processed. Typically, native chicory inulin is soluble to about 60 g/L. at 10oC, while at 90oC it is soluble to about 330 g/L. Under normal conditions native chicory inulin is dispersible in water but may have a tendency to clump during hydration due to its hygroscopic character. Dispersability may be improved either through mixing with sugar and/or starch or by instituting the final product. Native chicory inulin has a water binding capacity of about 1:1.5.
Native chicory inulin has a unique ability to add rheological and textural properties to food due to its ability to form discrete highly stable particle gels. Inulin gel characteristics are dependent on a number of factors including inulin solids concentration, which becomes more viscous and fat-like as inulin solids are increased, In addition to concentration, inulin chain length distribution also affects gel characteristics. Higher degrees of polymerization (long chain frictions) lower the inulin level required to form a gel. Increasing amounts of monomer and dozer content decrease viscosity, inulin gels are very creamy and fat-like, and as such can be used in fat reduction and fat-replacer systems.
VII. SAFETY AND TOLERANCE
Estimates of current daily inulin consumption from various natural foods range from 1 to 4 grams for Americans and up to 12 grams for Europeans (Marched 1993b), Historically, the dietary intake of inulin has been significantly higher than current-day consumption estimates, as stated previously in other sections. Estimates of inulin intake from consumption of these foods include approximately 25 to 32 grams of inulin per day by European populations substituting Jerusalem artichokes for potatoes and approximately 160 to 260 grams of inulin per day from inuling consumption by the Australian aborigines.
Human tolerance to inulin, as a class of compounds, is primarily dictated by chain length and dosage alumessen and Gudman-Hoyer, 1998). Abdominal symptoms, primarily gas and some abdominal discomfort, increased with increasing dose and decreasing chain length.
Osmotic diarrhea associated with ingestion of unavailable or unobservable oligosacchahides notably increases as the molecular weight of the molecule decreases and as such is the most significant factor in determining tolerance in humans (Nilsson & Bjorck, 1988; Tokunaga et al.,
1986). Therefore, human tolerance to long chain inulin (DP > 5; avg. DP 23) is greater than native chicory inulin (DP of 2 to greater than 60, modal DP 9 units) is greater than the tolerance of FOS (DP 3 to 7, average 4.8), which, in turn, is greater than the tolerance of shorter-chain FOS (DP 3 to 5, average 3.7). In both historic times and contemporary times, dietary exposure to the entire range of chain lengths comprising inulin has been orders of magnitude greater than exposure to any specific subset of hydrolyzed or shorter length inulin-type compounds (fructooligosaccharides). Consequently, human and animal gut microflora utilizing these non-digestible carbohydrates have evolved active inulinase enzymes.
Similar to other dietary fibers, human tolerance to inulin has been demonstrated to be greater when inulin is part of the regular diet, spread out over the course of the day, as opposed to a bolus dose. Absolonne and others (1995) observed an increase in tolerance to FOS (DP 3 to 7) when the initial, single dose was split into two doses administered in the morning and afternoon, respectively. Under those conditions, the maximum daily dose that did not cause reactions was 27 to 31 g for men and 33 to 37 g for women. They determined the lowest laxative dose (not causing liquid stools) to be 41 g for men and 40 g for women.
Shorter chain FOS (DP 3 to 5), which caused adverse effects such as diarrhea when initially consumed in large amounts, were more readily tolerated with continued consumption (Oku, 1986). The maximum dose to not cause diarrhea was approximately 21 to 24 g per day (Hate & Nakajima, 1985; Takahashi et al., 1986). However, lower doses of 10 to 15 g FOS (DP< 10; median DP=3) has resulted in intestinal rumbling and flatulence (Rumessen & Gudmand-Hoyer, 1998; Stone-Dorshow & Levitt, 1987). Lower doses of shorter chain FOS (DP 3 to 5) in the 3 day, are typically well-tolerated in healthy populations. A recent study by Tominaga (1999) involving 34 healthy female subjects 18-21 years of age ingesting 3 g/d FOS showed higher stool frequency for individuals having normal stool frequencies of <= 5 times/week than control groups. No significant difference was reported for individuals having stool frequency greater than 5 times/week when compared to the FOS treatment group. Moreover, stool condition (hardness and color) and mean transit time were unaffected by the FOS consumption.
