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Tools and Resources
Fructooligosaccharides (FOS)
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Active Forms
Structurally, FOS molecules consist of a glucose molecule with a number of fructose molecules attached in a chain-like manner. The most common fructooligosaccharides contain a chain of two, three, or four fructose molecules attached to the head glucose molecule. The abbreviations (G = glucose and F = fructose) and names of these corresponding FOS compounds are as follows: GF2 = 1-kestose, GF3 = nystose, and GF4 = 1F-b-fructofuranosylnystose. Other substances contain longer chains of fructose molecules, but the compounds containing 2,3, and 4 fructose units are the ones that occur most commonly in FOS products.
Absorption
Fructooligosaccharides are not digested or absorbed from the gastrointestinal tract of humans. Instead, they pass through the GI tract into the colon where they are used by bifidobacteria as a preferential source of food and energy.
Dietary Sources
Fructooligosaccharides occur naturally in a variety of foods such as bananas, Jerusalem artichoke, onions, garlic, chicory, wheat, and barley. However, therapeutic amounts cannot be obtained from these dietary sources.
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| Dosage Info |
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Dosage Range
500 mg to 3,000 mg daily.
Most Common Dosage
Variable depending on whether the product is being taken for prevention or to treat a specific condition. For prevention, a dosage of 500 to 750 mg daily is commonly used. For therapeutic applications, a dosage of 2,000 to 3,000 mg daily is commonly used.
Dosage Forms
Capsules and bulk powder.
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Adult RDI
None established
Adult ODA
None established
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| Overview |
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Fructooligosaccharides (FOS) refer to a class of unique soluble non-digestible carbohydrates (ie. sugars) that occur naturally in a wide variety of edible foods throughout the plant kingdom. Since they are non-digestible, they pass through the human digestive tract largely unaltered. Their uniqueness manifests upon reaching the colon. In the colon, fructooligosaccharides are selectively utilized by the beneficial bacteria (known as bifidobacteria or bifidus) for growth and proliferation. A healthy microbial population influences digestion and absorption of nutrients, detoxification and elimination processes, and the immune system of the host.(1) Thus, fructooligosaccharides can provide important health benefits to individuals with less than optimal microbial get ecology. Whereas beneficial bacteria such as acidophilus and bifidus are frequently referred to as probiotics, fructooligosaccharides, which enhance and promote the growth of the probiotics are frequently referred to as prebiotics.
Since fructooligosaccharides are non-digestible, ingestion of FOS products provides almost no calories. They are also used as substitute sweeteners, containing approximately one-half the sweetness of sugar.(2) These properties also make them safe for individuals with diabetes to use. In addition to being used as an adjunctive health product in the nutritional supplement industry, FOS products are also being added to a variety of food products because they provide the combination of sweetness with low caloric value plus the additional health benefits that have been mentioned.(3) In animal studies, administration of FOS causes significant lowering of triglycerides, and to a lesser degree, cholesterol levels. However, this benefit has not been adequately explored in humans, so it is not appropriate to recommend FOS for blood lipid management at this time.(4)
Although fructooligosaccharides occur naturally in many foods, a large proportion of these products are now synthesized commercially by reacting glucose with b-fructofuranosidase enzymes, which are obtained from Aspergillus niger.(5) |
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| Toxicities & Precautions |
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Fructooligosaccharides are not digested or absorbed from the gastrointestinal tract of humans. Instead, they pass through the GI tract into the colon where they are used by bifidobacteria as a preferential source of food and energy.
General
There are no known toxicities associated with the use of fructooligosaccharides.
Side Effects
Ingesting doses that are too large (which varies from individual to individual) can cause increased colonic fermentation that can result in flatulence and/or diarrhea.(6)
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| Functions in the Body |
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Absorption of Minerals
In animal and human studies, administration of fructooligosaccharides creates a slightly lower pH (more acidic) in the large intestine, which enhances the absorption of minerals such as iron, calcium,(7) phosphorus, and magnesium.(8, 9)
Bifidobacteria
FOS is a food source that selectively potentiates the growth of bifidobacteria in the colon in both animals and humans. This tends to inhibit the number and growth of pathological bacteria, thereby improving overall health. In one study, 23 elderly individuals ingested 8 grams of FOS daily for 2 weeks. Examination of stool samples revealed an increase 10 times the number of bifidobacteria compared to levels at the beginning of the experiment.(10)
Dietary Fiber
Fructooligosaccharides are one of numerous types of dietary fiber that are known to enhance fecal bulk and transit time.(11)
Lactobacillus Bacteria
Although it is generally believed that fructooligosaccharides are primarily utilized by bifidobacteria in the large intestine, some research has reported that fructooligosaccharides can also be utilized by lactobacillus bacteria.(12, 13)
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| Clinical Applications |
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Antibiotic Therapy
It is becoming increasingly recognized that probiotic products containing beneficial bacteria such as lactobacillus and bifidobacteria organisms can be useful in the prevention and treatment of antibiotic-associated diarrhea.(14) Many of these commercial products also contain fructooligosaccharides, which enhance and promote the therapeutic benefits of the probiotic organisms. Even though no studies directly report that fructooligosaccharides are useful in this manner, the biochemical and physiological characteristics of these compounds tell us that this makes intuitive sense. |
