Gut Health & Digestive
Saccharomyces Boulardii
Also known as: Florastor · S. boulardii lyo · Saccharomyces cerevisiae var. boulardii
A probiotic yeast (not bacterium) with the strongest evidence of any single probiotic strain for preventing antibiotic-associated diarrhoea and traveller's diarrhoea. Unaffected by antibiotics.
Effective Dose
250–500mg (5–10 billion CFU) / day
per clinical evidence
Evidence Level
Strong
Gut Health & Digestive
Mechanism
Probiotic yeast — C. difficile toxin binding, secretory IgA stimulation, gut pH reduction
primary action
Best For
Traveller's diarrhoea
Antibiotic-associated diarrhoea, C. difficile prevention, IBS
This profile is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications.
What Is Saccharomyces Boulardii?
Saccharomyces boulardii is a non-pathogenic yeast first isolated from lychee and mangosteen by Henri Boulard in 1923. As a yeast, it is completely unaffected by antibacterial antibiotics — making it uniquely valuable during and after antibiotic therapy. It has the broadest and most robust evidence base of any single probiotic strain.
How It Works: The Science
S. boulardii directly binds and neutralises C. difficile toxins A and B (via a serine protease). It secretes a protease that cleaves receptors used by pathogenic bacteria (Salmonella, C. difficile) to adhere to gut epithelium. It stimulates secretory IgA, reinforces tight junctions, and releases polyamines that trophically support enterocytes.
Primary Mechanism
Probiotic yeast — C. difficile toxin binding, secretory IgA stimulation, gut pH reduction
Evidence-Based Benefits
Dosage Guide
Effective Dose
250–500mg (5–10 billion CFU) / day
250–500mg (5–10 billion CFU) once or twice daily. Start at the beginning of an antibiotic course and continue 2–4 weeks after completion. Can be taken simultaneously with antibiotics (yeast — antibiotic-resistant).
Safety Profile & Side Effects
Avoid in severely immunocompromised individuals or those with central venous catheters (rare risk of fungaemia). Otherwise extremely safe — no systemic adverse effects in healthy users.
Who Should (and Shouldn't) Take It
Everyone taking antibiotics (mandatory companion), international travellers, those with recurrent C. difficile, and IBS patients. The single most evidence-backed probiotic strain for acute situations.
Frequently Asked Questions
Related Ingredients
Medical Disclaimer
Ingredient profiles are for informational purposes only and do not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications. Full disclaimer →