Probiotics That Actually Do Something: A Strain-by-Strain Guide

The probiotic aisle is a case study in marketing outrunning science. Two products can both say 'Lactobacillus acidophilus, 20 billion CFU' and behave completely differently in the body — because a strain (say, L. acidophilus NCFM) is what has clinical evidence, not the species. Here's how to read a label and pick strains that are actually studied for what you're trying to fix.

For bloating and IBS

• Bifidobacterium infantis 35624 — the strongest RCT data for IBS symptom relief.
• Lactobacillus plantarum 299v — reduces bloating and abdominal pain in multiple trials.
• Saccharomyces boulardii CNCM I-745 — a beneficial yeast, useful post-antibiotic and for traveler's diarrhea.

For immune support

• Lactobacillus rhamnosus GG — the most studied probiotic in existence; solid data for upper respiratory infections.
• Bifidobacterium lactis Bi-07 — reduces cold and flu incidence in office-worker populations.

For mood and the gut-brain axis

Emerging RCTs point at a handful of 'psychobiotics' with real effect sizes on anxiety and depressive symptoms in mild-to-moderate populations. Lactobacillus helveticus R0052 combined with Bifidobacterium longum R0175 is the most-replicated pairing so far.

How to actually take them

• Start after a course of antibiotics, then continue for at least 30 days.
• Take with food — a small amount of fat protects the strains through stomach acid.
• Refrigerate unless the label specifies shelf-stable strains (spore-formers like Bacillus coagulans don't need refrigeration).
• Pair with prebiotic fiber (partially-hydrolyzed guar gum, PHGG, is best tolerated) to feed the strains once they land.