Prebiotics
Inulin / FOS / GOS / chicory root fibre · Gut
Food for the bacteria you already have, rather than more bacteria — and the distinction is the whole point.
What the evidence says
Prebiotic fibres reliably shift the gut microbiome and increase short-chain fatty acid production — that part is well demonstrated. Translating that into symptom or health outcomes is less consistent, with the best signals in regularity and calcium absorption. Related entries: probiotics, soluble fibre and psyllium husk, which overlap heavily with this one.
What studies used
Trials commonly used 5–10 g/day, often built up gradually because of gas. Published studies had not established a preferred timing.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- Gas and bloating are extremely common at the start and are the main reason people quit
- Inulin and FOS are high-FODMAP and frequently make IBS symptoms worse rather than better
Evidence base
established literature
Strong human evidence: either a phase 3 or 4 trial report alongside review-level evidence, or ten or more randomised controlled trial reports.
This letter measures how much human research exists, not whether it works for you — the tier above (Moderate) is the read on quality.
Research (12)
- Fiber and prebiotics: mechanisms and health benefitsNutrients · 2013
- Dietary fiber and prebiotics and the gastrointestinal microbiotaGut Microbes · 2017
- The Prebiotic Potential of Inulin-Type Fructans: A Systematic ReviewAdv Nutr · 2022
- Dietary fibre in gastrointestinal health and diseaseNat Rev Gastroenterol Hepatol · 2021
- Fiber and Prebiotic Interventions in Pediatric Inflammatory Bowel Disease: What Role Does the Gut Microbiome Play?Nutrients · 2020
- Fiber and prebiotic supplementation in enteral nutrition: A systematic review and meta-analysisWorld J Gastroenterol · 2015
- The gut microbiota in menopause: Is there a role for prebiotic and probiotic solutions?Post Reprod Health · 2025
- Red Ginseng Dietary Fiber Shows Prebiotic Potential by Modulating Gut Microbiota in DogsMicrobiol Spectr · 2023
- Inulin: Properties, health benefits and food applicationsCarbohydr Polym · 2016
- Designing future prebiotic fiber to target metabolic syndromeNutrition · 2014
- Evidence-based dietary recommendations for patients with psoriasis: A systematic reviewClin Nutr · 2025
- Effects of a diverse prebiotic fibre blend on inflammation, the gut microbiota and affective symptoms in metabolic syndrome: a pilot open-label randomised controlled trialBr J Nutr · 2024
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