What are postbiotics?

The beneficial substances and inactive cell components that micro-organisms leave behind, with short-chain fatty acids such as butyrate as the best-known example.

What is the difference between pre-, pro- and postbiotics?

Prebiotics are the food for your microbes, probiotics are live beneficial micro-organisms, and postbiotics are what your microbes make from them.

Why is butyrate important?

Butyrate is the main fuel for your gut wall cells, helps keep the barrier closed and calms an overactive immune defence.

How do I increase my SCFA?

Mainly by eating more and more varied fibre — vegetables, pulses, whole grains, fruit — so that your fermenting bacteria get enough raw material.

CosmoLexicon › Postbiotics (SCFA)

Postbiotics (SCFA)

EN: postbiotics · related terms: prebiotics, probiotics, co-metabolism

Definition Postbiotics are the beneficial substances and inactive microbial components that your micro-organisms leave behind. The best known are the short-chain fatty acids (SCFA) — butyrate, propionate and acetate — that arise when gut bacteria ferment fibre. These molecules feed the gut wall, steer the immune system and send signals to organs all the way to the brain.

In plain language

If prebiotics are the food and probiotics the cooks, then postbiotics are the meal that comes out of it. They are the useful substances your bacteria make when they ferment fibre. The most important group are the short-chain fatty acids, with butyrate as the star. Butyrate is the favourite fuel of your gut wall cells, helps keep the gut barrier closed, calms an overactive immune defence and even sends signals to your brain. Other short-chain fatty acids, propionate and acetate, play a part in your metabolism and satiety. The beauty of it is: you do not produce postbiotics directly by swallowing a pill, but by feeding your bacteria well — with fibre from vegetables, pulses, whole grains and fruit. That is how health works from within: you supply the raw material, your microbes do the rest.

The science behind

The international scientific consensus (ISAPP, Salminen et al. 2021) defines a postbiotic as 'a preparation of inactive micro-organisms and/or their components that confers a health benefit on the host'. In a broader sense, microbial metabolites — with the short-chain fatty acids (SCFA) at the forefront — are also regarded as a postbiotic effect.

• Butyrate. Primary energy source for colonocytes; strengthens the gut barrier, induces regulatory T cells and acts as a histone deacetylase inhibitor (epigenetic signalling).
• Propionate. Plays a part in liver and glucose metabolism and in satiety signals.
• Acetate. The most abundant SCFA; substrate for peripheral metabolism and signalling.
• Receptors. SCFA act among other things via the free fatty acid receptors FFAR2/FFAR3 and thereby influence immune, metabolic and enteroendocrine pathways (for example GLP-1 and PYY release).

SCFA form a central link in co-metabolism: they only arise through microbial fermentation of fibre that the host does not digest itself, and then act systemically via the gut-organ axes. Within My InnerSelfie, robust butyrate formation counts as a marker of a resilient gut environment. This reading is supportive and observational — not a medical diagnosis.

Related concepts

Prebiotics Probiotics Synbiotics Co-metabolism Gut-organ axes Microbiome

Where appropriate — support: if your butyrate formation is low, targeted fibre and polyphenol supplementation can feed the right fermenting micro-organisms. Discover the My Key Nutrients range.

Scientific references

• Salminen et al. (2021), ISAPP consensus on the definition of postbiotics, Nature Reviews Gastroenterology & Hepatology.
• Lee et al. (2024), The human gut microbiome in health and disease.
• Specialized Pro-resolving Mediators — Resolution of Inflammation.
• Emily Leeming, Genius Gut.

Frequently asked questions

What are postbiotics?: The beneficial substances and inactive cell components that micro-organisms leave behind, with short-chain fatty acids such as butyrate as the best-known example.
What is the difference between pre-, pro- and postbiotics?: Prebiotics are the food for your microbes, probiotics are live beneficial micro-organisms, and postbiotics are what your microbes make from them.
Why is butyrate important?: Butyrate is the main fuel for your gut wall cells, helps keep the barrier closed and calms an overactive immune defence.
How do I increase my SCFA?: Mainly by eating more and more varied fibre — vegetables, pulses, whole grains, fruit — so that your fermenting bacteria get enough raw material.