Saccharomyces boulardii — The Probiotic Yeast
Saccharomyces boulardii is a non-pathogenic, transient probiotic yeast widely used to support gastrointestinal health and prevent dysbiosis. While its direct impact on human longevity is unproven, its ability to reduce systemic inflammation via gut microbiome modulation and protect against age-related intestinal permeability makes it relevant to healthspan preservation.
Mechanism of Action
Saccharomyces boulardii exerts its effects primarily within the gastrointestinal tract by modulating local immune responses and maintaining gut barrier integrity. It inhibits the production of pro-inflammatory cytokines by blocking the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK). Additionally, S. boulardii activates the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ), which protects against gut inflammation. It also secretes proteases that degrade bacterial toxins and produces short-chain fatty acids that nourish colonocytes.
Human Trial Evidence
No published human longevity trials. Clinical evidence in humans is primarily focused on gastrointestinal health, where it has been shown to prevent antibiotic-associated diarrhea and Clostridium difficile infections. Recent small-scale trials have explored its effects on weight loss and body composition in obese adults when combined with superoxide dismutase, but long-term healthspan data is lacking.
Dosing Protocol
250–500 mg (typically 5–10 billion CFU) taken 1–2 times daily is the standard dose in clinical practice. It is typically taken orally, with or without food. It does not require refrigeration but should be kept away from extreme heat. As a yeast, it is naturally resistant to antibacterial antibiotics and can be taken concurrently with them.
Safety & Contraindications
Generally well-tolerated in healthy individuals. The most common adverse effect is mild constipation or increased flatulence. It is contraindicated in critically ill, immunocompromised patients, or those with central venous catheters due to a rare but severe risk of fungemia (fungal bloodstream infection). It should not be taken with systemic antifungal medications, which will inactivate the yeast.