Saccharomyces boulardii

Q: What is Saccharomyces boulardii?

It is a probiotic yeast sold as a supplement. Most research is on one strain, CNCM I-745. It is a yeast, not a bacterium, so antibiotics do not kill it.

Q: Does it prevent diarrhoea from antibiotics?

Probably, yes. A 2015 analysis of 21 trials found diarrhoea fell from 18.7% to 8.5%. A European children's group strongly recommends it for children on antibiotics with risk factors.

Q: Does it help with C. difficile?

The evidence is low certainty. The AGA review found it lowered C. difficile diarrhoea (RR 0.41). In a 2025 trial adding it to vancomycin cut recurrence. It is never a replacement for treatment.

Q: Does it help children with a stomach bug?

Results are mixed. In the best-designed trials probiotics made little or no difference to diarrhoea lasting 48 hours or more.

Q: Does it prevent travellers' diarrhoea?

A 2019 analysis of 6 trials found a modest drop (RR 0.79) for the CNCM I-745 strain. The number of trials is small.

Q: Does it help with H. pylori treatment?

Two 2026 analyses found a small rise in cure rate and fewer side effects when added to standard treatment. It does not treat the infection alone.

Q: Does it help irritable bowel syndrome?

Evidence is mixed. Three trials found no difference in abdominal pain, and a 2026 review called the results conflicting.

Q: Does it help Crohn's disease?

A 165-person trial found no benefit for keeping Crohn disease in remission.

Q: Is it safe?

Mild digestive effects were reported in trials, and some trials found no difference from placebo. Rare serious bloodstream infections have been reported, mostly in very ill hospital patients.

Q: Who should be careful?

People who are seriously ill, in intensive care, have a central line or tube feeding, have a weakened immune system, and preterm infants. Ask a doctor before using it.

Saccharomyces boulardii · also called Probiotic yeast, S. boulardii CNCM I-745

Saccharomyces boulardii is a probiotic yeast sold as a supplement. It is best studied for preventing diarrhoea during antibiotic treatment, with moderate-certainty evidence. Evidence is low for C. difficile, travellers' diarrhoea and as an add-on for H. pylori, mixed for IBS and children's infectious diarrhoea, and against it for keeping Crohn disease in remission. The main caution is a rare, serious bloodstream infection in very ill people.

General information, not medical advice. Last substantive update October 26, 2026 · Not medically reviewed. A named clinician has not signed off on this page. How this page is made

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About Saccharomyces boulardii

Saccharomyces boulardii is a probiotic yeast. Trials support it mainly for preventing diarrhoea during antibiotics. It is not a nutrient, and rare serious infections can happen in very ill people.

What it is

Saccharomyces boulardii is a yeast, not a bacterium, sold as a probiotic. Most of the research is on one strain called CNCM I-745. NCBI Taxonomy lists the name as invalid and places it within Saccharomyces cerevisiae.

Because it is a yeast, antibiotics do not kill it. A 2020 review says it is naturally resistant to antibiotics and cannot spread antibiotic resistance. It is sold as freeze-dried live yeast in capsules or sachets. None of the sources read give a food source or a recommended intake: it is not a nutrient.

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What the research shows

The strongest evidence is for lowering diarrhoea during antibiotics. Pooled trials found a fall from 18.7% to 8.5%. For C. difficile, results are low certainty. Evidence is mixed for children's infectious diarrhoea and IBS, small for H. pylori add-on and travellers' diarrhoea, and against for keeping Crohn disease in remission.

Several reviews of "probiotics" do not separate S. boulardii from other kinds, so they are labelled that way here. Strain matters: a result for one probiotic does not carry over to another.

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How it might work

A 2020 review describes proposed actions, such as sticking to and removing harmful gut microbes and their toxins, and effects on the gut lining and inflammation. These are proposals. The reviewers of the AGA technical review wrote that how it protects against C. difficile is unclear.

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The main safety concern

Rare bloodstream infections with this yeast have been reported, mostly in hospital patients. A 2023 review of 108 cases found 67.6% followed S. boulardii use; intensive care, tube or intravenous feeding, diarrhoea and diabetes were common settings. The overall death rate was 36.1%. These reports cannot show how often it happens.

The US FDA warned in 2023 that live probiotics can cause invasive, potentially fatal infection in preterm infants in hospital. The NHS and NCCIH advise talking to a doctor first if you have a weakened immune system or are seriously ill.

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Strain and label

The NHS says probiotics are classed as food in the UK, so a product may not contain what the label says. NCCIH reports some products with organisms not on the label. Trial results belong to a named strain, most often CNCM I-745, so check the strain name with a pharmacist. This page gives no amounts to take.

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At a glance

Traditional uses history, not proof

Sold as a probiotic supplement; no traditional or food use was found in the sources read

Studied for research

Diarrhoea after antibiotics, moderate certainty
C. difficile infection (prevention and as an add-on), low certainty
Children's infectious diarrhoea, mixed evidence
Travellers' diarrhoea, low certainty
Added to H. pylori treatment, moderate certainty for cure rate
Irritable bowel syndrome, mixed evidence
Crohn's disease, evidence against

Main compounds

Saccharomyces boulardii CNCM I-745 (the most studied strain)

Common forms

Capsules
Powder or sachets (freeze-dried live yeast)

Research links: 2015 meta-analysis: S. boulardii for antibiotic-associated diarrhoea (21 trials) · 2016 ESPGHAN recommendations for children on antibiotics · 2020 AGA technical review of probiotics for gut disorders · 2023 review of Saccharomyces bloodstream infections · 2013 trial: no benefit in Crohn disease (165 people) · Research Library · Genes & Biomarkers Library

What it is and its history

Accepted scientific name: Saccharomyces boulardii (a probiotic yeast; NCBI lists the name as invalid and places it within Saccharomyces cerevisiae)
Naming authority: Not stated
Synonyms: Name: Saccharomyces cerevisiae var. boulardii; Status: used in reviews; not verified against a taxonomy database
Common names: Probiotic yeast (English); S. boulardii CNCM I-745 (English)
Family or group: Yeast (Saccharomycetaceae). Not a bacterium: antibiotics do not kill it.
Classification: Fungi > Ascomycota > Saccharomycetes > Saccharomycetales > Saccharomycetaceae > Saccharomyces > Saccharomyces cerevisiae (boulardii listed as an invalid name)
Cultivation: Not researched.
Harvest and processing: Sold as freeze-dried live yeast in capsules or sachets (per the existing nutrient summary); manufacturing not researched.
Look-alikes and adulterants: Name: Baker's or brewer's yeast (Saccharomyces cerevisiae); Note: NCBI Taxonomy places S. boulardii within S. cerevisiae. Baker's yeast is not the same product and was not shown to give the same results.; Name: Lactobacillus rhamnosus GG and other bacterial probiotics; Note: Bacteria, not yeast. They have separate pages.
Sustainability and conservation: Not assessed.

What is inside, and how it may work

What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.

Main compounds

Compound	Family	Where it is concentrated	Activity studied	Level of evidence
Saccharomyces boulardii CNCM I-745	live probiotic yeast strain	Not read from a source.	The strain most studied in the reviews read (travellers' diarrhoea, IBS, C. difficile). ^{12 10 9}	Human data

Mechanisms, receptors and pathways

Target or pathway	Gene or receptor	What was found	Level
Gut microbes and toxins	Not specified	A 2020 narrative review describes proposed actions: sticking to and removing harmful microbes and toxins, cutting up virulence factors outside the cell, and effects on the gut lining and inflammation. These are proposals, not shown to explain trial results. ⁹	Review of lab and human work
Survival with antibiotics	Not applicable	The same review says the yeast is naturally resistant to antibiotics and cannot spread antibiotic resistance. ⁹	Review
Protection against C. difficile	Not specified	The AGA reviewers wrote that the exact way S. boulardii protects against C. difficile is unclear. ¹⁴	Human trials, mechanism unclear

Absorption, metabolism and elimination

Absorption: Not researched. It is a live yeast that acts in the gut.
Distribution: Not researched.
Elimination: Not researched.

