Saccharomyces boulardii CNCM I-745

Tier 1 — strong evidence · Gut health · Antibiotic-associated diarrhoea · C. diff prevention

The CNCM I-745 designation identifies the specific, deposited strain behind most published S. boulardii trials — not a generic yeast. Being a eukaryote, it is intrinsically resistant to all antibacterial antibiotics, allowing co-administration from day one of any antibiotic course. Multiple meta-analyses confirm it reduces antibiotic-associated diarrhoea (AAD) risk by roughly 50% (Pillai Cochrane 2008, PMID 18254055; Waitzberg 2024 narrative review, PMID 38286962); one placebo-controlled RCT found S. boulardii halved C. difficile recurrence (RR 0.59). Guarino 2015 review (PMID 26447963)…

Dose: 250–500 mg (approximately 5–10 billion CFU) twice daily. Begin at antibiotic day 1 (or within 48 hours) and continue for 1 week after completing the antibiotic course.