Last verified: 46 days ago
Saccharomyces Boulardii
Also known as: S. boulardii, Saccharomyces boulardii CNCM I-745, probiotic yeast, Sb
Evidence under review. — Not yet rated
Probiotic yeast with solid evidence for reducing gut infection recurrence and antibiotic side effects.
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What it does
Saccharomyces boulardii is a beneficial yeast used as a probiotic supplement. It has the strongest evidence for reducing recurrence of Clostridioides difficile gut infections when added to...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
250–500 mg daily based on study doses
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Found in
What the Science Says
Saccharomyces boulardii is a beneficial yeast used as a probiotic supplement. It has the strongest evidence for reducing recurrence of Clostridioides difficile gut infections when added to antibiotic treatment, and for cutting side effects like diarrhea and nausea during H. pylori eradication therapy. It also shows promise for helping children with acute gastroenteritis and for supporting gut health in people on long-term acid-suppressing medications.
What It Doesn't Do
Won't boost athletic or anaerobic performance — a clinical trial found zero effect on sprint power. Not proven to consistently prevent radiation-induced diarrhea in cancer patients. No evidence it works as a standalone treatment for serious infections. The engineered 'next-gen' versions that deliver drugs or fight Listeria are lab research only — not available in any supplement.
Evidence-Based Benefits
S. boulardii shows moderate evidence as an adjunct therapy for reducing recurrence of Clostridioides difficile infection (CDI) when combined with vancomycin — global cure rate 96.6% vs 85.3% placebo, recurrence 1.7% vs 13.1% (PMID: 40457042). It also demonstrates benefit in reducing adverse events and potentially improving eradication effectiveness when added to H. pylori concomitant therapy in real-world European practice (PMID: 41923280). In combination with smectite for pediatric acute gastroenteritis, a meta-analysis of 57 RCTs found improved outcomes (PMID: 41798274), and it showed benefit for SIBO eradication when combined with rifaximin (PMID: 40884341).
Moderate EvidenceEffective at: 250-500 mg daily (clinical trials); No universally established dose across all indications
Source: auto-research
Absorption & Bioavailability
Unknown for systemic absorption — S. boulardii acts locally in the gut and does not colonize permanently. It is naturally resistant to antibiotics due to its eukaryotic nature, which is a practical advantage when taken alongside antibiotic therapy.
Red Flags to Watch For
- Immunocompromised individuals (e.g., ICU patients, those with central venous catheters) face rare but serious risk of fungemia — consult a doctor before use
- Results for radiation-induced diarrhea were inconsistent in one RCT, with the treatment group actually experiencing more diarrhea at week 4 than placebo
- Most benefits are condition-specific (C. diff recurrence, H. pylori therapy) — broad 'gut health' marketing overstates the evidence
- Synbiotic products often combine S. boulardii with multiple other strains, making it impossible to attribute effects to S. boulardii alone
Products Containing Saccharomyces Boulardii
See how Saccharomyces Boulardii is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06