Isolated compounds versus whole extracts

This page is about a live yeast product. Foods that contain other yeasts or ferments were not shown to give the same results, and none of the sources read give a food source or a recommended intake.

Nutritional composition

S. boulardii is not a nutrient and has no food amounts or recommended intake in the sources read. USDA and NIH nutrient data do not apply.

8benefits and uses looked at

22studies and sources checked

Moderate certaintybest evidence rating found

9lab markers tracked in trials

2 moderate certainty2 mixed findings3 low certainty1 evidence against

What was looked at

The 8 benefits and uses checked for Saccharomyces boulardii, each with how strong the evidence is. Tap one to open it.

Diarrhoea after antibiotics (prevention)Moderate certainty
C. difficile diarrhoea in people taking antibiotics (prevention)Low certainty
Added to C. difficile treatmentLow certainty
Short-term infectious diarrhoea in childrenMixed findings
Travellers' diarrhoea (prevention)Low certainty
Added to H. pylori treatmentModerate certainty
Irritable bowel syndrome (IBS)Mixed findings
Crohn's disease (keeping it in remission)Evidence against

Lab markers tracked in the studies

Chance of antibiotic-associated diarrhoeaChance of C. difficile diarrhoeaReturn of C. difficile infectionHow long diarrhoea lasts in childrenChance of travellers' diarrhoeaH. pylori cure rateSide effects of H. pylori treatmentAbdominal pain in IBSRelapse of Crohn's disease

What is Saccharomyces boulardii good for?

The main studied uses and how strong the human evidence is for each. Results belong to the yeast and strain tested, not to other probiotics.

Diarrhoea after antibioticsModerate certaintyA 2015 analysis of 21 trials found diarrhoea during antibiotics fell from 18.7% to 8.5% with S. boulardii. A European children's gut group strongly recommends it, or Lactobacillus rhamnosus GG, for children with risk factors. C. difficile diarrhoea (prevention)Low certaintyThe AGA review found S. boulardii was the only single-strain probiotic with a clear effect (RR 0.41), but certainty is low and the adult-only result was not significant in a 2015 analysis. Added to C. difficile treatmentLow certaintyIn a 2025 trial of 120 adults, adding it to vancomycin gave the same clinical cure but fewer recurrences (1.7% vs 13.1%). Earlier trials were small. It is an add-on, not a replacement. Infectious diarrhoea in childrenMixed findingsIn the best-designed trials, probiotics made little or no difference to diarrhoea lasting 48 hours or more. An AGA pooled look at 10 S. boulardii trials saw about 29 fewer hours, but with very low certainty. Travellers' diarrhoeaLow certaintyA 2019 analysis of 6 trials found S. boulardii CNCM I-745 lowered travellers' diarrhoea (RR 0.79). Added to H. pylori treatmentModerate certaintyTwo 2026 analyses found a small rise in cure rate (adults RR 1.07) and fewer side effects when it was added to standard treatment. Irritable bowel syndromeMixed findingsThree trials (232 adults) found no difference in abdominal pain versus placebo, and a 2026 review called the results conflicting. A small open-label pilot saw improvement, without a placebo. Crohn disease (staying in remission)Evidence againstIn a 2013 trial of 165 adults, relapse was 47.5% with S. boulardii vs 53.2% with placebo, not significantly different.

Benefits, one by one

Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.

Diarrhoea after antibiotics (prevention)

Moderate certainty

In a 2015 pooled analysis of 21 trials (4,780 people), diarrhoea during antibiotic treatment fell from 18.7% with placebo or nothing to 8.5% with S. boulardii. A European children's gut-health group (ESPGHAN, 2016) strongly recommends it, or Lactobacillus rhamnosus GG, for children with risk factors who are given antibiotics.

5 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

The 2015 meta-analysis found a lower risk in children (20.9% to 8.8%) and adults (17.4% to 8.2%). A 2010 review of adult trials found a similar result (RR 0.47). The ESPGHAN group rated the evidence for children as moderate quality. A Cochrane review of all probiotics together in children (33 trials) found 8% vs 19% diarrhoea, moderate certainty, but it does not separate S. boulardii.

Results

S. boulardii probably lowers the chance of diarrhoea while taking antibiotics. It does not work for everyone, and it does not treat the infection the antibiotic is for.

Effect sizes as reported

Risk 18.7% to 8.5% (RR 0.47; NNT 10). Children RR 0.43; adults RR 0.49.

Why this rating

Several pooled analyses agree, and a guideline rates children's evidence moderate. Held below high because trials defined diarrhoea differently and the abstracts give little detail on trial quality.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Children and adults taking antibiotics, in hospital and outpatient groups.

Limits

Diarrhoea was defined by each trial. Results apply to S. boulardii, not to other probiotics. Only abstracts were read for the pooled analyses.

Why researchers looked

Antibiotics can upset the gut and cause diarrhoea. A yeast is not killed by antibiotics, so it is studied alongside them.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Preliminary mechanism

How the yeast might work is described in a 2020 narrative review as proposals: it may stick to and remove harmful gut microbes and their toxins, cut up their virulence factors, and affect the gut lining and inflammation. This has not been shown to explain the trial results.

A proposed mechanism does not show that the effect happens in people.

Rare serious bloodstream infections have been reported; see the Safety tab.

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C. difficile diarrhoea in people taking antibiotics (prevention)

Low certainty

C. difficile is a bowel infection that can follow antibiotics. The American Gastroenterological Association (AGA) technical review found S. boulardii was the only single-strain probiotic that clearly lowered it (RR 0.41), but the certainty is low. In adults alone, a 2015 analysis found no significant drop.

4 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

AGA technical review (2020): S. boulardii RR 0.41 (95% CI 0.22 to 0.79), low certainty. The 2015 meta-analysis: children RR 0.25 (2 trials, 579 children); adults RR 0.8, not significant (9 trials, 1,441). ESPGHAN (2016) suggested S. boulardii for children, conditional, low quality. A 2025 Cochrane review of all probiotics found C. difficile diarrhoea fell from 3.2% to 1.6% (RR 0.50), low certainty, but does not separate S. boulardii.

Results

Some evidence of lower risk, mainly in children. In adults the result was not clear. The certainty is low.

Effect sizes as reported

AGA: RR 0.41. Children RR 0.25; adults RR 0.8 (not significant).

Why this rating

Low certainty in the AGA review; adult-only results were not significant and the trials are few.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Children and adults on antibiotics. In people at low risk the absolute drop is small.

Limits

The Cochrane review notes probiotic-company links in 28 of 47 studies. Not a replacement for infection control or for treatment.

Why researchers looked

C. difficile infection can be serious and often returns, so people look for ways to prevent it.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Antibiotics do not typically kill yeast. The AGA reviewers wrote that how S. boulardii protects is unclear.

A proposed mechanism does not show that the effect happens in people.

People with weak immune systems or central lines should ask a doctor first; see Safety.

