what is fos powder
Tweet. Fructooligosaccharides (FOS) are short-chain polymers comprised of D-fructose and D-glucose, which are not metabolized by the body like simple sugars are, and are therefore considered non-digestible oligosaccharides.AUTION: Some individuals taking FOS may experience gastrointestinal bloating that persists longer than 1-2 weeks, possibly due to unfriendly microbes feeding on FOS. In such cases, this product should be discontinued.