Microbiome science

Postbiotics

Also called: bacterial metabolites

Postbiotics are bioactive compounds produced by bacteria during fermentation, including short-chain fatty acids (butyrate, propionate, acetate), bacterial cell wall fragments, peptides and exopolysaccharides. The category is new (formally defined by ISAPP in 2021) and the consumer evidence is early. Whole-food sources like fermented vegetables and aged cheese deliver postbiotics naturally; supplements are mostly speculative.

Where postbiotics sit

  • Probiotics: live bacteria you take in.
  • Prebiotics: food (fibre) you eat that feeds existing bacteria.
  • Postbiotics: the byproducts bacteria produce while doing their job.
  • Synbiotics: probiotic + prebiotic combination.

What counts as a postbiotic

ISAPP's 2021 definition: a preparation of inanimate (non-living) microorganisms or their components that confers a health benefit on the host. The 'inanimate' part is key, postbiotics are by definition not alive, which means they are more shelf-stable and predictable than probiotics. Includes pasteurised Akkermansia, heat-killed Lactobacillus preparations, butyrate, beta-glucans from yeast cell walls, and others.

Best-evidenced postbiotics

  • Pasteurised Akkermansia muciniphila: 3-month trial showed modest weight loss and insulin sensitivity improvement.
  • Heat-killed Lactobacillus paracasei MCC1849: small evidence for upper respiratory infection prevention.
  • Sodium butyrate (oral): mainly used in research; absorption issue means little reaches the colon where it matters.
  • Saccharomyces cerevisiae fermentate (EpiCor): immune effects in some trials.

Where to actually get postbiotics

  1. Fermented foods: kefir, yoghurt, sauerkraut, kimchi, sourdough, aged cheese. The bacteria's products are present alongside the bacteria themselves.
  2. Bone broth: contains amino acids and peptides relevant to gut barrier.
  3. Diverse fibre intake: feeds your existing bacteria so they produce postbiotics in your colon. Highest use approach.
  4. Supplements: pasteurised Akkermansia (Pendulum, Akesi) and a handful of others. Cost is meaningful; evidence is early.

Common questions

Are postbiotics better than probiotics?
Different, not better. Probiotics deliver live bacteria that interact with your gut. Postbiotics deliver products of fermentation directly. Each has use cases. For most people, eating fermented foods covers both at once.
Should I take a postbiotic supplement?
Probably not as a first step. Diversifying fibre intake to feed your existing bacteria is far cheaper and better-evidenced. Specific postbiotic products (pasteurised Akkermansia for metabolic markers) might be worth considering after that.
Why is butyrate often listed as a postbiotic?
Because gut bacteria produce it from fibre fermentation. Direct oral butyrate supplements are sometimes sold but most absorbs in the small intestine before reaching the colon where it matters. Eating fibre to feed butyrate-producing bacteria is more effective.
Are postbiotics safe?
Generally yes. Because they are inactivated, they avoid the rare safety issues with live probiotics in immunocompromised people. The category is new, so long-term human safety data is still accumulating.

Sources