Probiotics: you choose a strain, not a jar

The name on the jar has three parts: genus, species and strain. In Lacticaseibacillus rhamnosus GG, those last letters are the strain. Evidence is collected at the strain level, which is why the letters matter.

Where the evidence is stronger

Cochrane reviews and clinical guidelines most often mention probiotics in two situations: preventing antibiotic-associated diarrhoea (especially Saccharomyces boulardii and L. rhamnosus GG), and shortening acute infectious diarrhoea. There are many trials here, though results vary.

Where the data thin out

Irritable bowel syndrome, skin, mood and weight are all active areas of research, but the conclusions stay cautious: different strains, different doses, short follow-up.

Reading the label

• The full strain name, not just the genus.
• CFU counts at the end of shelf life, not at the date of manufacture.
• Storage conditions — some strains need refrigeration.
• A stated purpose: a serious manufacturer names the strain and what it was studied for.

A caution

For people who are severely immunocompromised, have a central venous catheter or are critically ill, probiotics are a decision for a doctor. Cases of fungaemia and bacteraemia have been reported.