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Added to C. difficile treatment

Low certainty

In one 2025 trial of 120 adults, S. boulardii added to vancomycin gave the same clinical cure but fewer recurrences (1.7% vs 13.1%). The AGA review of earlier small trials found low-certainty signs that it may help diarrhoea stop and lower recurrence. It is studied only as an add-on, never as a replacement.

2 studiesCapsules given together with vancomycin in the 2025 trial; the AGA tr…

Studies, doses and limits

What the trials found

AGA technical review: 5 small trials with 223 adults; the largest (124 adults) gave 1 g a day and found more stopping of diarrhoea (RR 1.33) and less recurrence (RR 0.59), low certainty. The 2025 trial found clinical cure 98.4% vs 98.3%, global cure 96.6% vs 85.3%, recurrence 1.7% vs 13.1%. The AGA review rated overall certainty low.

Results

Possible fewer recurrences when added to standard antibiotics, from small trials. Standard treatment is still needed.

Effect sizes as reported

Recurrence 1.7% vs 13.1% in the 2025 trial; AGA RR 0.59 for recurrence.

Why this rating

Few, small trials; one 2025 trial of 120 people with few recurrences. AGA certainty low.

Form and dose studied

Capsules given together with vancomycin in the 2025 trial; the AGA trials used various amounts. Not advice.

Who was studied

Adults with C. difficile infection.

Limits

Small trials, mixed patient groups, high dropout in some. Serious illness raises the fungemia risk.

Why researchers looked

C. difficile infection often comes back after treatment, so add-ons are tested.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established. The proposed gut actions in reviews have not been shown to explain these results.

A proposed mechanism does not show that the effect happens in people.

The AGA review noted more constipation with S. boulardii in one trial. See Safety for fungemia.

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Short-term infectious diarrhoea in children

Mixed findings

Results are mixed. A Cochrane review of 82 trials (mostly children) found that in the best-designed trials probiotics probably made little or no difference to diarrhoea lasting 48 hours or longer. The AGA technical review pooled 10 S. boulardii trials and saw about 29 fewer hours of diarrhoea, but with very low certainty.

2 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

Cochrane 2020: 82 trials, 12,127 people; low-risk-of-bias trials showed no difference for diarrhoea lasting 48 h or more (RR 1.00); results were similar in the S. boulardii subgroup; high heterogeneity and publication bias. AGA 2020: S. boulardii studied in 22 trials in children with gastroenteritis; for the 10 reporting duration, 28.77 hours fewer (very low certainty).

Results

The shorter-diarrhoea results come from lower-quality trials; the best-designed trials show little or no difference.

Effect sizes as reported

Cochrane: RR 1.00 for diarrhoea lasting 48 h or more. AGA: 28.77 hours fewer, very low certainty.

Why this rating

The two reviews disagree by trial quality; many trials were at high or unclear risk of bias and publication bias was seen.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Mostly children with acute infectious diarrhoea, in many countries.

Limits

Study definitions of diarrhoea varied. The AGA review notes no North American trials in this analysis.

Why researchers looked

Gastroenteritis is very common in children, so shortening it is a popular goal.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

A very young or seriously ill child with diarrhoea needs a doctor, not a supplement.

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Travellers' diarrhoea (prevention)

Low certainty

A 2019 pooled analysis of 6 trials found S. boulardii CNCM I-745 lowered travellers' diarrhoea (RR 0.79). Lactobacillus rhamnosus GG showed only a trend and L. acidophilus showed no significant effect.

2 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

McFarland and Goh 2019: 12 trials in the review, 6 trials (9 arms) in the meta-analysis. S. boulardii CNCM I-745 RR 0.79 (0.72 to 0.87). A 2010 review of adult trials also supported prevention of travellers' diarrhoea (its author's view).

Results

May lower the chance of travellers' diarrhoea. There are few trials.

Effect sizes as reported

RR 0.79

Why this rating

A modest drop from few trials; only abstracts were read.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Travellers going abroad.

Limits

Few trials per strain; industry details not in the abstract.

Why researchers looked

Travellers' diarrhoea affects millions of tourists each year.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

See the Safety tab for rare serious infections.

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Added to H. pylori treatment

Moderate certainty

H. pylori is a stomach infection treated with several medicines. Two 2026 pooled analyses found that adding S. boulardii raised the cure rate a little and lowered side effects such as diarrhoea and nausea. It is studied only as an add-on, not on its own.

2 studiesAdded to standard antibiotic treatment; amounts varied by trial. Not …

Studies, doses and limits

What the trials found

Chang 2026: 19 trials; adults RR 1.07 (1.03 to 1.10), about 5.7 percentage points, NNT 18; children RR 1.12 (1.03 to 1.23); side effects 19.7% vs 36.0% (RR 0.51, 0.39 to 0.66). The authors rate certainty moderate for eradication and low for side effects. Westphal 2026 also found higher eradication and fewer cases of diarrhoea, nausea and epigastric pain; more studies are needed for bismuth quadruple therapy.

Results

A small gain in cure rate and fewer side effects when added to standard H. pylori treatment.

Effect sizes as reported

Adults RR 1.07; side effects RR 0.51

Why this rating

Two 2026 pooled analyses agree, and the first rates eradication moderate by GRADE. The gain is small and only abstracts were read.

Form and dose studied

Added to standard antibiotic treatment; amounts varied by trial. Not advice.

Who was studied

Adults and children being treated for H. pylori.

Limits

Small absolute gain; benefit with bismuth quadruple therapy unclear.

Why researchers looked

Treatment for H. pylori has many side effects, so add-ons are tested.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

Do not stop prescribed medicines. Ask the prescriber.

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Irritable bowel syndrome (IBS)

Mixed findings

Evidence is mixed. Three trials with 232 adults found no difference in abdominal pain compared with placebo (AGA review). A 2026 review called the results for S. boulardii CNCM I-745 conflicting. A small 2023 open-label pilot in IBS with diarrhoea saw symptom improvement, but had no placebo.

3 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

AGA 2020: 3 trials, 232 adults, abdominal pain SMD 0.26 (-0.09 to 0.61), very low certainty. Maslennikov 2026: conflicting results for S. boulardii CNCM I-745, while some other strains helped. Bustos Fernandez 2023: 48 analysed; symptom score -134 vs -93; diarrhoea 25.9% vs 47.6%; open label, 15 days.

Results

No reliable benefit shown for IBS.

Effect sizes as reported

Pain SMD 0.26 (not significant)

Why this rating

Pooled trials show no clear benefit; the one positive pilot was small and open label.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Adults with IBS, including diarrhoea-predominant IBS with bacterial overgrowth.

Limits

Different outcome measures; small trials.

Why researchers looked

IBS is common and people try many supplements for it.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

Ongoing or severe bowel symptoms need a doctor.

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Crohn's disease (keeping it in remission)

Evidence against

In a 2013 trial of 165 adults in remission, relapse after 52 weeks was 47.5% with S. boulardii vs 53.2% with placebo, a difference that was not significant. The AGA review also found no clear benefit.

2 studiesFreeze-dried live yeast (capsule or sachet), most often the strain ca…

Studies, doses and limits

What the trials found

Bourreille 2013: S. boulardii 1 g a day for 52 weeks vs placebo, relapse 47.5% vs 53.2%, no difference in time to relapse, activity score, ESR or CRP. AGA 2020: 2 trials, 191 people, RR 0.51 (0.10 to 2.54), very low certainty.

Results

No benefit shown for staying in remission.

Effect sizes as reported

Relapse 47.5% vs 53.2% (not significant)

Why this rating

A good-sized randomised trial found no benefit; pooled evidence is very low certainty.

