Probiotic CFU

A probiotic supplement labelled '50 billion CFU' makes a claim that must remain true at the end of shelf life under the labelled storage condition, not on the day of release. The category combines a fragile biological active with progressive die-off, strain-level specificity required for any health-related claim (the WHO/FAO Joint Expert Consultation and consensus literature emphasise that probiotic efficacy is strain-specific, not species-specific), and a supply chain in which mislabelling, strain substitution and CFU shortfall have been repeatedly demonstrated by independent third-party testing.

Strain identity has consolidated on whole-genome sequencing as the reference standard, with strain deposit numbers (ATCC, DSMZ, NCIMB, LMG) on every specification and WGS-verified incoming-lot identity as the operating norm; this also supports EFSA QPS (Qualified Presumption of Safety) listing and antimicrobial-resistance gene screening. Enumeration is performed by serial dilution and plating on strain-appropriate selective media per USP <2055> and related compendia, or increasingly by flow cytometry with viability staining per ISO 19344 (reported as Active Fluorescent Units, AFU). Inter-laboratory disagreement is driven by media variants, incubation atmosphere and time, and matrix recovery; the label method must be specified and switching mid-lifecycle requires bridging studies.

Overage — the headroom between release count and label claim — is set from stability data, not from a generic table. Water activity is the dominant driver of ambient die-off: dry capsules at aw < 0.25 typically retain CFU through 24 months, gummies at aw 0.5-0.7 are largely incompatible with conventional probiotics without spore-forming strains or specialised encapsulation. Packaging (moisture barrier, integrated desiccant, nitrogen flush) and storage condition labelling (refrigerated vs ambient) directly extend or compress shelf life. ICH Q1A(R2)-aligned stability programmes track CFU at 0, 3, 6, 9, 12, 18, 24 and 36 months at the labelled condition, with the controlling specification at end of shelf life. FDA, Health Canada, EFSA and IPA Best Practices all converge on end-of-shelf-life labelling — 'at time of manufacture' labelling without disclosure is targeted by both regulators and class-action litigation.