Saccharomyces Boulardii
Saccharomyces boulardii
TL;DR
S. boulardii is a yeast, not a bacterium, which is why it survives antibiotics. It has the strongest probiotic evidence base for preventing antibiotic-associated diarrhoea and for travellers' diarrhoea.
Ideal For
- Preventing antibiotic-associated diarrhoea
- Travellers' diarrhoea prophylaxis
- Paediatric acute gastroenteritis
- Recovery of digestive function after gut infection
Avoid If
- Immunocompromised or critically ill
- Central venous catheter in place
- Yeast allergy
- Active Clostridioides difficile infection as sole treatment
Frequently Asked Questions
Can I take it with my antibiotic?
How long after antibiotics should I continue?
Does it treat C. difficile?
Who should not take it?
Overview
Most probiotics are bacteria and are therefore killed by the antibiotics they are meant to protect against — S. boulardii is a yeast, intrinsically resistant to antibacterial agents, and this single fact explains most of its clinical niche. Meta-analyses and Cochrane reviews consistently show it reduces the incidence of antibiotic-associated diarrhoea by roughly half, with a number needed to treat in the region of ten, and it has supporting evidence in paediatric acute gastroenteritis, where it shortens diarrhoea duration by about a day, and in travellers' diarrhoea. Evidence for preventing recurrence of Clostridioides difficile infection is more mixed, and it should not be considered a treatment for active C. difficile. Mechanistically it does several distinct things: it secretes a protease that degrades C. difficile toxin A and its receptor, it produces a phosphatase that inactivates E. coli endotoxin, it stimulates secretory IgA, and it supports enterocyte brush border enzyme activity. It does not colonise — it clears within days of stopping, so it must be taken throughout the antibiotic course and for a period afterwards. The one important safety limit is fungaemia, reported in critically ill and immunocompromised patients and in those with central venous catheters, which makes it inappropriate in intensive care settings.
How It Works
- A yeast, so intrinsically resistant to antibacterial antibiotics
- Secretes a protease that degrades C. difficile toxin A
- Neutralises E. coli endotoxin via a phosphatase
- Transient — clears within days of stopping
Quick Facts
- A yeast — antibiotics do not kill it
- Roughly halves antibiotic-associated diarrhoea risk
- Does not colonise; stop and it is gone within days
- Contraindicated in critical illness and central lines
Benefits & Outcomes
Fungal Infection Resistance
Better evidence than most antifungal botanicals, particularly around antibiotic use.
Candida Control
S. boulardii is the best-supported option for limiting Candida overgrowth, particularly around antibiotic courses.
Diarrhea Prevention
S. boulardii roughly halves the risk of antibiotic-associated diarrhoea and is the best-studied single organism for this purpose.
Microbiome Diversity Enhancement
S. boulardii is a beneficial yeast with strong evidence for protecting gut ecology during antibiotic courses — antibiotics do not kill it.
Health Concerns Addressed
Frequent Diarrhea
The strongest probiotic evidence in the field. S. boulardii roughly halves the risk of antibiotic-associated diarrhoea and shortens infectious diarrhoea by about a day.
Intestinal Parasites
A possible add-on to prescribed antiparasitic drugs for protozoal infections, with small, mostly positive but inconsistent trials and no reliable evidence for worms.
Supporting Research17 studies
Clinical efficacy of Saccharomyces boulardii and metronidazole compared to metronidazole alone in children with acute bloody diarrhea caused by amebiasis: a prospective, randomized, open label study
Dinleyici EC, Eren M, Yargic ZA +2 more
significantly decreases duration of (bloody) diarrhea and enhances clearance of cysts
Efficacy and safety of Saccharomyces boulardii in amebiasis-associated diarrhea in children
Savaş-Erdeve S, Gökay S, Dallar Y
does not seem to be more effective than metronidazole treatment alone
Efficacy of saccharomyces boulardii with antibiotics in acute amoebiasis
Mansour-Ghanaei F, Dehbashi N, Yazdanparast K +1 more
seems to decrease the duration of clinical symptoms and cyst passage
Saccharomyces boulardii and infection due to Giardia lamblia
Besirbellioglu BA, Ulcay A, Can M +4 more
S. boulardii may be effective in treating giardiasis when combined with metronidazole therapy
Clinical efficacy of Saccharomyces boulardii or metronidazole in symptomatic children with Blastocystis hominis infection
Dinleyici EC, Eren M, Dogan N +3 more
Metronidazole or S. boulardii has potential beneficial effects in B. hominis infection
Fungemia and Other Fungal Infections Associated with Use of Saccharomyces boulardii Probiotic Supplements
Rannikko J, Holmberg V, Karppelin M +4 more
the odds ratio for use of an S. boulardii probiotic was 14
Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea
Szajewska H, Kolodziej M
Saccharomyces boulardii reduced the risk of antibiotic-associated diarrhoea from about 19 percent to 8.5 percent across 21 randomised trials in children and adults.