Form and dose studied

Freeze-dried live yeast (capsule or sachet), most often the strain called CNCM I-745. Results belong to the strain tested. This is not advice on what to take.

Who was studied

Adults with Crohn disease in remission after steroids or aminosalicylates.

Limits

A post hoc non-smoker result is not reliable by itself.

Why researchers looked

Crohn's disease often relapses, so people look for ways to stay well.

Traditional use

Saccharomyces boulardii is a probiotic yeast sold as a supplement. None of the sources read describe a traditional or food use.

Proposed mechanism Not established

Not established.

A proposed mechanism does not show that the effect happens in people.

Do not stop prescribed Crohn medicines.

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Connections to the rest of health

How Saccharomyces boulardii connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.

Explore every connection: goals, body systems, organs, symptoms, genes

Kind of connection Connected to Search

A. Wellness goals

Connected to	Evidence status	Context	Studies
Digestive Support	Moderate certainty	Diarrhoea after antibiotics (prevention): In a 2015 pooled analysis of 21 trials (4,780 people), diarrhoea during antibiotic treatment fell from 18.7% with placebo or nothing to 8.5% with S. boulardii. A European children's gut-health group (ESPGHAN, 2016) strongly recommends it, or Lactobacillus rhamnosus GG, for children with risk factors who are given antibiotics. Added to H. pylori treatment: H. pylori is a stomach infection treated with several medicines. Two 2026 pooled analyses found that adding S. boulardii raised the cure rate a little and lowered side effects such as diarrhoea and nausea. It is studied only as an add-on, not on its own.	^{15 16 11 8 9 4 18}
Gut Health	Moderate certainty	Diarrhoea after antibiotics (prevention): In a 2015 pooled analysis of 21 trials (4,780 people), diarrhoea during antibiotic treatment fell from 18.7% with placebo or nothing to 8.5% with S. boulardii. A European children's gut-health group (ESPGHAN, 2016) strongly recommends it, or Lactobacillus rhamnosus GG, for children with risk factors who are given antibiotics.	^{15 16 11 8 9}
Digestive Support	Low certainty	C. difficile diarrhoea in people taking antibiotics (prevention): C. difficile is a bowel infection that can follow antibiotics. The American Gastroenterological Association (AGA) technical review found S. boulardii was the only single-strain probiotic that clearly lowered it (RR 0.41), but the certainty is low. In adults alone, a 2015 analysis found no significant drop. Added to C. difficile treatment: In one 2025 trial of 120 adults, S. boulardii added to vancomycin gave the same clinical cure but fewer recurrences (1.7% vs 13.1%). The AGA review of earlier small trials found low-certainty signs that it may help diarrhoea stop and lower recurrence. It is studied only as an add-on, never as a replacement.	^{14 15 16 7 5 12 11}
Gut Health	Low certainty	C. difficile diarrhoea in people taking antibiotics (prevention): C. difficile is a bowel infection that can follow antibiotics. The American Gastroenterological Association (AGA) technical review found S. boulardii was the only single-strain probiotic that clearly lowered it (RR 0.41), but the certainty is low. In adults alone, a 2015 analysis found no significant drop. Travellers' diarrhoea (prevention): A 2019 pooled analysis of 6 trials found S. boulardii CNCM I-745 lowered travellers' diarrhoea (RR 0.79). Lactobacillus rhamnosus GG showed only a trend and L. acidophilus showed no significant effect.	^{14 15 16 7 12 11}
Digestive Support	Mixed findings	Short-term infectious diarrhoea in children: Results are mixed. A Cochrane review of 82 trials (mostly children) found that in the best-designed trials probiotics probably made little or no difference to diarrhoea lasting 48 hours or longer. The AGA technical review pooled 10 S. boulardii trials and saw about 29 fewer hours of diarrhoea, but with very low certainty. Irritable bowel syndrome (IBS): Evidence is mixed. Three trials with 232 adults found no difference in abdominal pain compared with placebo (AGA review). A 2026 review called the results for S. boulardii CNCM I-745 conflicting. A small 2023 open-label pilot in IBS with diarrhoea saw symptom improvement, but had no placebo.	^{6 14 10 3}
Gut Health	Mixed findings	Short-term infectious diarrhoea in children: Results are mixed. A Cochrane review of 82 trials (mostly children) found that in the best-designed trials probiotics probably made little or no difference to diarrhoea lasting 48 hours or longer. The AGA technical review pooled 10 S. boulardii trials and saw about 29 fewer hours of diarrhoea, but with very low certainty. Irritable bowel syndrome (IBS): Evidence is mixed. Three trials with 232 adults found no difference in abdominal pain compared with placebo (AGA review). A 2026 review called the results for S. boulardii CNCM I-745 conflicting. A small 2023 open-label pilot in IBS with diarrhoea saw symptom improvement, but had no placebo.	^{6 14 10 3}
Digestive Support	Evidence against	Crohn's disease (keeping it in remission): In a 2013 trial of 165 adults in remission, relapse after 52 weeks was 47.5% with S. boulardii vs 53.2% with placebo, a difference that was not significant. The AGA review also found no clear benefit.	^{2 14}

B. Body systems

Connected to	Kind of connection	Evidence status	Context	Studies
Digestive System	Biological association	Moderate certainty	Studied for: Diarrhoea after antibiotics (prevention) Studied for: C. difficile diarrhoea in people taking antibiotics (prevention)	^{15 16 11 8 9 14 7 5 6 12 4 18 10 3 2}

E. Health conditions

Connected to	Kind of connection	Evidence status	Context	Studies
Yeast bloodstream infection (fungemia)	Adverse effect or risk	Documented risk	Rare serious bloodstream infections reported, mainly in critically ill people. Preparation or compound: Saccharomyces boulardii probiotics	^{17 13 1}
C. difficile infection		Preliminary	Low-certainty evidence for lower risk and fewer recurrences. Preparation or compound: Saccharomyces boulardii	^{14 5}
Antibiotic-associated diarrhoea		Clinical trial evidence	Lower risk of diarrhoea in pooled trials. Preparation or compound: Saccharomyces boulardii	^{15 16}

I. Biomarkers

Connected to	Kind of connection	Evidence status	Context	Studies
Chance of antibiotic-associated diarrhoea	Biological association	Moderate certainty	Measured in trials: lower. A lab change is not the same as a health benefit.	¹⁵
Chance of C. difficile diarrhoea	Biological association	Low certainty	Measured in trials: lower. A lab change is not the same as a health benefit.	^{14 15}
Return of C. difficile infection	Biological association	Low certainty	Measured in trials: lower (small trials). A lab change is not the same as a health benefit.	^{5 14}
How long diarrhoea lasts in children	Biological association	Mixed findings	Measured in trials: shorter in lower-quality trials; no clear change in the best trials. A lab change is not the same as a health benefit.	^{14 6}
Chance of travellers' diarrhoea	Biological association	Low certainty	Measured in trials: lower. A lab change is not the same as a health benefit.	¹²
H. pylori cure rate	Biological association	Moderate certainty	Measured in trials: higher. A lab change is not the same as a health benefit.	^{4 18}
Side effects of H. pylori treatment	Biological association	Low certainty	Measured in trials: lower. A lab change is not the same as a health benefit.	^{4 18}
Abdominal pain in IBS	Biological association	Very low certainty	Measured in trials: no clear change. A lab change is not the same as a health benefit.	¹⁴
Relapse of Crohn's disease	Biological association	Low certainty	Measured in trials: no difference. A lab change is not the same as a health benefit.	²

K. Biological pathways

Connected to	Kind of connection	Evidence status	Context	Studies
Clostridioides difficile	Preliminary mechanism	Human	S. boulardii was studied for preventing and treating this infection (low certainty).	^{14 5}
Helicobacter pylori	Preliminary mechanism	Human	Added to eradication treatment in trials.	⁴

L. Active compounds

Connected to	Kind of connection	Evidence status	Context	Studies
Saccharomyces boulardii CNCM I-745	Biological association	Human	The strain most studied in the reviews read (travellers' diarrhoea, IBS, C. difficile).	^{12 10 9}

Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).

