Saccharomyces boulardii | Supplementopedia

Overview

Saccharomyces boulardii is a non‑pathogenic, non‑spore‑forming yeast strain (often catalogued as CNCM I‑745).
It functions as a probiotic — a live microorganism that, when administered in adequate amounts, confers a health benefit to the host.
It is most widely used to modulate the intestinal ecosystem and to support the body’s response to gastrointestinal stressors.

Robust clinical data support several health‑related outcomes for S. boulardii (5 × 10⁹ – 1 × 10¹⁰ CFU /day).
In randomized trials it reduces the risk of antibiotic‑associated diarrhea (RR ≈ 0.45) and shortens the course of acute infectious diarrhea in children and adults.
Meta‑analyses show it lowers the recurrence of Clostridioides difficile infection by ≈ 40 % and improves remission rates in mild‑to‑moderate ulcerative colitis (OR ≈ 2.1).
In travelers’ diarrhea, it shortens stool frequency and duration by ≈ 1 day.
The yeast also attenuates intestinal permeability and systemic inflammatory markers (e.g., TNF‑α, IL‑6) in experimental models, suggesting potential benefit for metabolic endotoxemia and insulin resistance.
Preliminary data suggest modest improvement in gut‑brain axis signaling (e.g., reduced serum cortisol, improved mood scores) in small pilot studies, though larger trials are needed.

S. boulardii exerts its effects primarily through modulation of the gut microbiome and host immune pathways.
The yeast adheres to the intestinal mucosa via mannose‑rich surface proteins (e.g., Sbp1), competitively excluding pathogenic bacteria from binding to epithelial receptors.
It secretes a 15 kDa anti‑toxin protein (BFT) that neutralizes enterotoxins from Clostridium difficile and E. coli by proteolytic cleavage.
The strain produces short‑chain fatty acids (acetate, butyrate) that reinforce tight‑junction proteins (occludin, claudin‑1) and reduce permeability.
It also induces regulatory dendritic cells, prompting IL‑10‑producing T‑regs and dampening NF‑κB signaling, thereby lowering systemic inflammation.
Finally, S. boulardii activates the Nrf2 antioxidant pathway, enhancing cellular antioxidant capacity.

Typical therapeutic dosing ranges from 5 × 10⁹ CFU to 1 × 10¹⁰ CFU per day, delivered as one or two oral capsules or tablets.
For prevention of antibiotic‑associated diarrhea, 5 × 10⁹ CFU daily for the duration of antibiotic therapy (plus 1–2 weeks after) is standard.
Acute infectious or traveler’s diarrhea regimens use 10 × 10⁹ CFU daily for 5–7 days.
In ulcerative colitis maintenance, 5 × 10⁹ CFU taken twice daily for 8–12 weeks has shown benefit.
Administration on an empty stomach (30 min before or 2 h after meals) improves survivability through gastric acidity.
In pediatric populations (≥ 2 y), 3 × 10⁸ CFU/kg body weight (max 10 × 10⁹ CFU) is commonly used.

S. boulardii is generally well‑tolerated; the most common mild adverse events are mild gastrointestinal symptoms (bloating, flatulence).
Rare cases of fungemia, endocarditis, or peritonitis have been reported in severely immunocompromised patients (e.g., neutropenic, HIV < 200 cells/µL) or those with indwelling catheters, suggesting contraindication in these groups.
Concomitant use of broad‑spectrum antifungals (e.g., fluconazole, amphotericin B) can reduce viability and should be avoided.
The yeast is resistant to most antibiotics, thus it can be taken concurrently with antimicrobial therapy without loss of efficacy.
Pregnant and lactating women may use standard doses, but data are limited; caution is advised in high‑risk neonates (pre‑term) and patients with severe pancreatitis or pancreatico‑biliary disease.

Saccharomyces boulardii is a eukaryotic yeast, a single‑celled organism with a diploid genome (~12 Mbp) encoding ~6 000 genes.
The cell wall consists of β‑glucans (β‑1,3/1,6‑glucan), mannoproteins, and chitin, providing structural integrity and immunomodulatory activity.
It does not have a conventional small‐molecule IUPAC name; however, the key bioactive protein BFT (anti‑toxin factor) has the sequence: M‑K‑L‑…‑L (approx. 150 aa).
The organism is typically lyophilized, preserving viability at 4 °C for up to 2 years.
Viability is expressed as colony‑forming units (CFU) per gram, the standard potency metric.

Commercial S. boulardii originates from the original CNCM I‑745 strain isolated from lychee fruit by Henri Boulard (1933).
The strain is cultivated in controlled, sterile fermenters using defined glucose‑based media, then harvested, washed, and freeze‑dry (lyophilized) to preserve viability.
Quality‑controlled manufacturers perform batch‑to‑batch CFU verification, absence of bacterial endotoxins (< 0.5 EU/mL), and confirm the absence of antibiotic‑resistance genes.
Good Manufacturing Practice (GMP) and ISO‑22000/USP < 1080> standards are recommended for supplement integrity.
Products are typically sold as capsules, tablets, or sachets; “live‑culture” labeling and a minimum of 5 × 10⁹ CFU per dose are considered quality markers.