What does Saccharomyces Boulardii do?

Probiotic yeast with solid evidence for reducing gut infection recurrence and antibiotic side effects.

Is Saccharomyces Boulardii safe?

Immunocompromised individuals (e.g., ICU patients, those with central venous catheters) face rare but serious risk of fungemia — consult a doctor before use

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Saccharomyces Boulardii

Also known as: S. boulardii, Saccharomyces boulardii CNCM I-745, probiotic yeast, Sb

Effective Dosage

250–500 mg daily based on study doses

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 Evidence

Effective 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

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