Evidence at a glance: what the research found for 8 outcomes

2Moderate certainty

3Low certainty

2Mixed findings

1Evidence against

Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.

Diarrhoea after antibiotics (prevention) 5 studies Moderate certainty C. difficile diarrhoea in people taking antibiotics (prevention) 4 studies Low certainty Added to C. difficile treatment 2 studies Low certainty Short-term infectious diarrhoea in children 2 studies Mixed findings Travellers' diarrhoea (prevention) 2 studies Low certainty Added to H. pylori treatment 2 studies Moderate certainty Irritable bowel syndrome (IBS) 3 studies Mixed findings Crohn's disease (keeping it in remission) 2 studies Evidence against

The evidence

The research centre for Saccharomyces boulardii. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.

Evidence by outcome

Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).

How we rate evidence

High certainty

Several well-run trials or reviews agree; further research is unlikely to change the picture much.

Moderate certainty

Good trials point the same way, but some doubt remains.

Low certainty

Small, short or inconsistent trials. The finding could change with better research.

Very low certainty

Very little or very weak human data. Treat as a possibility only.

Mixed findings

Trials or reviews disagree with each other.

Not enough evidence

Not enough human research to say either way.

Evidence against

Good research found no benefit, or found harm.

We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our existing summary of the yeast, then re-read PubMed abstracts for reviews, guidelines, trials and case reports, the open full text of the AGA technical review, and the NCCIH, NHS and FDA pages. Only abstracts were read for most studies. The NIH Office of Dietary Supplements page was blocked and is marked unread.

