Dietary components — usually fibres — that you do not digest yourself but that selectively feed your beneficial microbes and thereby support health.

Which foods contain prebiotics?

In chicory, leek, onion, garlic, asparagus, banana, pulses, oats and cooled cooked starch (resistant starch), among others.

Is every fibre a prebiotic?

No. A prebiotic is selectively used by beneficial micro-organisms. All prebiotics are fibres or fibre-like, but not every fibre is prebiotic.

Do I need a supplement?

Usually not. A varied, plant-rich diet with many different fibres is the most natural source. Supplements can provide targeted top-ups.

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Prebiotics

EN: prebiotics · related terms: probiotics, synbiotics, postbiotics

Definition Prebiotics are dietary components — usually certain fibres — that you do not digest yourself, but that are selectively used by beneficial micro-organisms and thereby confer a health benefit. They act as food for your microbiome and stimulate the production of beneficial substances such as short-chain fatty acids.

In plain language

Put simply, prebiotics are the food for your good gut bacteria. They are pieces of fibre that your own digestion skips over, but that your microbes love to eat. Think of inulin from chicory, leek, onion and asparagus, of fructo- and galacto-oligosaccharides, and of resistant starch from cooled potatoes or rice. When your microbes ferment these fibres, they make short-chain fatty acids such as butyrate — precisely the substances that feed your gut wall and calm your immune system. The practical insight: you do not necessarily have to take a supplement. A varied, plant-rich plate with many different fibres is the most natural way to feed your microbiome. A rule of thumb from many researchers: aim for variety — the more different plants per week, the richer your microbial garden.

The science behind

According to the ISAPP consensus (Gibson et al. 2017), a prebiotic is 'a substrate that is selectively utilised by host micro-organisms conferring a health benefit'. The classics are inulin-type fructans (inulin, FOS) and galacto-oligosaccharides (GOS); resistant starch and certain polyphenols also display prebiotic properties.

• Selectivity. Not every fibre is a prebiotic; what matters is selective utilisation by beneficial taxa (for example Bifidobacterium and butyrate producers).
• Fermentation into SCFA. The main route of the health effect: prebiotics provide the raw material for short-chain fatty acids.
• Barrier & immune. Through SCFA and an altered microbial composition, prebiotics influence the gut barrier and the inflammatory tone.
• Dose & tolerance. High doses of fermentable fibres can cause gas; gradual build-up and variety are recommended.

Prebiotics are the entry point of co-metabolism: they help determine which micro-organisms receive substrate and therefore which postbiotics arise. Together with living micro-organisms they form synbiotics. My InnerSelfie reads fibre utilisation as part of the broader gut environment. This reading is supportive and observational — not a medical diagnosis.

Related concepts

Probiotics Synbiotics Postbiotics (SCFA)Microbiome Co-metabolism

Where appropriate — support: targeted prebiotic fibres can supplement what a busy diet does not always manage, always alongside a plant-rich plate. Discover the My Key Nutrients range.

Scientific references

• Gibson et al. (2017), ISAPP consensus on the definition of prebiotics, Nature Reviews Gastroenterology & Hepatology.
• Prebiotics, Probiotics and Nutraceuticals.
• Emily Leeming, Genius Gut.

Frequently asked questions

What are prebiotics?: Dietary components — usually fibres — that you do not digest yourself but that selectively feed your beneficial microbes and thereby support health.
Which foods contain prebiotics?: In chicory, leek, onion, garlic, asparagus, banana, pulses, oats and cooled cooked starch (resistant starch), among others.
Is every fibre a prebiotic?: No. A prebiotic is selectively used by beneficial micro-organisms. All prebiotics are fibres or fibre-like, but not every fibre is prebiotic.
Do I need a supplement?: Usually not. A varied, plant-rich diet with many different fibres is the most natural source. Supplements can provide targeted top-ups.