Postbiotics (heat-killed strains)

About Postbiotics (heat-killed strains)

Preparations of non-viable microbial cells or their components and metabolites — heat-killed lactobacilli, cell wall fragments, bacterial lysates. By definition they contain no living organisms.

Postbiotics solve the two hardest practical problems with probiotics — keeping the organisms alive, and the risk that a living organism poses to a vulnerable person — and in doing so raise an obvious question about how the remaining effect is supposed to work. The answer offered is that immune recognition of bacterial structures does not require the bacterium to be alive, which is biologically reasonable and has some support in small trials of specific heat-killed strains on respiratory symptoms and skin. The literature is young, small and dominated by ingredient suppliers, and the word "postbiotic" is now applied to a very wide range of things.

Sold as

Capsule, Powder, Fermentate, Bacterial lysate

Standardised to

Cells or cell equivalents per dose of a named strain; no living organisms are present — a product without this marker may not resemble what was studied.

Also known as

Paraprobiotics, Tyndallised bacteria, Heat-killed probiotics, Inactivated cultures

Regulation: Sold as a dietary supplement with no pre-market efficacy review. A formal consensus definition of "postbiotic" was published by an international scientific association in 2021, but the term is used loosely in marketing to cover fermentates, metabolites and cell fragments that have very different evidence.

What the research used

The amounts, forms and durations published trials of Postbiotics (heat-killed strains) actually administered.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.