Study library: every study we checked 22

Design Research type Year from Search

Study	Design	People	Product, dose, length	Result
Atici 2017 Catheter-related Saccharomyces cerevisiae Fungemia Following Saccharomyces boulardii Probiotic Treatment: In a child in intensive care unit and review of the literature. Med Mycol Case Rep · PMID 28280685 · DOI	Case report	1 An 8-year-old in paediatric surgical intensive care	S. boulardii probiotic, then fungemia	The child developed S. cerevisiae bloodstream infection after S. boulardii probiotic treatment. Caspofungin was not effective; amphotericin B was used. The authors advise caution with probiotics in critically ill patients. One case. (Not applicable) Methods, limits and funding Outcomes: Course and treatment of the infection Limitations: A single case report cannot show how often this happens. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Bourreille 2013 Saccharomyces boulardii does not prevent relapse of Crohn's disease. Clin Gastroenterol Hepatol · PMID 23466709 · DOI	Randomised controlled trial	165 165 adults with Crohn's disease in remission after steroids or aminosalicylates	Saccharomyces boulardii Capsule or sachet of freeze-dried yeast 1 g a day (studied in the trial) 52 weeks · vs Placebo	Relapse happened in 47.5% of the S. boulardii group and 53.2% of the placebo group, a non-significant difference. Time to relapse, disease activity scores and inflammation markers (ESR, CRP) did not differ. A post hoc look at non-smokers suggested less relapse, but needs confirmation. The authors judged it safe and well tolerated. Relapse 47.5% vs 53.2% (not significant). (Not in the abstract) Methods, limits and funding Outcomes: Share still in remission at week 52; time to relapse; disease activity score; inflammation markers Limitations: A post hoc subgroup finding in non-smokers is not reliable on its own. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Bustos Fernandez 2023 Impact of Saccharomyces boulardii CNCM I-745 on Bacterial Overgrowth and Composition of Intestinal Microbiota in Diarrhea-Predominant Irritable Bowel Syndrome Patients: Results of a Randomized Pilot Study. Dig Dis · PMID 36630947 · DOI	Randomised controlled trial	54 54 adults with diarrhoea-predominant IBS and bacterial overgrowth of the small intestine (48 analysed)	Saccharomyces boulardii CNCM I-745 plus dietary advice Capsule or sachet of freeze-dried yeast 15 days · vs Dietary advice only (open label, no placebo)	Hydrogen on the breath test fell 41% vs 29%. The IBS symptom score fell by 134 vs 93 points. The share with diarrhoea was 25.9% vs 47.6%. The authors call safety excellent. Because it was open label with no placebo, expectation could explain part of the result. Symptom score -134 vs -93; diarrhoea 25.9% vs 47.6%. (Not in the abstract) Methods, limits and funding Outcomes: Breath-test hydrogen; IBS symptom score; share with diarrhoea; gut microbiota Limitations: Small, open-label pilot with no placebo and only 15 days. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Chang 2026 Saccharomyces boulardii as an Adjunct to Helicobacter pylori Eradication Therapy: A Systematic Review and Meta-Analysis. J Dig Dis · PMID 42764401 · DOI	Systematic review meta analysis	19 randomised trials in adults (15 trials) and children (3 trials) having H. pylori eradication treatment	Saccharomyces boulardii added to standard H. pylori antibiotic treatment Capsule or sachet of freeze-dried yeast The authors say 5 x 10^9 to 1 x 10^10 CFU a day for 10 to 14 days appeared reasonable (their view, not advice) 10 to 14 days in many trials · vs Placebo plus the same eradication treatment	Adding S. boulardii raised eradication in adults (RR 1.07, about 5.7 percentage points, NNT 18) and in children (RR 1.12, about 9.8 points, NNT 10), mainly with triple therapy. Overall side effects were about halved (19.7% vs 36.0%). The authors rate certainty moderate for eradication and low for side effects. Adults RR 1.07 (ARD +5.7%, NNT 18); children RR 1.12 (ARD +9.8%, NNT 10); adverse events RR 0.51. (Adults 1.03 to 1.10; children 1.03 to 1.23; adverse events 0.39 to 0.66) Methods, limits and funding Outcomes: H. pylori eradication; adverse events Limitations: 12 of the 19 trials used triple therapy; the benefit with bismuth quadruple therapy is less clear. Read from the abstract only. S. boulardii does not treat H. pylori by itself. Funding and conflicts: Funding and conflicts not stated in the abstract. Registration: PROSPERO CRD420251271815 Read: abstract
Chitapanarux 2025 Efficacy and safety of Saccharomyces boulardii as adjunct therapy with Vancomycin in treating Clostridioides difficile infection: A randomized controlled trial. Sci Rep · PMID 40457042 · DOI	Randomised controlled trial	120 120 adults with mild to moderate C. difficile infection (positive stool toxin test)	Saccharomyces boulardii capsules plus vancomycin Capsule or sachet of freeze-dried yeast Two 250 mg capsules every 12 hours (studied in the trial) 10 days · vs Placebo plus vancomycin	Clinical cure was the same in both groups (98.4% vs 98.3%). The S. boulardii group had a higher global cure rate (96.6% vs 85.3%) and fewer recurrences (1.7% vs 13.1%). No differences were found in diarrhoea outcomes, functional ability or adverse events. Global cure 96.6% vs 85.3% (p=0.044); recurrence 1.7% vs 13.1% (p=0.032). (p=0.044 (global cure); p=0.032 (recurrence); confidence intervals not in the abstract) Methods, limits and funding Outcomes: Clinical cure; recurrence; global cure; diarrhoea outcomes; adverse events Limitations: A single trial of 120 people with few recurrences, so the result is fragile. Read from the abstract only. Short follow-up is not detailed in the abstract. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Collinson 2020 Probiotics for treating acute infectious diarrhoea. Cochrane Database Syst Rev · PMID 33295643 · DOI	Systematic review meta analysis	12127 82 trials: 11,526 children and 412 adults with acute infectious diarrhoea	Many probiotics; subgroups for Lactobacillus rhamnosus GG and Saccharomyces boulardii were looked at Capsule or sachet of freeze-dried yeast Varies Varies · vs Placebo or no probiotic	In the trials at low risk of bias, probiotics probably made little or no difference to diarrhoea lasting 48 hours or longer (RR 1.00), and the effect on how long diarrhoea lasts was very low certainty. Results did not differ when only L. rhamnosus GG or S. boulardii trials were looked at. No serious adverse events were attributed to probiotics. Lasting 48 h or more RR 1.00 (2 trials, 1,770). Duration 8.64 hours shorter, not significant (6 trials, 3,058). (RR 1.00 (0.91 to 1.09); duration MD 8.64 hours shorter (29.4 shorter to 12.1 longer)) Methods, limits and funding Outcomes: Diarrhoea lasting 48 hours or more; duration of diarrhoea; hospital stay; adverse events Limitations: Many trials had high or unclear risk of bias, results varied a lot, and publication bias was seen. The S. boulardii numbers are not given separately in the abstract. Funding and conflicts: Funding not stated in the abstract. Read: abstract
Esmaeilinezhad 2025 Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children. Cochrane Database Syst Rev · PMID 40931979 · DOI	Systematic review meta analysis	15260 47 randomised trials in adults and children receiving antibiotics (38 trials, 13,179 people, for the main result)	Many probiotics, any strain; results are not split by strain in the abstract Capsule or sachet of freeze-dried yeast Varies Varies · vs Placebo, alternative prophylaxis or no treatment	Probiotics may lower CDAD from 3.2% to 1.6% (low certainty). Adverse events were probably not higher with probiotics. The review says short-term use was likely not linked to harm in people who are not immunocompromised. CDAD RR 0.50; absolute drop 1.6%; NNT 65. Adverse events RR 0.86 (moderate certainty). (CDAD RR 0.50 (0.38 to 0.64); adverse events RR 0.86 (0.72 to 1.01); NNT 65 (48 to 97)) Methods, limits and funding Outcomes: Incidence of C. difficile-associated diarrhoea (CDAD); adverse events; length of stay Limitations: All probiotics pooled; S. boulardii is not separated in the abstract. Low certainty for CDAD because of few events and publication bias. About 30% of studies had no registered protocol. Funding and conflicts: Probiotic-company affiliation or financial support in 28 of the 47 studies; the review itself had no funding. Read: abstract
Guo 2019 Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev · PMID 31039287 · DOI	Systematic review meta analysis	6352 33 trials in children aged 0 to 18 given antibiotics	Many probiotics (Lactobacilli, Bifidobacteria, Saccharomyces and others, alone or mixed); results are not split by strain in the abstract Capsule or sachet of freeze-dried yeast High dose (5 billion CFU a day or more) vs low dose compared; amounts vary 5 days to 12 weeks follow-up · vs Placebo, active control or no treatment	Probiotics lowered diarrhoea from 19% to 8% (moderate certainty). The benefit was clearer at 5 billion CFU a day or more. No serious adverse events were attributed to probiotics. Incidence 8% vs 19%; RR 0.45; NNTB 9. High-dose subgroup RR 0.37. (RR 0.45 (0.36 to 0.56); high-dose RR 0.37 (0.30 to 0.46); NNTB 9 (7 to 13)) Methods, limits and funding Outcomes: Incidence of antibiotic-associated diarrhoea; adverse events Limitations: Covers many probiotic types together, so it does not show S. boulardii on its own. Risk of bias was high in 20 of 33 trials. The abstract names S. boulardii only as an example of a high-dose product. Funding and conflicts: Funding not stated in the abstract. Read: abstract
Kazmierczak-Siedlecka 2020 Saccharomyces boulardii CNCM I-745: A Non-bacterial Microorganism Used as Probiotic Agent in Supporting Treatment of Selected Diseases. Curr Microbiol · PMID 32472262 · DOI	Narrative review review of lab and human work	Narrative review of S. boulardii CNCM I-745 and gut-related conditions	Saccharomyces boulardii CNCM I-745	Describes proposed ways the yeast works: sticking to and removing harmful gut microbes and their toxins, cutting up virulence factors outside the cell, and effects on the gut lining and inflammation. Notes the yeast is naturally resistant to antibiotics and cannot spread antibiotic resistance. Notes that fungemia cases have occurred. No numbers. (Not applicable) Methods, limits and funding Outcomes: Mechanisms and clinical uses Limitations: A narrative (not systematic) review, so its mechanism statements are proposals, not proof. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Maslennikov 2026 Strain-Specific Systematic Review with Meta-Analysis of Probiotics Efficacy in the Treatment of Irritable Bowel Syndrome. J Clin Med · PMID 41682832 · DOI	Systematic review meta analysis	32 articles on 10 single-strain probiotics in people with irritable bowel syndrome	Ten single-strain probiotics, including S. boulardii CNCM I-745 Capsule or sachet of freeze-dried yeast Varies Varies · vs Placebo	Several other strains improved IBS symptoms in meta-analyses, but results for Saccharomyces boulardii CNCM I-745 were conflicting. S. boulardii CNCM I-745: conflicting results. (Not in the abstract) Methods, limits and funding Outcomes: Key IBS symptoms; quality of life Limitations: Read from the abstract only. The abstract does not give S. boulardii trial numbers. Funding and conflicts: Funding not stated in the abstract. Registration: PROSPERO CRD420251047092 Read: abstract
