Probiotics and Bowel Regularity: Strains, CFU & Evidence
Probiotics are not one ingredient. They are live microorganisms identified by genus, species and often strain, and their effects can differ substantially.
Reviewed September 2026. This page is educational, not medical advice.
Strain is part of the product identity
Two strains from the same species can have different evidence. A label that stops at genus/species gives less information than one that identifies the strain used in relevant research.
CFU is not the whole story
Colony-forming units describe viable organisms, but timing matters. A claim “at manufacture” is different from a guarantee through the end of shelf life.
Constipation evidence
Meta-analytic evidence suggests some probiotic interventions may improve stool frequency, but study results are heterogeneous. The correct buyer question is “which strain, for whom, at what dose?”