Fructo-oligosaccharides (fos)
Fructo-oligosaccharides (fos)


Fructo-oligosaccharides (FOS) are plant sugars that occur in many fruits and vegetables. They can also be made in a lab and are used as prebiotics.

FOS do not get digested until they reach the colon. In the colon, they are digested by good bacteria. This helps the good bacteria to grow, which is why they are used as prebiotics. Prebiotics act as food for probiotics (good bacteria).

People use FOS for constipation, obesity, diabetes, travelers' diarrhea, high cholesterol, and many other conditions, but there is no good scientific evidence to support these uses.

Don't confuse prebiotics with probiotics. These are not the same.
When taken by mouth: FOS are possibly safe in doses less than 30 grams daily for up to 4 weeks. They can cause gas, bloating, and stomach pain. These effects are usually mild if the dose is less than 10 grams daily.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if FOS are safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: FOS are possibly safe when added to infant formula or cow's milk and given to healthy infants. The doses used in research are 4 grams of FOS per liter of formula, or up to 1 gram of FOS per kilogram of infant body weight.


There is interest in using FOS for a number of purposes, but there isn't enough reliable information to say whether it might be helpful.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
Insufficient evidence Effectiveness definitions

Dosing & administration

FOS has most often been used by adults in doses of 10 grams by mouth daily for up to 4 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

It is not known if Fructo-Oligosaccharides (FOS) interacts with any medicines. Before taking Fructo-Oligosaccharides (FOS), talk with your healthcare professional if you take any medications.

Interactions with herbs & supplements

Iron: FOS might increase how much iron the body absorbs from supplements.

Interactions with foods

There are no known interactions with foods.
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This monograph was last reviewed on 22/02/2023 11:00:00 and last updated on 05/05/2022 08:05:28. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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