Probiotic Glossary
Definitions built around what terms mean clinically, not how brands use them in marketing.
AFU (Active Fluorescent Units)
AFU (Active Fluorescent Units) is an alternative measure of probiotic potency that counts both colony-forming and dormant-but-viable bacteria using flow cytometry. Used by Seed DS-01.
CFU (Colony Forming Units)
CFU (Colony Forming Units) is the standard measure of probiotic potency — but higher CFU does not mean better clinical outcomes. Strain identity and matched-indication evidence are what drive results.
Lactobacillus
Lactobacillus is one of the most common genera of probiotic bacteria. The genus contains hundreds of species — and within each species, hundreds of strains. Clinical evidence is strain-specific, not genus-wide.
Postbiotics
Postbiotics are the metabolic byproducts of probiotic bacteria — including short-chain fatty acids, enzymes, and cell wall components. They are the newest category in gut supplement science, with an emerging (but not yet definitive) evidence base.
Prebiotics
Prebiotics are non-digestible fibres that selectively feed beneficial gut bacteria. They are distinct from probiotics (live bacteria) and are increasingly combined with probiotics in synbiotic formulations.