McFarland 2010 Systematic review and meta-analysis of Saccharomyces boulardii in adult patients. World J Gastroenterol · PMID 20458757 · DOI	Systematic review meta analysis	5029 27 randomised placebo-controlled trials (31 treatment arms) in adults, 1976 to 2009	Saccharomyces boulardii Capsule or sachet of freeze-dried yeast Varies · vs Placebo	S. boulardii was judged significantly effective and safe in 84% of the treatment arms. For preventing antibiotic-associated diarrhoea the pooled risk ratio was 0.47. The author said it showed promise for C. difficile recurrence, IBS, acute adult diarrhoea, Crohn disease, giardiasis and HIV-related diarrhoea, but more evidence was needed for those. AAD prevention RR 0.47. (RR 0.47 (0.35 to 0.63)) Methods, limits and funding Outcomes: Antibiotic-associated diarrhoea and other adult gut conditions; safety Limitations: An older review (to 2009). Industry ties are not stated in the abstract. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
McFarland 2019 Are probiotics and prebiotics effective in the prevention of travellers' diarrhea: A systematic review and meta-analysis. Travel Med Infect Dis · PMID 30278238 · DOI	Systematic review meta analysis	12 trials in the review; 6 trials (9 treatment arms) in the meta-analysis, in travellers	Saccharomyces boulardii CNCM I-745; also L. rhamnosus GG and L. acidophilus compared Capsule or sachet of freeze-dried yeast · vs Placebo	S. boulardii CNCM I-745 significantly lowered travellers' diarrhoea (RR 0.79). L. rhamnosus GG showed only a trend and L. acidophilus showed no significant effect. RR 0.79 for S. boulardii CNCM I-745. (RR 0.79 (0.72 to 0.87), p < 0.001) Methods, limits and funding Outcomes: Incidence of travellers' diarrhoea Limitations: Only a few trials per strain. Read from the abstract only. Industry links are not stated in the abstract. Funding and conflicts: Funding not stated in the abstract. Read: abstract
Poncelet 2021 Saccharomyces cerevisiae fungemia: Risk factors, outcome and links with S. boulardii-containing probiotic administration. Infect Dis Now · PMID 33934809 · DOI	Case series	10 10 patients with S. cerevisiae bloodstream infection at one hospital group (2005 to 2017)	S. boulardii-containing probiotic given to 6 of 10 patients	80% had tube or intravenous feeding and 70% a central venous line; 30% were in intensive care. Six had been given an S. boulardii probiotic. Three patients without ICU or catheter risk were 80 or older. Half died. The authors suggest older age should be a contraindication for these probiotics (their opinion). 6 of 10 had been given S. boulardii; mortality 50%. (Not applicable) Methods, limits and funding Outcomes: Risk factors; outcome Limitations: A small retrospective series; cannot show cause. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Preidis 2020 AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology · PMID 32531292 · DOI	Systematic review meta analysis	Systematic review behind the American Gastroenterological Association guideline; trials in adults and children with gut disorders	Saccharomyces boulardii and other probiotics, reported strain by strain Capsule or sachet of freeze-dried yeast 1 g a day (3 x 10^10 CFU a day) in the largest C. difficile treatment trial Varies · vs Placebo, no treatment or other	C. difficile diarrhoea prevention: S. boulardii was the only single-strain probiotic with a significant effect (RR 0.41, low certainty). C. difficile treatment add-on: in the largest of 5 small trials (124 adults) it may raise the stopping of diarrhoea (RR 1.33) and lower recurrence (RR 0.59), low certainty. Crohn disease: no clear benefit (2 trials, 191 people, very low). IBS: no difference in abdominal pain (3 trials, 232 adults, very low). Children with gastroenteritis: 10 S. boulardii trials suggested 28.77 fewer hours of diarrhoea, very low certainty. Side effects were mild; one trial reported more constipation with S. boulardii. CDAD prevention RR 0.41; treatment add-on cessation RR 1.33, recurrence RR 0.59; Crohn relapse RR 0.51; IBS pain SMD 0.26; children 28.77 hours fewer. (CDAD prevention RR 0.41 (0.22 to 0.79); cessation RR 1.33 (1.02 to 1.74); recurrence RR 0.59 (0.35 to 0.98); Crohn RR 0.51 (0.10 to 2.54); IBS pain SMD 0.26 (-0.09 to 0.61); children -28.77 h (-40.35 to -17.18)) Methods, limits and funding Outcomes: C. difficile infection (prevention and treatment); Crohn disease; irritable bowel syndrome; acute gastroenteritis in children; adverse events Limitations: Most results are low or very low certainty. The authors note small trials, high dropout, mixed patient groups and no North American trials in the children analysis. The abstract has no text on PubMed, so the open full text on PubMed Central was read instead. Funding and conflicts: Funding: US National Institutes of Health grants to two authors. Several authors report advisory-board, speaker or consulting roles with drug and biotech companies; none is stated as a maker of S. boulardii products in the parts read. Read: full-text
Szajewska 2015 Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Aliment Pharmacol Ther · PMID 26216624 · DOI	Systematic review meta analysis	4780 21 randomised trials in children and adults taking antibiotics	Saccharomyces boulardii Capsule or sachet of freeze-dried yeast · vs Placebo or no treatment	S. boulardii lowered the risk of antibiotic-associated diarrhoea from 18.7% to 8.5% (NNT 10). In children 20.9% to 8.8%; in adults 17.4% to 8.2%. It lowered C. difficile diarrhoea in children (2 trials, 579 children) but the drop in adults (9 trials, 1,441) was not significant. AAD: RR 0.47 (NNT 10). Children RR 0.43; adults RR 0.49. CDAD: children RR 0.25; adults RR 0.8 (not significant). (AAD RR 0.47 (95% CI 0.38 to 0.57); children 0.43 (0.3 to 0.6); adults 0.49 (0.38 to 0.63); NNT 10 (9 to 13); CDAD children 0.25 (0.08 to 0.73); adults 0.8 (0.47 to 1.34)) Methods, limits and funding Outcomes: Antibiotic-associated diarrhoea (AAD); C. difficile-associated diarrhoea (CDAD) Limitations: Definitions of diarrhoea varied between trials as set by each investigator. Read from the abstract only. Individual trial quality is not detailed in the abstract. Funding and conflicts: Authors: no funding or conflict statement in the abstract; PubMed lists non-US government research support. Read: abstract
Szajewska 2016 Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Children. J Pediatr Gastroenterol Nutr · PMID 26756877 · DOI	Consensus guideline	Children receiving antibiotics (recommendations from the ESPGHAN probiotics working group)	Saccharomyces boulardii (and Lactobacillus rhamnosus GG) Capsule or sachet of freeze-dried yeast	If probiotics are considered for children with risk factors for antibiotic-associated diarrhoea, the group recommended Lactobacillus rhamnosus GG or Saccharomyces boulardii (moderate quality of evidence, strong recommendation). For preventing C. difficile diarrhoea the group suggested S. boulardii (low quality of evidence, conditional recommendation). No effect sizes in the abstract. (Not applicable) Methods, limits and funding Outcomes: Prevention of antibiotic-associated diarrhoea and of C. difficile-associated diarrhoea in children Limitations: A professional-society recommendation, not a trial. It covers prevention in children only, not treatment. Read from the abstract only. Funding and conflicts: Authors are members of the ESPGHAN working group; funding not stated in the abstract. Read: abstract
Vinayagamoorthy 2023 Epidemiology of Saccharomyces fungemia: A systematic review. Med Mycol · PMID 36806741 · DOI	Systematic review	108 108 reported cases of Saccharomyces bloodstream infection (2005 to 2022)	Saccharomyces fungemia, with and without S. boulardii probiotic use · vs Cases without probiotic compared	Of 108 cases, 73 (67.6%) were in people given S. boulardii probiotics. Common settings were intensive care stay (31.5%), tube or intravenous feeding (29.6%), gut symptoms such as diarrhoea (21.3%) and diabetes (13.0%). Overall death rate was 36.1%, with no clear difference between those who had and had not had the probiotic. The authors advise careful watching of critically ill patients given S. boulardii. S. boulardii-linked cases 67.6%; overall mortality 36.1%. (Not in the abstract) Methods, limits and funding Outcomes: Underlying disease, risk factors, treatment and outcome Limitations: A review of published case reports, so it cannot give how common fungemia is. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
Westphal 2026 Saccharomyces boulardii as a Probiotic Supplement in Helicobacter pylori Eradication Therapy: A Meta-analysis. J Gastrointestin Liver Dis · PMID 42470702 · DOI	Systematic review meta analysis	Trials of S. boulardii added to H. pylori eradication treatment (search to October 2024)	Saccharomyces boulardii added to standard H. pylori treatment Capsule or sachet of freeze-dried yeast · vs Same treatment without S. boulardii	Adding S. boulardii significantly raised overall eradication and lowered diarrhoea, nausea and upper-stomach pain. Taste disturbance fell with triple therapy. Bloating, vomiting and rash were not significantly reduced. The authors say more studies are needed for bismuth-based quadruple therapy. Significant but numbers not given in the abstract. (Not in the abstract) Methods, limits and funding Outcomes: H. pylori eradication; side effects Limitations: The abstract gives no numbers. Read from the abstract only. Funding and conflicts: Funding and conflicts not stated in the abstract. Read: abstract
s-fda-preterm-2023 US FDA press release: FDA raises concerns about probiotic products sold for use in hospitalized preterm infants (26 October 2023) · Source	Regulator statement n/a			Methods, limits and funding Read: full-text
s-ncbi-taxonomy NCBI Taxonomy (taxon 4932, Saccharomyces cerevisiae) · Source	Reference database n/a			Methods, limits and funding Read: full-text
s-nccih-probiotics NCCIH (US National Center for Complementary and Integrative Health): Probiotics - Usefulness and Safety (last updated August 2019) · Source	Health agency n/a			Methods, limits and funding Read: full-text
s-nhs-probiotics NHS: Probiotics (page last reviewed 24 November 2022) · Source	Health agency n/a			Methods, limits and funding Read: full-text