Wilpart (1993) reported a rat study involving various indigestible dietary fibers, including inulin. They found that diarrhea incidence was higher with many polyols such as maltitol, mannitol, sorbitol or xylitol compared to most fructooligosaccharides. Wilpart reported adaptation to inulin took place within one week, resulting in no untoward effects. In a human clinical study, Kleessen and colleagues (1997) have shown that intakes up to 40 g per day of inulin produced no untoward effects, especially when divided over the course of a single day.
For those who reported milk to be their cause of gastrointestinal symptoms (pseudohypolactasia), a 25 g dose of FOS was found to cause significantly more symptoms than in a control group.
This 25 g level of intake may not initially be well tolerated by individuals who already experience gastrointestinal problems (Tend et al., 1999). Review of the clinical study data, indicates regular consumption of 40 to 70 grams of native chicory inulin DP 2 to 60; avg. DP 9) per day by healthy adults appears to result in no significant adverse effects, especially when the consumption is in divided doses over the course of the day. This estimated consumption range is further reinforced by observations in recent review articles, reporting consumption amounts up to 40 grams of inulin daily in various food preparations do not lead to any undesired side effects (Feldheim, 1993, as cited in Gruhn, 1994, Kleessen, 1997).
VII. (a). Legal and Regulatory Status. Inulin derived from various natural sources, such as chicory root, dahlia, and Jerusalem artichoke is legally classified as a food or natural food ingredient, and has non-additive status. In the United States, inulin has food ingredient status and is Generally Recognized as Safe (GRAS) referring to compounds having significant pre1958 human food use and meeting key elements of human safety, as defined by scientific experts. As stated in GRAS policy, inulin can be used without any significant restrictions for all intended food categories, unless the food is standardized and the standard does not permit its use. Canada also accepts inulin as a food ingredient without restriction on use level or the foods in which it can be used, provided there are not limitations on standard of identity for a specific food.
Inulin is classified as a food ingredient according to the European Directive 95/002 on Food Additives, and is excluded from additive status. All the European Union (EU) countries list inulin as having food ingredient (non-additive) status. Other countries giving inulin food ingredient status are Norway, Finland, Denmark, Ireland, United Kingdom, Switzerland, Israel, South Africa, Australia, New Zealand, and Japan. In addition to its food ingredient status, inulin is further considered as an agricultural product in Europe as part of the EC Treaty (Article 38, Annex II).
VII. (b). Nutritional labeling.
VII (b). 1. Ingredient declaration: In the United States, inulin must be declared following policy written in 21 CFR I 101.4 describing that ingredients declared shall be labeled by their common or usual name so as to accurately identify or describe the basic nature of the food or its ingredients. Acceptable declarations, as defined in GRAS documentation for inulin include, indium polyfructose, oligofructose, fructooligosaccharide (FOS), or natural extract of chicory root or other descriptor of their plant origin, when used in combination with any of the common chemical descriptors above. In countries other than the US, the terms dietary fiber, vegetable fiber, chicory root fiber may be used as single entities on the declarations but require review by each countries regulating agency.
VII. (b). 2. Dietary Fiber Status: Inulin and oligofructose are dietary fiber by their definition and their nutritional properties. In the United States, Canada, Australia, and some other countries that define dietary fiber by prescribing a specific Analytical method be used, such as an official AOAC-type, inulin and oligofructose cannot be labeled in their entirety on the nutritional or supplemental facts panel.
In Europe, according to the European Nutrition Labeling Directive 90/496, inulin and oligofructose can only be designated as being either carbohydrates or as dietary fiber. Inulin has been accepted as a food ingredient for labeling as dietary fiber in all the EU countries as well as
Norway, Finland, South Africa, Ireland, Switzerland, and Portugal. The United Kingdom, a
country requiring specific methods be used for dietary fiber labeling, accepts inulin and oligofructose as labeled dietary fiber basis the official AOAC method numbers 985.29 (total dietary fiber in foods enzymatic-gravimetric method) and 997.08 (fructans in food products, ion exchange chromatographic method).
VII. (b). 3. Caloric Value: In the United States, caloric values for specific food components are specified under 21 CFR ? 101.9, Nutritional labeling. In the United States inulin and oligofructose are classified as other carbohydrates for nutrition facts labeling and have a scientifically defined caloric value of approximately 1.5 kcal/gram. The Canadian government allows an energy value of 2 kcal/gram to be used on product labels. Caloric values in Europe are specified in the Nutrition Labeling Directive 90/496. Under this directive, dietary fiber having no specified caloric value, should be calculated at zero kcal/gram. In certain European countries (Italy, Switzerland, Sweden, and Norway) this principle applies, they use the zero value.
