Saccharomyces boulardii Does NOT Help with Yeast Overgrowth in the GI Tract
Saccharomyces boulardii is itself a yeast organism and will not treat or prevent colonization by other pathogenic yeasts like Candida species in the gastrointestinal tract. In fact, animal studies demonstrate that S. boulardii administration does not prevent subsequent GI colonization by Candida albicans 1.
Why S. boulardii Cannot Treat Yeast Overgrowth
S. boulardii is a Yeast, Not an Anti-Fungal Agent
S. boulardii is a strain of Saccharomyces cerevisiae, meaning it is itself a fungal organism that colonizes the GI tract temporarily 1.
In experimental models, mice given S. boulardii for 2-4 weeks showed no reduction in Candida albicans GI colonization when subsequently exposed to Candida-containing feed 1.
Gut colonization by S. boulardii is proportional to the administered dose but lasts only approximately 1 week after discontinuation, with no protective effect against other yeast species 1.
Evidence-Based Indications for S. boulardii
The American Gastroenterological Association conditionally recommends S. boulardii specifically for preventing Clostridioides difficile infection in patients on antibiotics (RR 0.41; 95% CI 0.22-0.79), not for yeast overgrowth 2, 3.
The mechanism by which S. boulardii protects against C. difficile is that antibiotics do not kill yeast, allowing S. boulardii to survive concurrent antibiotic exposure and colonize disrupted gut niches that opportunistic bacterial pathogens would otherwise exploit 2, 3.
This same property means S. boulardii will not be eliminated by antibiotics that might otherwise suppress bacterial flora and allow yeast overgrowth 2.
Critical Safety Concern: Risk of Fungemia
S. boulardii is absolutely contraindicated in immunocompromised patients due to risk of fungemia or systemic yeast infection 3, 4.
Case reports document fungemia following S. boulardii probiotic treatment, particularly in elderly or debilitated patients 5.
Patients with severe underlying illnesses should avoid S. boulardii due to potential harms outweighing benefits 3.
What S. boulardii Does NOT Treat
The American Gastroenterological Association makes no recommendation for S. boulardii in irritable bowel syndrome, with three studies involving 232 adults finding no difference between S. boulardii and placebo for abdominal pain (standardized MD 0.26; 95% CI -0.09 to 0.61) 2, 3.
S. boulardii is not recommended for bloating or distention 3.
The American Gastroenterological Association suggests against probiotics including S. boulardii in children with acute infectious gastroenteritis 3.
Clinical Bottom Line
If you suspect pathogenic yeast overgrowth (such as Candida species) in the GI tract, S. boulardii is not an appropriate therapeutic intervention and may theoretically worsen the fungal burden 1. Consider antifungal therapy instead, based on clinical presentation and diagnostic confirmation.