Prebiotics

What are prebiotics?

Updated 4 Nov 2026

Short answer

Prebiotics are substances that gut microbes use selectively, in a way that gives a health benefit.[1] Most are carbohydrates that the upper gut does not digest, and microbes use them as fuel.[2][3]

The main groups are fructans (inulin and fructo-oligosaccharides, or FOS), galacto-oligosaccharides (GOS), lactulose, resistant starch, polydextrose and pectin oligosaccharides.[2] They occur naturally in foods such as garlic, onion, chicory and asparagus. The amounts in food are low, so some are also made on a large scale and added to foods.[2] A 2025 British guideline on constipation accepted trials that gave fiber supplements, including prebiotic fiber, as pills, capsules, powder sachets, solutions or fortified foods and drinks.[4]

Prebiotics are different from probiotics, which are live microbes. Synbiotics contain both.[3]

Sources (4)

  1. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Gibson GR, Hutkins R, Sanders ME, Prescott SL, Reimer RA, Salminen SJ, et al. Nat Rev Gastroenterol Hepatol, 2017. PMID 28611480
  2. Prebiotics and Probiotics for Gastrointestinal Disorders. Rau S, Gregg A, Yaceczko S, Limketkai B Nutrients, 2024. PMID 38542689
  3. Probiotics: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. ods.od.nih.gov
  4. British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. Dimidi E, van der Schoot A, Barrett K, Farmer AD, Lomer MC, Scott SM, et al. J Hum Nutr Diet, 2025. PMID 41081513

More about prebiotics

Do prebiotics change your gut bacteria?How long do prebiotics take to work?Which foods contain prebiotics?What are prebiotics used for?Is a synbiotic better than a prebiotic alone?Are prebiotics the same as fiber?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.