A prebiotic is a substance that gut microorganisms selectively use and that, as a result, gives a health benefit. Most are complex carbohydrates such as inulin and other fructo-oligosaccharides; products combining them with probiotics are called synbiotics.
Also known as: prebiotic, prebiotic fiber, fructo-oligosaccharides, FOS, synbiotics.
Prebiotics are a category, not one substance, and trials of each one used different amounts, so we do not list one.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling.
What counts: in 2017 an expert panel of the International Scientific Association for Probiotics and Prebiotics (ISAPP) defined a prebiotic as a substrate that host microorganisms selectively use to give a health benefit, and said a benefit must be documented before a substance can be called a prebiotic. The panel aimed to make use of the word consistent in research, marketing and regulation (Gibson 2017). ODS describes prebiotics as mainly complex carbohydrates, such as inulin, that gut microbes use as fuel.
What studies show: evidence is specific to each prebiotic. For chicory inulin-type fructans, a 2024 meta-analysis of 32 studies found about 0.97 kg more weight loss than placebo, with small drops in BMI and waist size (about 1 cm) (Reimer 2024). Two of its three authors work for BENEO, a company that makes prebiotic fructans, and the third has received consulting fees on prebiotics.
Safety: the sources here do not describe side effects or drug interactions for prebiotics as a group.
Prebiotics are meant to be used by gut microbes rather than absorbed like a drug (Gibson 2017), so a half-life or time to peak does not apply.
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