# Saccharomyces boulardii I-745

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/saccharomyces-boulardii-i-745
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-03
**Evidence Score:** 2 / 10
**Category:** Fermented/Probiotic
**Also Known As:** Saccharomyces boulardii CNCM I-745, S. boulardii I-745, Saccharomyces cerevisiae var. boulardii I-745, S. cerevisiae boulardii CNCM I-745, Boulard's yeast I-745, Probiotic yeast I-745, SB I-745, Lyophilized S. boulardii I-745

## Overview

Saccharomyces boulardii I-745 is a non-pathogenic yeast [probiotic](/ingredients/condition/gut-health) strain whose primary bioactive mechanism involves secreting a 54 kDa serine protease that degrades C. difficile toxins A and B. It colonizes the intestinal lumen transiently, modulating gut microbiota composition and reinforcing epithelial barrier integrity through upregulation of tight-junction proteins.

## Health Benefits

• Reduces antibiotic-associated diarrhea duration and risk (strong evidence from meta-analyses and ESPGHAN guidelines)
• Shortens pediatric acute gastroenteritis by 13.4 hours compared to B. clausii (RCT n=317, P=0.04)
• Prevents recurrent C. difficile infections (recommended by clinical guidelines)
• Reduces H. pylori therapy side effects (guideline-supported)
• Decreases [inflammatory](/ingredients/condition/inflammation) markers IL-6 and TNF-α in sepsis models (animal evidence)

## Mechanism of Action

S. boulardii I-745 secretes a 54 kDa serine protease that proteolytically cleaves C. difficile toxin A receptors on enterocytes and directly degrades toxins A and B, reducing mucosal inflammation. The strain also produces a 120 kDa phosphatase that dephosphorylates and inactivates lipopolysaccharide, dampening NF-κB-mediated [pro-inflammatory cytokine](/ingredients/condition/inflammation) release including TNF-α and IL-8. Additionally, it stimulates secretory IgA production and upregulates expression of tight-junction proteins such as claudin-1 and occludin, restoring intestinal barrier function disrupted by pathogens or antibiotics.

## Clinical Summary

Multiple meta-analyses, including a Cochrane review of over 30 RCTs, demonstrate that S. boulardii I-745 significantly reduces both the incidence and duration of antibiotic-associated diarrhea, with a number needed to treat of approximately 8. ESPGHAN guidelines recommend the strain for managing pediatric acute gastroenteritis, supported by an RCT of 317 children showing it shortens illness duration by 13.4 hours compared to B. clausii (P=0.04). For recurrent Clostridioides difficile infection, clinical guidelines endorse adjunctive use, with trials showing a reduction in recurrence rate from approximately 44.8% to 26.3% when combined with vancomycin or metronidazole. Evidence quality is strong for diarrhea endpoints but more limited for other indications such as IBS and Crohn's disease.

## Nutritional Profile

Saccharomyces boulardii I-745 is a lyophilized probiotic yeast strain, not a traditional food ingredient, so its nutritional profile differs from conventional nutrients. Key compositional data: Protein content approximately 40-45% of dry cell weight (primarily structural and enzymatic proteins including proteases, saccharases, and heat shock proteins). Carbohydrates approximately 35-40% dry weight, dominated by cell wall beta-1,3/1,6-glucans (~30% of cell wall mass) and mannoproteins (~40% of cell wall), with intracellular trehalose serving as a cryoprotectant at ~15-20% of dry weight in lyophilized preparations. Lipids approximately 5-7% dry weight, primarily phospholipids (phosphatidylcholine, phosphatidylethanolamine) and ergosterol (provitamin D2 precursor, ~0.3-0.5% dry weight). Bioactive compounds: Secretory phosphatase (molecular weight ~63 kDa) capable of dephosphorylating bacterial endotoxins LPS and LTA; serine protease (~54 kDa) that cleaves C. difficile toxin A receptors and degrades cholera toxin; polyamines (spermidine, spermine) supporting intestinal epithelial repair. Micronutrient contributions per standard 250 mg capsule dose: B vitamins including thiamine (~0.8 mg equivalent), riboflavin (~0.3 mg), niacin (~3.5 mg), and folate (~15 mcg; bioavailability limited due to yeast matrix). Zinc present at approximately 0.4-0.6 mg per dose bound to metalloproteins. Selenium incorporated at ~2-4 mcg per dose depending on fermentation substrate. Fiber equivalent: [beta-glucan](/ingredients/condition/immune-support)s from cell walls contribute approximately 40-60 mg per 250 mg dose; these are largely indigestible in the upper GI tract, acting as [prebiotic](/ingredients/condition/gut-health)-like substrates but with limited systemic carbohydrate contribution. Caloric contribution is negligible at therapeutic doses (~2-4 kcal per 250 mg capsule). Bioavailability note: S. boulardii I-745 is non-colonizing and transient; it is not absorbed systemically but exerts effects luminally. The lyophilized I-745 strain retains viability at room temperature and survives gastric acid better than many bacterial probiotics due to yeast cell wall architecture, with approximately 10^9 CFU per 250 mg dose reaching the intestinal lumen at ~60-70% viability post-gastric transit.

