Probiotics: the live microbes
Probiotics are live microorganisms that, when consumed in adequate amounts, confer a health benefit. The key word is live: the strain must survive to the gut.
Effects are strain-specific. Two strains of the same species are not interchangeable, which is why compliant labels name the strain, not just the genus.
Prebiotics: the food
Prebiotics are ingredients selectively used by beneficial gut microbes, such as oligofructose or inulin. They are not alive; they feed rather than colonise.
Postbiotics: the output
Postbiotics are metabolites or structural components produced by probiotics — short-chain fatty acids, exopolysaccharides, peptides. They contain no live cells, so storage requirements differ completely from probiotic products.
Dietary fibre: a chemical category
Dietary fibre is the umbrella term for carbohydrates that resist digestion in the small intestine. Some fibres are prebiotic, but not all: the test is whether beneficial microbes selectively use them.
Frequently asked
- Does a fermented juice contain all four?
- It depends on raw material and process. Fruit and vegetable bases contain fibre; fermentation consumes sugar and produces acids and metabolites; whether live cells remain depends on whether the product is pasteurised.
- Can the terms be used interchangeably?
- No. They refer to live cells, their substrate, their metabolites and an indigestible carbohydrate class — different mechanisms and different labelling rules.