23/10/2026
When people talk about “supporting the microbiome”, they often mix up prebiotics, probiotics, postbiotics, and psychobiotics.
- Prebiotic (fibre):
A prebiotic is a substrate that host microorganisms use selectively and that produces a health benefit, such as:
• Inulin and fructooligosaccharides (FOS).
• Galactooligosaccharides (GOS).
• Resistant starch.
• Certain beta-glucans, and more.
Prebiotics provide fermentable substrates for microbial metabolism. Fermentation can produce short-chain fatty acids that interact with the intestinal lining, immune signalling, gut motility, and energy metabolism.
The practical implication is that microbial diversity depends not only on which organisms are present, but also on what they are consistently fed. A diet rich in varied plant foods generally provides a broader range of substrates than a highly restricted, ultra-processed dietary pattern.
- Probiotics:
A probiotic is a live microorganism that, when administered in an adequate amount, provides a demonstrated health benefit to the host.
Effects are often strain-specific, and a product that helps one outcome may have no meaningful effect on another.
A probiotic is not necessarily a permanent replacement for a person’s microbiome. Many strains act transiently as they are consumed, and outcomes depend on the strain, dose, host physiology, baseline microbiome, diet, and clinical context.
- Postbiotics:
A postbiotic is a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host, which may contain:
• Inactivated microbial cells.
• Cell-wall components.
• Microbial proteins.
• Structural fragments.
• Metabolites that remain within a defined preparation.
• Combinations of these components.
Postbiotics also include microbial metabolites, such as some vitamins, short-chain fatty acids, and other compounds the body relies on.
Psychobiotics:
They influence mental or neurological processes through the microbiota–gut–brain axis. Reviews describe potential effects on mood, cognition, stress responses and emotional regulation.
This matters when considering neuroinflammation and even neurodegeneration, which may have started in the gut.