Quick answer
A prebiotic is a substance that microbes living in the body use selectively, with a documented health effect, according to a 2017 expert consensus. Most are fibers the gut cannot digest, such as inulin and other fructo-oligosaccharides. Prebiotics are food for microbes; probiotics are the live microbes themselves.1,2,3
Key facts
- The 2017 ISAPP consensus defines a prebiotic as a substrate selectively used by host microorganisms that confers a health benefit.1
- NCCIH describes prebiotics as nondigestible food components that selectively stimulate the growth or activity of desirable microorganisms.3
- Products that combine probiotics and prebiotics are called synbiotics.2,3
- In a trial in 26 healthy adults, up to 10 g a day of native inulin and up to 5 g a day of oligofructose were well tolerated.4
Prebiotic, probiotic, synbiotic, postbiotic
| Term | What it is |
|---|---|
| Prebiotic | A substance, usually an indigestible carbohydrate, that gut microbes use selectively |
| Probiotic | Live microorganisms that, in adequate amounts, confer a health benefit |
| Synbiotic | A product that combines probiotics and prebiotics |
| Postbiotic | Dead, intact or broken microorganisms, with or without their products, that confer a health benefit |
What counts as a prebiotic
Being a fiber is not enough. The 2017 definition requires that microbes use the substance selectively and that a health effect be documented. The same panel widened the idea to possibly include substances other than carbohydrates, and body sites other than the gut.1
On supplement and food labels the common prebiotic ingredients are inulin, often from chicory, its shorter chain form oligofructose, and other fructo-oligosaccharides.2,4
Gas and bloating
In a 2010 crossover trial in 26 healthy adults, inulin fibers tended to increase digestive symptoms mildly, most often flatulence and then bloating, and a 10 g dose of oligofructose increased symptoms substantially compared with control. If you have a digestive condition, ask your doctor before adding prebiotic fiber.4
Questions people ask
What is the difference between prebiotics and probiotics?
Probiotics are live microorganisms. Prebiotics are what certain microorganisms feed on, usually fibers your own enzymes cannot digest. A product that contains both is a synbiotic.2,3
Does a drink labeled prebiotic contain a prebiotic?
It contains an ingredient sold as one, usually added inulin or another fiber. Whether that ingredient, at that amount, meets the 2017 definition depends on evidence of selective use by gut microbes and a documented health effect.1
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Sources
- Gibson GR, Hutkins R, Sanders ME, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nat Rev Gastroenterol Hepatol. 2017;14(8):491-502. Opened 2026-10-07.
- Office of Dietary Supplements, National Institutes of Health. Probiotics: Fact Sheet for Health Professionals. Updated March 25, 2025. Opened 2026-10-07.
- National Center for Complementary and Integrative Health. Probiotics: What You Need To Know. Opened 2026-10-07.
- Bonnema AL, Kolberg LW, Thomas W, Slavin JL. Gastrointestinal tolerance of chicory inulin products. J Am Diet Assoc. 2010;110(6):865-868. Opened 2026-10-07.
- Hill C, Guarner F, Reid G, et al. Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.