How to Choose a Probiotic Strain
A full probiotic designation has three parts: genus, species and strain, as in Lactobacillus rhamnosus GG. Research is conducted on specific strains and does not transfer automatically between strains of the same species, so a label naming only genus and species tells you less than it appears to.
Probiotic research is conducted on specific strains, and the findings do not transfer automatically between strains of the same species. Reading a probiotic label means reading three levels of name, not one.
Genus, species, strain
A complete designation looks like Lacticaseibacillus rhamnosus GG, or Bifidobacterium animalis subsp. lactis BB-12. The three parts are:
- Genus — Lactobacillus, Bifidobacterium, Saccharomyces and so on.
- Species — the second Latin word.
- Strain — the alphanumeric code at the end, which identifies the specific isolate.
A label giving only genus and species is telling you less than it appears to. The strain code is the part that ties a product to published research.
Renamed genera
Several familiar Lactobacillus species were reclassified into new genera in a 2020 taxonomic revision, which is why you may see the same organism under two names on different products — Lactobacillus casei and Lacticaseibacillus casei, for instance. The organism has not changed; the naming has.
Single strain or multi-strain
Products range from one named strain to a dozen or more. A longer list is not automatically better: the useful question is whether the panel states the CFU count for each strain, or only a combined total. Where only a total is given, you cannot tell whether a strain of interest is present in a meaningful amount or as a token addition.
Matching a product to research
If you have read about a particular strain, look for that strain code on the label. Where a product names the strain and the dose, you can compare it against what was studied. Where it names only a species, you cannot.
What we will not tell you
Which strain to take for a particular purpose is a clinical question rather than a labelling one, and it is not one this site answers. What we can do is help you see what a bottle actually contains. If you are choosing a probiotic for a specific reason, a pharmacist or dietitian is the right person to ask.
See also what CFU means and our probiotic comparison.
References
- NIH Office of Dietary Supplements — Probiotics (Health Professional Fact Sheet)
- NCCIH — Probiotics: What You Need To Know