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Fructo-oligosaccharides (FOS) and Other Oligosaccharides


What does fructo-oligosaccharides (fos) and other oligosaccharides do?

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.

Clinical studies have shown that administering FOS, GOS, or inulin can increase the number of these friendly bacteria in the colon while simultaneously reducing the population of harmful bacteria.5 6 7 8 9 Other benefits noted with FOS, GOS, or inulin supplementation include increased production of beneficial short-chain fatty acids such as butyrate, increased absorption of calcium and magnesium, and improved elimination of toxic compounds.10 11

Because FOS, GOS, and inulin improve colon function and increase the number of friendly bacteria, one might expect these compounds would help relieve the symptoms of irritable bowel syndrome. However, a double-blind trial found no clear benefit with FOS supplementation (2 grams three times daily) in patients with this condition.12 Experimental studies with FOS in animals suggest a possible benefit in lowering blood sugar levels in people with diabetes and in reducing elevated blood cholesterol and triglyceride levels.13

In a double-blind trial of middle-aged men and women with elevated cholesterol and triglyceride levels, supplementation with inulin (10 grams per day for eight weeks) significantly reduced insulin concentrations (suggesting an improvement in blood-glucose control) and significantly lowered triglyceride levels.14 In a preliminary trial, administration of FOS (8 grams per day for two weeks) significantly lowered fasting blood-sugar levels and serum total-cholesterol levels in patients with type 2 (non-insulin-dependent) diabetes.15 However, in another trial, people with type 2 diabetes supplementing with FOS (15 grams per day) for 20 days found no effect on blood-glucose or lipid levels.16 In addition, double-blind trials of healthy people showed that supplementing with FOS or GOS for eight weeks had no effect on blood-sugar levels, insulin secretion, or blood lipids.17 18 Because of these conflicting results, more research is needed to determine the effect of FOS and inulin on diabetes and lipid levels.

Several double-blind trials have looked at the ability of FOS or inulin to lower blood cholesterol and triglyceride levels. These trials have shown that in people with elevated total cholesterol or triglyceride levels, including people with type 2 (adult onset) 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.19 20 21 22 In people with normal or low cholesterol or triglyceride levels, FOS or inulin produced little effect.23 24 25

Where  is fructo-oligosaccharides (fos) and other oligosaccharides found?

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,26 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.27 In fact, inulin is a significant part of the daily diet of most of the world’s population.28 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.

FOS, GOS, and inulin have been used in connection with the following conditions (refer to the individual health concern for complete information):


Health Concerns

Elevated triglyceride levels


Pre- and post-surgery health

Reliable and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.


Who is likely to be deficient of fructo-oligosaccharides (fos) and other oligosaccharides?

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

How much fructo-oligosaccharides (fos) and other oligosaccharides is usually taken?

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.

Are there any side effects or interactions with fructo-oligosaccharides (fos) and other oligosaccharides?

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.29Allergy 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.

At the time of writing, there were no well-known drug interactions with Fructo-oligosaccharides (FOS) and Other Oligosaccharides.