Saccharomyces boulardii
Summary
Saccharomyces boulardii is a probiotic yeast. A meta-analysis of 21 trials with 4,780 people found it cut antibiotic-associated diarrhea from about 19% to 9% (grade A). Rarely, it has caused bloodstream yeast infections, mainly in people with central lines, feeding tubes or intensive care stays, and in very old patients.
Key facts
- A probiotic yeast related to baker’s yeast (Saccharomyces cerevisiae)[3]
- Antibiotic-associated diarrhea fell from 18.7% to 8.5% (RR 0.47); about 10 people need to take it for one to benefit[1]
- Yeast bloodstream infection, mostly with central venous catheters, tube feeding or ICU stays; half of 10 cases in one series died[3]
- A 2010 review of 27 adult trials judged evidence strong for antibiotic-associated and traveler’s diarrhea and promising but insufficient for other uses[2]
- 2 graded human outcomes on this page
- October 11, 2026
How it works
ProposedS. boulardii is a live yeast thought to act inside the gut, for example by competing with harmful microbes; the reviews cited here focus on clinical outcomes rather than mechanism.[2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Antibiotic-associated diarrhea | Improved | Grade A | Meta-analysis · n = 4,780 · 2015 Children and adults taking antibiotics, 21 randomized trials Form: Saccharomyces boulardii · Dose: Varied across trials · Duration: During antibiotic treatment Risk fell from 18.7% to 8.5% (RR 0.47, 95% CI 0.38–0.57; NNT 10); in children from 20.9% to 8.8%, in adults from 17.4% to 8.2%. | 26216624 (opens PubMed)Source [1] |
| Several diarrhea types in adults | Improved | Grade B | Meta-analysis · n = 5,029 · 2010 Adults in 27 placebo-controlled trials Form: Saccharomyces boulardii · Dose: Varied across trials · Duration: Varied across trials S. boulardii was effective in 84% of 31 treatment arms; for antibiotic-associated diarrhea the pooled RR was 0.47. | 20458757 (opens PubMed)Source [2] |
Forms
Studied doses
Doses studied in human trials ranged from 250 mg to 3 g of freeze-dried S. boulardii a day (roughly 5 to 60 billion CFU) for about 1 week to 6 months; adult antibiotic-diarrhea trials mostly used 500 to 1,000 mg a day during the antibiotic course.[2]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Central venous catheter, tube feeding or ICU stay
- Most yeast bloodstream infections linked to the probiotic occurred in these settings.[3]
- Very old age
- In one hospital series, three cases had no other risk factor besides being 80 or older; the authors suggest avoiding it in older patients.[3]
- Weakened immune system
- Discuss any live yeast probiotic with a clinician first.[3]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Saccharomyces boulardii
Products from brands we partner with that contain Saccharomyces boulardii. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkSaccharomyces Boulardii Supplement4 capsules: 20 billion CFU (1,000 mg) Saccharomyces boulardii; 25 servingsShop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
Partner links may earn us a commission. Learn more
Get 15% off with SMART026 (opens in new tab)15% off with code SMART026
Partner links may earn us a commission. Learn more
- Supersmart’s own terms and exclusions apply at checkout.
- 20% applies when 3 or more products ship on auto-delivery to the same address.
- The code discount and Subscribe & Save are separate offers; we don’t claim they combine.
- Offer terms from Supersmart’s site and its affiliate program, checked Oct 8, 2026. Offers can change; the brand's checkout is final.
Frequently asked questions
Does S. boulardii lower the risk of antibiotic diarrhea?
A meta-analysis of 21 trials found it roughly halved the risk, from about 19% to 9%.[1]
When was S. boulardii taken in the trials?
During the antibiotic course, in both children and adults.[1]
Is S. boulardii safe?
For most people in trials, yes; rare bloodstream yeast infections occurred mainly in hospital patients with central lines or feeding tubes.[3]
Is S. boulardii the same as baker’s yeast?
It is closely related to Saccharomyces cerevisiae; bloodstream infections with S. cerevisiae have been linked to S. boulardii probiotics.[3]
Sources
- [1]Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea.. Aliment Pharmacol Ther, 2015. meta-analysis
- [2]Systematic review and meta-analysis of Saccharomyces boulardii in adult patients.. World J Gastroenterol, 2010. meta-analysis
- [3]Saccharomyces cerevisiae fungemia: Risk factors, outcome and links with S. boulardii-containing probiotic administration.. Infect Dis Now, 2021. observational
What changed
- Effect arrows corrected on 2 row(s): outcomes where a harmful measure fell (pain, symptoms, blood pressure, lipids, glucose, risk) now show as improved (up). No study data changed.
- Independent review: studied-dose text now gives the 250 mg–3 g/day range and the 500–1,000 mg/day used in adult antibiotic-diarrhea trials (McFarland 2010, tables 2–6); key-fact grade matched to the evidence table.
- First draft. Every PMID checked against NCBI E-utilities (title, year and journal taken from the PubMed record; retraction and expression-of-concern flags checked: none) and abstracts read for each cited row. Product details in Where to buy read from the brand page on the date shown.