However, since nutritional research shows that the caloric value of inulin and oligofructose is not zero several countries have assigned a caloric value that more closely approaches the scientific evidence. For example, Belgium and The Netherlands use 1 kcal/g; Denmark, France, and Finland use 2 kcal/g; and Germany uses 1.5 kcal/g. In countries not having an assigned caloric value, the value of 1.5 kcal/g is generally used.
VII. (b). 4. Claims (types and current status)-General guidelines: Nutrition claims refer to claims that are made regarding the nutritional make-up of the product or ingredient and its (their) effects on the body such as nutrient content claims, comparative or relative claims, and structure/function claims. No reference can be made to the dietary fiber level associated with inulin in the US and Canada, due to current dietary fiber labeling issues. In Europe, the rules permitting the use of specific nutrition claims vary, but generally, fiber claims such as with added fiber, fiber-enriched, source of fiber, high in fiber, with fiber function are acceptable when dietary fiber labeling is approved.
Comparative claims refer to inulin acting as a sugar - and/or fat replacer, caloric reduction, and providing less, reduced, or more of something. Comparative claims are acceptable in the US, Canada and in most European countries, but can vary somewhat by country, Generally, claims such as, ''fat/sugar reduced, low in fat/sugar, x% fat/sugar free, no sugar added are acceptable and are referred to basis a reference food.
Structure function claims generally refer to the effect inulin has on the structure or function of the body. The claims, however, cannot suggest that the food is useful in the diagnosis, cure, treatment, prevention or mitigation of a disease or health related condition, which are health or drug claims. However, structure function claims may be used to describe non-disease states, (e.g. effects on aging, menopause, and bone care). Structure function claims are acceptable under DSHEA 21 CFR ? 101.93 in the US, but are not approved, currently in Canada. They are generally allowed in varying degrees in European countries. Bilidobacteriarelated claims may be made such as ''bifidogenic, stimulates natural besides flora, improves microflora balance/equilibrium, and prebiotic. Examples of structure/function claims in the US for inulin are: ''bifidogenic, improves microflora balance, helps maintain a healthy cholesterol level, helps promote urinary tract health, helps maintain cardiovascular function and a healthy circulatory system, helps maintain normal bowel function and aids with constipation, helps maintain regularity, helps promote the immune system, helps with mineral or calcium absorption, helps support the effects of menopause, helps promote bone health, helps prevent the effects of aging.
Health and medical claims refer to disease prevention and the treatment or cure of a specific disease, respectively. Neither of these types of claims can be made for inulin at this time.
Inulin-fructooligosaccharides (FOS) belong to the group of carbohydrates known as non-digestible oligosaccharides (NDO) and have a long history of human consumption. inulin has a number of dietary advantages, which are mainly involved in the promotion of bifidobacteria, as confirmed by in vitro and in vivo studies. inulin has all the characteristics and health benefits common to non-digestible polysaccharides (NDP) and resembles those attributed to dietary fiber.
However, inulin does not possess the typical physical effects of dietary fiber, such as dramatic viscosity-building, intense water holding, large increases in osmotic pressure and intestinal bulking effects. Several of the more pronounced health contributions of inulin arise from its ability to selectively stimulate in vivo in humans the growth of bacterial genera and species known as beneficial for health, such as Bifdobacteria (except B. bifidum) and Lactobacillus, at the expense of potential pathogenic microorganisms (Cl. perfringens. C. difficile, E. coli, and K. pneumoniae). Therefore, inulin is generally considered a prebiotic with a bifidogenic factor. In contrast to probiotics, prebiotics like inulin are not unduly affected by their environment, but rather have the advantage of inducing the selective growth of endogenous bacteria in their normal environment.
Positive effects on gut microflora blood glucose attenuation, lipid homeostasis, mineral bioavailability and nitrogen, immunomodulation effects, along with the ability to add texture and improve rheological characteristics and nutritional properties of foot allows inulin to be termed a 'physiologically functional food' or food ingredient, or more simply, a food with potential health-promoting effects.
Since interest in inulin as a functional food ingredient with health promoting properties has been more intense in recent years, further research needs to be completed to more fully elucidate the health implications of inulin consumption. Additional data to determine effective levels of intake for specific health purposes need to be obtained. Studies to determine differences in the physiological effects of short, medium and long chained FOS/inulins and their blends need to be conducted. Before US food companies more fully accept inulin-type fructans as ingredients, more work to further understand human intestinalsensitivity and tolerance is important. More studies with healthy populations and populations with acute and chronic disease states are also needed.
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