The impact of probiotics on Helicobacter pylori eradication with bismuth quadruple therapy: A systematic review and meta-analysis.
Liu YH, Zhang J, Li DH +1 more
PBQT significantly improved H. pylori eradication rates compared to BQT alone (pooled odds ratio [OR] = 1.49, 95% confidence interval [CI] 1.20-1.85; P = 0.0004), with low heterogeneity (I² = 0%).
Prophylactic Saccharomyces boulardii versus nystatin for the prevention of fungal colonization and invasive fungal infection in premature infants
Saccharomyces boulardii was compared with nystatin for prevention of fungal colonization and invasive fungal infection in premature infants.
Probiotics for vulvovaginal candidiasis in non-pregnant women
Xie HY, Feng D, Wei DM
Probiotic adjuncts, including yeast and lactobacillus preparations, showed low-certainty benefit in candidiasis.
Systematic review and meta-analysis of Saccharomyces boulardii in adult patients
McFarland LV
Across 31 randomised trials S. boulardii was significantly protective for antibiotic-associated diarrhoea, travellers diarrhoea and Clostridioides difficile recurrence.
The effect of Saccharomyces boulardii supplementation on Helicobacter pylori eradication in children: a systematic review and meta-analysis of randomized controlled trials.
Liu LH, Han B, Tao J +1 more
S. boulardii in combination with STT was more effective than STT alone (intention-to-treat analysis: 87.7% vs. 75.9%, RR = 1.14, 95% CI: 1.10-1.19, P < 0.00001).
Saccharomyces boulardii as a Probiotic Supplement in Helicobacter pylori Eradication Therapy: A Meta-analysis
Westphal JR, Koch N, Vilchez-Vargas R +1 more
The supplementation of S. boulardii to H. pylori therapy caused a significant increase in overall eradication rates and a significant decrease in overall diarrhea, nausea, and epigastric pain rates.
Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Outpatients: A Systematic Review and Meta-Analysis
Blaabjerg S, Artzi DM, Aabenhus R
Probiotics including S. boulardii reduced antibiotic-associated diarrhoea in outpatients, with a number needed to treat around 13.
Systematic Review and Meta-Analysis: Safety and Efficacy of Saccharomyces boulardii for Prevention of Clostridioides difficile Infection
Tariq R, Tahir MW, Hayat M +2 more
Pooled trials showed no statistically significant reduction in primary Clostridioides difficile infection with S. boulardii.
Efficacy and safety of the probiotic Saccharomyces boulardii for the prevention and therapy of gastrointestinal disorders
Kelesidis T, Pothoulakis C
Rare fungemia reported almost exclusively in critically ill or catheterised patients.
Cytokine and clinical response to Saccharomyces boulardii therapy in diarrhea-dominant irritable bowel syndrome: a randomized trial
Abbas Z, Yakoob J, Jafri W +5 more
S. boulardii improved quality of life scores and reduced pro-inflammatory cytokines in diarrhoea-predominant IBS.
Safety Information
Potential Side Effects
Usually mild: bloating, flatulence, constipation and thirst. The serious concern is fungaemia, which has occurred in critically ill patients, those with central lines and the severely immunocompromised.
Contraindications
Immunocompromise, critical illness, central venous catheters and yeast allergy. Healthcare staff should avoid opening capsules near catheterised patients, as environmental contamination has caused fungaemia in adjacent patients.
Drug Interactions
- Antifungals (fluconazole, nystatin) — will kill the yeast; separate or avoid
- Antibacterial antibiotics — no interaction, which is the point
- Immunosuppressants — increases fungaemia risk
Pregnancy & Breastfeeding
Pregnancy: Likely safe
Breastfeeding: Likely safe
Dosage Guidelines
Dosage Used in Studies
250-1000 mg
Best Time to Take
Twice daily; can be taken at the same time as antibiotics
Best Form
S. boulardii CNCM I-745 or comparable characterised strain
Bioavailability
Not absorbed; acts within the gut lumen and clears within two to five days of stopping.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| Travellers' diarrhoea | 250-500 mg daily starting 5 days before travel | |
| Paediatric gastroenteritis | 250 mg twice daily for 5-7 days | |
| Antibiotic-associated diarrhoea | 500 mg twice daily, starting with the antibiotic and continuing 1-2 weeks after it finishes | |
| Timing | Can be co-administered with antibiotics — no need to separate |
Forms Compared
Lyophilised capsules
250-500 mg (about 5-10 billion CFU) twice daily; the trial form
Sachets
Useful for children; mix with cool liquid only
Combination products
Often paired with lactobacilli, though the yeast carries the evidence
Food & Timing
With or without food. Do not take with very hot drinks, which kill the yeast.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.