Fructo-oligosaccharides (FOS)
What is it? Overview Usage Side Effects and Warnings

What is Fructo-oligosaccharides (FOS)?

Fructo-oligosaccharides (FOS) are starches that the human body cannot fully digest. Inulin and galacto-oligosaccharides (GOS) are similar substances also discussed in this article.

When a person consumes FOS, the undigested portions provide nourishment for bacteria in the digestive tract. “Friendly” bacteria ( probiotics ) may respond particularly well to this nourishment. Because FOS feed probiotics, they are sometimes called a “prebiotic.”

Low doses of FOS are often provided along with probiotic supplements to aid their growth. High doses of FOS (and related substances) have been advocated for a variety of health conditions. However, currently, the available scientific evidence for benefit remains more negative than positive.

Animal studies hint that FOS, GOS, and inulin can significantly improve cholesterol profile; however, study outcomes in humans have been inconsistent at best. 1 2 3 4 5 6 One study found that while inulin might produce a short-term benefit, any such benefit disappears after six months of use. 7 At most, it appears that FOS might improve cholesterol profiles by 5%, an amount too small to make much of a difference in most circumstances. These relatively poor results might be due to that fact that humans cannot tolerate doses of FOS much above 15 g daily without developing gastrointestinal side effects.

FOS has also been suggested for preventing traveler’s diarrhea . However, in a large (244-participant) double-blind study, FOS at a dose of 10 g daily again offered...

Safety Issues

FOS appear to be generally safe. However, they can cause bloating, flatulence, and intestinal discomfort, especially when taken at doses of 15 g or higher daily. 8 People with lactose intolerance may particularly suffer from these side effects. 9