Short answer: CFU count tells you how many live organisms are present, not whether they do anything. Probiotic effects are strain-specific and condition-specific — a higher count of an unstudied strain is worth less than a studied dose of the right one.
Probiotic labels compete on a single number, and it is close to the least useful number on the package.
What CFU actually counts
CFU stands for colony-forming units: the number of viable organisms capable of forming a colony. It is a measure of quantity and viability, and nothing else.
Fifty billion CFU of a strain never tested for your issue is not better than ten billion CFU of one with trial evidence behind it. The count is a volume dial, not a quality signal.
Effects are strain-specific
This is the part the category consistently blurs. Evidence in probiotics attaches to a specific strain, identified by genus, species and strain designation — for example Lacticaseibacillus rhamnosus GG, where ‘GG’ is the strain.
- Findings for one strain do not transfer to another strain of the same species.
- A label giving only genus and species is not telling you enough to match it against any study.
- Multi-strain products are not automatically better; they are simply harder to attribute an effect to.
What to check instead of the count
- Full strain designation for each organism, not just genus and species.
- CFU guaranteed through end of shelf life, not just at time of manufacture — these differ substantially.
- Storage requirements. Some strains need refrigeration; viability falls if they are not kept properly.
- Evidence for your actual reason for taking it, since a strain studied for antibiotic-associated diarrhoea may have nothing behind it for bloating.
The intervention with better evidence
For most people not treating a specific condition, increasing dietary fibre has a stronger and more consistent evidence base for gut health than any probiotic capsule — and it feeds the organisms already present rather than adding transient ones.
Probiotics are also not risk-free for everyone: people who are severely immunocompromised or critically ill should not take them without medical advice.
Frequently asked questions
Is a higher CFU count better?
Not by itself. The count matters only in the context of a strain with evidence for the outcome you care about, at a dose comparable to the studies.
Do I need to refrigerate probiotics?
It depends on the strain and formulation. Follow the label — viability drops if storage requirements are not met, regardless of the printed count.
Are multi-strain probiotics better than single-strain?
Not necessarily. More strains means more variables and weaker attribution. What matters is whether the specific strains have evidence for your purpose.
Sources
- National Center for Complementary and Integrative Health — Probiotics: What You Need To Know.
Medical disclaimer. This article is general information, not medical advice, and cannot account for your history, medication or symptoms. Speak to a doctor or pharmacist before starting any supplement. Read our full disclaimer.