## Dosage & Preparation

Clinically studied doses range from 250-500 mg (5-10 billion CFU) daily as lyophilized powder in capsules or sachets, typically for 5-7 days. Children often receive 250 mg twice daily. Standardization is to 2.5 x 10^9 CFU per 250 mg dose. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

S. boulardii I-745 is generally well tolerated; the most commonly reported adverse effects are mild bloating and flatulence occurring in a small minority of users. Because it is a live yeast, it is contraindicated in immunocompromised individuals, patients with central venous catheters, and those with known yeast hypersensitivity due to rare but documented cases of fungemia. Concurrent use of oral antifungal agents (e.g., fluconazole, itraconazole) will reduce or eliminate viability of the [probiotic](/ingredients/condition/gut-health) and should be avoided. Safety data in pregnancy are limited to observational studies; use should be discussed with a healthcare provider before administration during pregnancy or lactation.

## Scientific Research

A randomized trial in 317 children with acute diarrhea showed S. boulardii reduced diarrhea duration to 64.6 hours versus 78.0 hours with B. clausii (P=0.04). Over 130 trials exist supporting its use, with meta-analyses and ESPGHAN guidelines recommending it for antibiotic-associated diarrhea prevention. Review context suggests PMID reference PMC10621882.

## Historical & Cultural Context

Isolated in the 1920s by Henri Boulard from Southeast Asian tropical fruits during dysentery outbreaks, S. boulardii became the first yeast [probiotic](/ingredients/condition/gut-health) studied in humans. While lacking deep roots in traditional medicine systems, it has been clinically developed since the 1950s for gastrointestinal disorders.

## Synergistic Combinations

Lactobacillus rhamnosus GG, Prebiotics (FOS/Inulin), Zinc, Glutamine, [Digestive Enzyme](/ingredients/condition/gut-health)s

## Frequently Asked Questions

### What is the recommended dose of Saccharomyces boulardii for antibiotic-associated diarrhea?

Clinical trials supporting prevention of antibiotic-associated diarrhea typically used doses of 250–500 mg (approximately 5–10 billion CFU) taken twice daily, begun within 72 hours of starting antibiotic therapy and continued for the full course plus one week after completion. The I-745 strain specifically has been studied at 250 mg twice daily in pediatric populations and 500 mg twice daily in adults with consistent efficacy outcomes.

### How long does it take for Saccharomyces boulardii to work?

S. boulardii I-745 reaches detectable intestinal concentrations within 3–5 days of consistent dosing, and clinical improvements in diarrhea outcomes are typically observed within 2–4 days of initiation in acute gastroenteritis trials. The strain does not permanently colonize the gut; intestinal levels drop to undetectable within 2–5 days of stopping supplementation, meaning benefits are dependent on continuous intake.

### Can Saccharomyces boulardii be taken with antibiotics at the same time?

Yes, S. boulardii I-745 can be co-administered with antibiotics because, as a yeast, it is inherently resistant to antibacterial agents including amoxicillin, metronidazole, and fluoroquinolones. It should be separated from oral antifungal medications such as fluconazole, which would kill the yeast and negate any benefit. Taking it 2 hours apart from antibiotic doses is a common practical recommendation, though pharmacokinetic resistance makes strict separation less critical than with bacterial probiotics.

### Is Saccharomyces boulardii effective for C. difficile infection?

Evidence supports adjunctive use of S. boulardii I-745 for preventing recurrent C. difficile infection rather than treating primary episodes. A double-blind RCT by Surawicz et al. found that adding S. boulardii to standard antibiotic therapy (vancomycin) reduced recurrence rates from approximately 44.8% to 26.3% in patients with recurrent CDI. The mechanism involves the 54 kDa serine protease degrading toxins A and B, and the strain is endorsed in some clinical guidelines as adjunctive therapy for recurrent cases.

### What is the difference between Saccharomyces boulardii and Saccharomyces cerevisiae?

S. boulardii I-745 and S. cerevisiae (baker's yeast) are closely related at the genomic level—some taxonomists classify S. boulardii as a subspecies of S. cerevisiae—but they differ in key functional properties. S. boulardii I-745 grows optimally at 37°C (human body temperature) rather than 30°C, survives gastric acid passage more effectively, and produces the specific 54 kDa protease and 120 kDa phosphatase responsible for its therapeutic effects, which are not produced by S. cerevisiae baker's strains. These differences make S. boulardii uniquely suited for gastrointestinal probiotic applications.

### Is Saccharomyces boulardii I-745 safe for children and infants?

Saccharomyces boulardii I-745 is well-tolerated in pediatric populations and is recommended by ESPGHAN (European Society of Pediatric Gastroenterology, Hepatology and Nutrition) guidelines for children with acute gastroenteritis and antibiotic-associated diarrhea. Clinical trials have demonstrated safety in infants and young children, though dosing adjustments are typically recommended based on age. Always consult a pediatrician before use in children under 2 years of age.

### Does Saccharomyces boulardii I-745 interact with common medications?

Saccharomyces boulardii I-745 is a non-pathogenic yeast strain with minimal drug interactions; however, it should not be taken simultaneously with antifungal medications as these may inactivate the organism. It can be taken alongside antibiotics (with appropriate spacing), H. pylori triple therapy, and most other medications, though timing separation of 2–4 hours from antifungals is recommended. Consult your healthcare provider if taking immunosuppressants or if you have a central venous catheter, as rare fungemia cases have been reported in critically ill patients.

### What does clinical research show about Saccharomyces boulardii I-745 for acute gastroenteritis?

Meta-analyses and randomized controlled trials demonstrate that Saccharomyces boulardii I-745 significantly shortens the duration of acute gastroenteritis by approximately 13.4 hours compared to B. clausii (P=0.04) in pediatric populations. Evidence supports its use in reducing diarrhea duration and severity across multiple viral and bacterial causes of gastroenteritis. The clinical evidence base qualifies as strong according to systematic reviews and is included in major clinical practice guidelines for gastrointestinal infection management.

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