Probiotics: Which Ones Actually Have Evidence?
Not all probiotics are equal. Here are the specific strains with real evidence, and the ones you’re paying for a marketing story.
Medically reviewed by Dr. Sarah Mitchell, ND
Naturopathic doctor, Vancouver BC
Written by UnityLife Admin
Updated April 2026 · Reviewed March 2026
Probiotics are strain-specific. “Lactobacillus” on a label tells you almost nothing about what the product will do. Here are the few strains with actual human RCTs behind them.
Strains with the best evidence
Saccharomyces boulardii — prevents antibiotic-associated diarrhoea.
Lactobacillus rhamnosus GG — reduces duration of acute childhood diarrhoea.
Bifidobacterium infantis 35624 — modest evidence in IBS.
Strains oversold in Canadian stores
Generic “50 billion CFU multi-strain” blends rarely have published RCTs on the specific combination you’re buying.
The bottom line
Before spending, match your reason (antibiotics, IBS, traveller’s diarrhoea) to a specific research-backed strain. Otherwise you’re paying for marketing.
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The bottom line
Before spending, match your reason (antibiotics, IBS, traveller’s diarrhoea) to a specific research-backed strain. Otherwise you’re paying for marketing.
Frequently asked questions
S. boulardii reduces antibiotic-associated diarrhoea risk. Most generic probiotics don’t.
Sources & further reading
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