PREBIOTICS

ISAPP-Defined Science Feed your microbiome. Transform your health. Prebiotics are substrates that selectively nourish beneficial microorganisms in your body — unlocking real, measurable improvements to digestive, immune, and metabolic health. Scientific Definition — ISAPP 2017 "A substrate that is selectively utilized by host microorganisms conferring a health benefit." 38+ trillion gut microbes 73+ ISAPP resources 2017 consensus definition What is a prebiotic Not all fibres are prebiotics — but some are extraordinary. Prebiotics encompass many types of substances, but the most studied are specific dietary fibres. The key distinction: a prebiotic must be selectively fermented by beneficial microorganisms and shown to produce a health benefit. Most dietary fibres don't clear that bar. "Substrates that are selectively utilized by host microorganisms conferring a health benefit." ISAPP Consensus Definition — Gibson et al., Nature Reviews Gastroenterology & Hepatology, 2017 01 Resistant to digestion Passes through the upper gastrointestinal tract without being broken down by stomach acid or digestive enzymes. 02 Selectively fermented by beneficial microbes Used specifically by health-promoting bacteria — particularly Bifidobacterium and Lactobacillus — rather than potentially harmful microorganisms. 03 Confers a demonstrable health benefit The microbiome alteration must translate into a measurable improvement in host health — digestive, immune, metabolic, or otherwise. Mechanism How prebiotics work in the body Prebiotics act upstream of probiotics — they're the food that beneficial microorganisms require to thrive. The cascade of effects extends well beyond digestion. Step 01 🌿 You consume the substrate Prebiotic fibres and polyphenols reach the large intestine intact — resisting digestion in the stomach and small intestine. Step 02 🦠 Beneficial bacteria selectively ferment Bifidobacterium and Lactobacillus preferentially metabolise the prebiotic substrate, gaining a competitive advantage. Step 03 ⚗️ Metabolites are produced Fermentation produces short-chain fatty acids — acetate, propionate, and butyrate — that feed the intestinal lining and reduce inflammation. Step 04 🔬 The microbiome shifts Consistent prebiotic intake changes the composition and diversity of the gut microbiota — favouring beneficial species. Step 05 💚 Health benefits emerge Improved digestion, enhanced immune response, better mineral absorption, and more regulated satiety signalling. Step 06 📊 Evidence must be demonstrated Per ISAPP criteria, the health benefit must be substantiated — not assumed. Clinical validation is central to credible prebiotic science. Evidence-based benefits What prebiotics have been shown to do Across decades of research, specific prebiotics have demonstrated measurable effects in controlled studies. Improved digestive function Prebiotics such as inulin-type fructans have demonstrated consistent improvements in stool frequency, consistency, and transit time. Support of the body's natural defences Butyrate produced via prebiotic fermentation supports intestinal barrier integrity and modulates immune cell activity. Improved mineral absorption Specific prebiotic fibres have been shown to enhance calcium and magnesium absorption, with implications for bone health. Satiety and energy balance Prebiotic fermentation stimulates the release of gut hormones including GLP-1 and PYY, which regulate appetite and metabolic health. Microbiome diversity Regular prebiotic consumption selectively enriches Bifidobacterium and other beneficial taxa, supporting a more diverse and resilient gut ecosystem. Cognitive and brain health (emerging) Early research suggests prebiotic fibre and short-chain fatty acids may influence cognitive performance and mood via the gut-brain axis. Natural sources Where prebiotics occur in food Prebiotics are found naturally in a range of plant foods — though typically at low concentrations. This is why concentrated prebiotic supplements and functional ingredients have attracted significant research and commercial interest. 🧅 Onions & garlic Rich in inulin and fructooligosaccharides (FOS). 🍌 Unripe bananas Contains resistant starch that acts as a prebiotic substrate. 🌿 Chicory root Primary commercial source of inulin — the most well-characterised prebiotic fibre. 🫐 Fruits & berries Polyphenols in blueberries, apples, and citrus selectively modulate gut bacteria. 🌾 Oats & barley Beta-glucan has documented prebiotic-like effects and cardiovascular benefits. 🫘 Legumes Lentils, chickpeas, and beans provide GOS and resistant starch. ♻️ Agricultural byproducts Apple pomace, citrus peel, and brassica waste — emerging upcycled prebiotic sources. The upcycled opportunity: Fruit and vegetable processing byproducts — apple pomace, citrus peel, brassica trimmings — are naturally concentrated in the same polyphenols and fibres found in whole foods. Certified upcycled prebiotic powders represent a genuine white space: the same or superior prebiotic function, with a sustainability story no conventional brand can authentically replicate. Scientific authority Grounded in ISAPP consensus science The International Scientific Association for Probiotics and Prebiotics (ISAPP) is the global scientific body responsible for setting the consensus definitions and criteria that govern this category. 🏛️ Consensus definition (2017) The ISAPP definition is the scientific and regulatory benchmark globally for prebiotic claims. 🔬 Validation & health claims ISAPP has published guidance on substantiating prebiotic status and navigating health claim requirements. 📡 Ongoing research ISAPP monitors emerging evidence across 73+ resources — from oral microbiota to cognitive health. Key resources Infographic Prebiotics — the visual explainer → Infographic Understanding prebiotics and fibre → Video What is a prebiotic? → Research tool Prebiotic R&D — validation & health claim guide → Infographic Effects of prebiotics on the microbiota → ISAPP Hub All 73+ ISAPP prebiotic resources ↗ Disclaimer: The contents of this page draw on materials from the International Scientific Association for Probiotics and Prebiotics (ISAPP) and are provided for informational and educational purposes only. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Source: isappscience.org/topic/prebiotics/