Fructo-oligosaccharides (FOS) and Other Oligosaccharides

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The term “oligosaccharide” refers to a short chain of sugar molecules (“oligo” means “few” and “saccharide” means “sugar.”) Fructo-oligosaccharides (FOS) and inulin, which are found in many vegetables, consist of short chains of fructose molecules. Galacto-oligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans.1 , 2 , 3 , 4 When oligosaccharides are consumed, the undigested portion serves as food for “friendly” bacteria, such as Bifidobacteria and Lactobacillus species.

What Are Star Ratings?

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.

2 Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

This supplement has been used in connection with the following health conditions:

Used for Why
2 Stars
Eczema (Galacto-oligosaccharides)
90% galacto-oligosaccharides and 10% fructo-oligosaccharides mixture added daily to infant formula
In one study, adding a mixture of 90% galacto-oligosaccharides and 10% fructo-oligosaccharides to infant formula prevented the development of eczema in babies who were at high risk of developing eczema.

In a double-blind trial, the addition of a mixture of 90% galacto-oligosaccharides and 10% fructo-oligosaccharides to infant formula prevented the development of eczema in infants who were at high risk of developing eczema. The incidence of eczema in the first six months of life was 9.8% in the group receiving oligosaccharides, compared with 23.1% in the placebo group, a statistically significant difference. The product used in this study was designed to mimic the oligosaccharide content of human milk, and was added at a concentration of 0.8 grams per 100 ml.

2 Stars
High Triglycerides
8 to 20 grams daily
Several trials have shown that FOS supplementation lowers triglycerides in people with elevated levels.

Several double-blind trials have evaluated the efficacy of fructo-oligosaccharides (FOS) or inulin (a related compound) for lowering blood cholesterol and triglyceride levels. These trials have shown that in individuals with elevated total cholesterol or triglyceride levels, including people with type 2 diabetes, FOS or inulin (in amounts ranging from 8 to 20 grams daily) produced significant reductions in triglyceride levels; however, the effect on cholesterol levels was inconsistent. In people with normal or low cholesterol or triglyceride levels, FOS or inulin produced little effect.

1 Star
Indigestion, Heartburn, and Low Stomach Acidity
5 grams per day
Supplementing with fructo-oligosaccharides may help relieve abdominal discomfort, fullness, constipation, urgency, and diarrhea.
In a double-blind trial, supplementation with 5 grams of fructo-oligosaccharides per day for six weeks was significantly more effective than a placebo at relieving symptoms of dyspepsia such as such as abdominal discomfort, fullness, constipation, urgency, and diarrhea. The average symptom severity decreased by 44% in the group receiving fructo-oligosaccharides.
1 Star
Pre- and Post-Surgery Health
Refer to label instructions
Supplementing with fructo-oligosaccharides (FOS) appears to improve iron absorption and restore iron levels, which may be reduced after surgery.

One preliminary study found iron levels to be reduced after both minor and major surgeries, and iron supplementation prior to surgery was not able to prevent this reduction. A controlled trial found that intravenous iron was more effective than oral iron for restoring normal iron levels after spinal surgery in children. One animal study reported that supplementation with fructo-oligosaccharides (FOS) improved the absorption of iron and prevented anemia after surgery, but no human trials have been done to confirm this finding. Some researchers speculate that iron deficiency after a trauma such as surgery is an important mechanism for avoiding infection, and they suggest that iron supplements should not be given after surgery.

1 Star
Type 2 Diabetes
Refer to label instructions
In one trial, supplementing with fructo-oligosaccharides significantly lowered fasting blood-sugar levels and serum total-cholesterol levels in people with type 2 diabetes.
In a preliminary trial, supplementation with fructo-oligosaccharides (FOS) (8 grams per day for two weeks) significantly lowered fasting blood-sugar levels and serum total-cholesterol levels in people with type 2 diabetes. However, in another trial, supplementing with FOS (15 grams per day) for 20 days had no effect on blood-glucose or lipid levels in people with type 2 diabetes. In addition, some double-blind trials showed that supplementing with FOS or galacto-oligosaccharides (GOS) for eight weeks had no effect on blood-sugar levels, insulin secretion, or blood lipids in healthy people. Because of these conflicting results, more research is needed to determine the effect of FOS on diabetes and lipid levels.

How It Works

How to Use It

The average daily intake of oligosaccharides by people in the United States is estimated to be about 800 to 1,000 mg. For the promotion of healthy bacterial flora, the usual recommendation for FOS, GOS, or inulin is 2,000 to 3,000 mg per day with meals. In the studies on diabetes and high blood lipids (cholesterol and triglycerides), amounts ranged from 8 to 20 grams per day.

Where to Find It

FOS and inulin are found naturally in Jerusalem artichoke, burdock, chicory, leeks, onions, and asparagus. FOS products derived from chicory root contain significant quantities of inulin,5 a fiber widely distributed in fruits, vegetables and plants, which is classified as a food ingredient (not as an additive) and is considered to be safe to eat.6 In fact, inulin is a significant part of the daily diet of most of the world’s population.7 FOS can also be synthesized by enzymes of the fungus Apergillus niger acting on sucrose. GOS is naturally found in soybeans and can be synthesized from lactose (milk sugar). FOS, GOS, and inulin are available as nutritional supplements in capsules, tablets, and as a powder.

Possible Deficiencies

As FOS, GOS, and inulin are not essential nutrients, no deficiency state exists.


Interactions with Supplements, Foods, & Other Compounds

At the time of writing, there were no well-known supplement or food interactions with this supplement.

Interactions with Medicines

As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

Generally, oligosaccharides are well tolerated. Some people reported increased flatulence in some of the studies. At higher levels of intake, that is, in excess of 40 grams per day, FOS and the other oligosaccharides may induce diarrhea.

There is a report of a 39-year old man having a life-threatening allergic reaction after consuming high amounts of inulin from multiple sources, including FOS.8 Allergy to inulin in this person was confirmed by laboratory tests. Such sensitivities are extremely rare. People with a confirmed sensitivity to inulin should probably avoid FOS.


1. Molis C, Flourie B, Ouarne F, et al. Digestion, excretion, and energy value of fructooligosaccharides in healthy humans. Am J Clin Nutr 1996;64:324-8.

2. van Dokkum W, Wezendonk B, Srikumar TS, van den Heuvel EG. Effect of nondigestible oligosaccharides on large-bowel functions, blood lipid concentrations and glucose absorption in young healthy male subjects. Eur J Clin Nutr 1999;53:1-7.

3. Alles MS, Hautvast JGA, Nagengast FM, et al. Fate of fructo-oligosaccharides in the human intestine. Br J Nutr 1996;76:211-21.

4. Roberfroid M. Dietary fibre, inulin and oligofructose. A review comparing their physiological effects. Crit Rev Food Sci Nutr 1993;33:103-48 [review].

5. Duke, JA. Handbook of Phytochemical Constituents of GRAS Herbs and Other Economic Plants. Boca Raton, FL: CRC Press, 1992.

6. Carabin IG, Flamm WG. Evaluation of safety of inulin and oligofructose as dietary fiber. Regul Toxicol Pharmacol 1999;30:268-82 [review].

7. Coussement PA. Inulin and oligofructose: safe intakes and legal status. J Nutr 1999;129:1412S-7S [review].

8. Gay-Crosier F, Schreiber G, Hauser C. Anaphylaxis from inulin in vegetables and processed food. N Engl J Med 2000;342:1372 [letter].