Constipation
A 3-week trial on a population of hemodyalisis patients revealed that those patients who had fructooligosaccharides added to their basic dietary protocol had less constipation compared to patients receiving the same dietary protocol without FOS.(15) |
Dysbiosis
This is a term that refers to problems that are specifically related to or caused by an imbalance in the microbial population in the gastrointestinal tract. Absorption of toxins produced by the unfriendly bacteria can cause symptoms and problems far distant from the gastrointestinal tract. In one study, over 70% of children with dysbiosis had measurable levels of plasma endotoxins from the offending organisms in the GI tract.(16) Administration of bifidobacteria substantially reduced the level of toxins and helped normalize the intestinal microflora. Although fructooligosaccharides have not been studied for dysbiosis, numerous studies report and explain that FOS enhances the growth and proliferation of bifidobacteria, so it is logical to assume that FOS would be useful along with bifidobacteria in the prevention and treatment of dysbiosis. |
Gi Disorders
Probiotics are known to be therapeutically useful in a wide range of other GI problems. A sampling of such conditions includes irritable bowel syndrome, inflammatory bowel disease, lactose intolerance, and diarrhea caused by numerous bacterial and viral causes. In fact, it is probably safe to say that a majority of gastrointestinal problems could benefit from probiotic therapy. Although fructooligosaccharides have not been researched for these conditions, our knowledge of how FOS enhances the growth and proliferation of bifidobacteria makes FOS a logical choice to be used in conjunction with probiotics in the prevention and treatment of many gastrointestinal problems. |
Sweetening Agent
FOS functions as a substitute for sucrose as a sweetener. It has a sweetness intensity of approximately ½ that of sucrose. Since it is non-digestible by human digestive enzymes, it does not provide calories, does not upset blood sugar and insulin levels, and is therefore safe for individuals with diabetes.(17) |
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| Symptoms & Causes of Deficiency |
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Fructooligosaccharides are not classified as essential nutrients for humans, so no deficiency condition exists.
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| Footnotes |
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1 Boehm G, Jelinek J, Stahl B, et al. Prebiotics in infant formulas. J Clin Gastroenterol. Jul2004;38(6 Suppl):S76-9.
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2 Fishbein L, Kaplan M, Gough M. Fructooligosaccharides: a review. Vet Hum Toxicol. Apr1988;30(2):104-7.
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3 Young J. European market developments in prebiotic- and probiotic-containing foodstuffs. Br J Nutr. Oct1998;80(4):S231-3.
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4 Taylor GR, Williams CM. Effects of probiotics and prebiotics on blood lipids. Br J Nutr. Oct1998;80(4):S225-30.
View Abstract
5 Chiang CJ, Lee WC, Sheu DC, Duan KJ. Immobilization of beta-fructofuranosidases from Aspergillus on methacrylamide-based polymeric beads for production of fructooligosaccharides. Biotechnol Prog. Sep1997;13(5):577-82.
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6 Alles MS, et al. Bacterial fermentation of fructooligosaccharides and resistant starch in patients with an ileal pouch-anal anastomosis. Am J Clin Nutr. Nov1997;66(5):1286-92.
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7 Tahiri M, Tressol JC, Arnaud J, et al. Effect of short-chain fructooligosaccharides on intestinal calcium absorption and calcium status in postmenopausal women: a stable-isotope study. Am J Clin Nutr. Feb2003;77(2):449-57.
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8 Ohta A, Ohtsuki M, Baba S, et al. Effects of fructooligosaccharides on the absorption of iron, calcium and magnesium in iron-deficient anemic rats. J Nutr Sci Vitaminol. Tokyo. Jun1995;41(3):281-91.
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9 Ohta A, Ohtuki M, Takizawa T, et al. Effects of fructooligosaccharides on the absorption of magnesium and calcium by cecectomized rats. Int J Vitam Nutr Res. 1994;64(4):316-23.
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10 Mitsuoka T, Hidemasa H, Eida T. Effect of fructooligosaccharides on intestinal microflora. Die Nahrung. 1987;31(5-6):427-436.
View Abstract
11 Roberfroid MB. Functional effects of food components and the gastrointestinal system: chicory fructooligosaccharides. Nutr Rev. Nov1996;54(11 Pt 2):S38-42.
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12 Sghir A, Chow JM, Mackie RI. Continuous culture selection of bifidobacteria and lactobacilli from human faecal samples using fructooligosaccharide as selective substrate. J Appl Microbiol. Oct1998;85(4):769-77.
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13 Kaplan H, Hutkins RW. Fermentation of fructooligosaccharides by lactic acid bacteria and bifidobacteria. Appl Environ Microbiol. Jun2000;66(6):2682-4.
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14 Rolfe RD. The role of probiotic cultures in the control of gastrointestinal health. J Nutr. Feb2000;130(2S Suppl):396S-402S.
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15 Cockram DB, Hensley MK, Rodriguez M, et al. Safety and tolerance of medical nutritional products as sole sources of nutrition in people on hemodialysis. J Ren Nutr. Jan1998;8(1):25-33.
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16 Lykova EA, Bondarenko VM, Vorob'ev AA, et al. Bacterial endotoxinemia in children with intestinal dysbacteriosis. Zh Mikrobiol Epidemiol Immunobiol. May1999;(3):67-70.
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17 Luo J, Van Yperselle M, Rizkalla SW, et al. Chronic consumption of short-chain fructooligosaccharides does not affect basal hepatic glucose production or insulin resistance in type 2 diabetics. J Nutr. Jun2000;130(6):1572-7.
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