What we do not know yet

No trial was read that compares S. boulardii with Lactobacillus rhamnosus GG head to head.
Pregnancy, breastfeeding and yeast allergy were not covered by any source read.
How often fungemia happens per person using the product is unknown.
No study of label accuracy for S. boulardii products was found.
The NIH Office of Dietary Supplements probiotics fact sheet could not be read.
The history of the yeast was not read from a source.

How new research is added

New studies are found by a saved PubMed search and placed in a review queue before the page changes.

Lab markers

What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".

Other 9

●

Chance of antibiotic-associated diarrhoea

Lower in trials

The share of people on antibiotics who get diarrhoea.

Moderate certainty

Results and what it means

Why it was measured

To see whether S. boulardii lowers diarrhoea during antibiotics.

Statistical vs. clinical meaning

A fall in the chance of diarrhoea, which people notice directly.

Safety implication

Rare bloodstream infections have been reported in seriously ill people.

Study	Result	People	Product
¹⁵	Risk 18.7% with control vs 8.5% with S. boulardii (RR 0.47, 95% CI 0.38 to 0.57)	21 trials, 4,780 children and adults on antibiotics	Saccharomyces boulardii vs placebo or no treatment

¹⁵

●

Chance of C. difficile diarrhoea

Lower in trials

The share of people on antibiotics who develop C. difficile diarrhoea.

Low certainty

Results and what it means

Why it was measured

To see whether S. boulardii prevents this infection.

Statistical vs. clinical meaning

The result is clearer in children than in adults.

Safety implication

Rare serious fungemia in severely ill people.

Study	Result	People	Product
¹⁴	S. boulardii RR 0.41 (95% CI 0.22 to 0.79), low certainty	AGA technical review, trials in adults and children on antibiotics	Saccharomyces boulardii vs placebo
¹⁵	Children RR 0.25 (0.08 to 0.73); adults RR 0.8 (0.47 to 1.34), not significant	2 trials in children (579); 9 trials in adults (1,441)	Saccharomyces boulardii vs placebo or no treatment

^{14 15}

●

Return of C. difficile infection

Lower (small trials) in trials

Whether the infection comes back after treatment.

Low certainty

Results and what it means

Why it was measured

To see whether S. boulardii added to treatment cuts recurrence.

Statistical vs. clinical meaning

Both results are from small trials.

Safety implication

Hospital setting; see Safety.

Study	Result	People	Product
⁵	Recurrence 1.7% vs 13.1% (p=0.032); global cure 96.6% vs 85.3% (p=0.044)	120 adults with mild to moderate C. difficile infection	S. boulardii capsules plus vancomycin vs placebo plus vancomycin
¹⁴	Largest earlier trial (124 adults): recurrence of diarrhoea RR 0.59 (0.35 to 0.98), low certainty	AGA review, 5 trials, 223 adults	Saccharomyces boulardii vs placebo with standard antibiotics

^{5 14}

●

How long diarrhoea lasts in children

Shorter in lower-quality trials; no clear change in the best trials in trials

Hours of diarrhoea in a child with gastroenteritis.

Mixed findings

Results and what it means

Why it was measured

To see if S. boulardii shortens an infectious diarrhoea.

Statistical vs. clinical meaning

The two reviews do not agree, and certainty is very low in both.

Safety implication

No serious adverse events were attributed to probiotics in the Cochrane review.

Study	Result	People	Product
¹⁴	About 28.77 fewer hours (95% CI 17.18 to 40.35 fewer), very low certainty	10 trials of S. boulardii in children with gastroenteritis	Saccharomyces boulardii vs placebo or none
⁶	Low-risk-of-bias trials: 8.64 hours shorter, not significant (29.4 shorter to 12.1 longer), very low certainty	6 trials, 3,058 people, all probiotics	Probiotics (many kinds) vs placebo or none

^{14 6}

●

Chance of travellers' diarrhoea

Lower in trials

The share of travellers who get diarrhoea.

Low certainty

Results and what it means

Why it was measured

To see if S. boulardii lowers diarrhoea abroad.

Statistical vs. clinical meaning

Modest drop from few trials.

Safety implication

See Safety for rare infections.

Study	Result	People	Product
¹²	S. boulardii CNCM I-745 RR 0.79 (95% CI 0.72 to 0.87)	6 trials (9 arms) in travellers	S. boulardii CNCM I-745 vs placebo

¹²

●

H. pylori cure rate

Higher in trials

The share of people in whom the H. pylori infection is cleared.

Moderate certainty

Results and what it means

Why it was measured

To see whether S. boulardii adds to standard treatment.

Statistical vs. clinical meaning

A small improvement in cure rate.

Safety implication

Do not replace prescribed treatment.

Study	Result	People	Product
⁴	Adults RR 1.07 (1.03 to 1.10), about +5.7 points, NNT 18; children RR 1.12 (1.03 to 1.23)	19 trials (15 adult, 3 children)	S. boulardii added to eradication therapy vs placebo

^{4 18}

●

Side effects of H. pylori treatment

Lower in trials

Share of people with side effects such as diarrhoea or nausea.

Low certainty

Results and what it means

Why it was measured

To see whether S. boulardii makes treatment easier to finish.

Statistical vs. clinical meaning

The authors rate this low certainty.

Safety implication

Bloating, vomiting and rash were not significantly reduced in another analysis.

Study	Result	People	Product
⁴	19.7% vs 36.0% (RR 0.51, 0.39 to 0.66)	11 trials	S. boulardii added to eradication therapy vs placebo

^{4 18}

●

Abdominal pain in IBS

No clear change in trials

A pain score reported by people with IBS.

Very low certainty

Results and what it means

Why it was measured

To see whether S. boulardii eases IBS pain.

Statistical vs. clinical meaning

No difference from placebo was shown.

Safety implication

Only mild digestive effects in the trials read.

Study	Result	People	Product
¹⁴	SMD 0.26 (95% CI -0.09 to 0.61), very low certainty	3 trials, 232 adults with IBS	S. boulardii vs placebo

¹⁴

●

Relapse of Crohn's disease

No difference in trials

Share of people whose Crohn's disease flares again.

Low certainty

Results and what it means

Why it was measured

To see whether S. boulardii helps people stay in remission.

Statistical vs. clinical meaning

No benefit shown.

Safety implication

Safe and well tolerated in this trial, per the authors.

Study	Result	People	Product
²	Relapse 47.5% vs 53.2%, not significant	165 adults in remission	S. boulardii 1 g a day vs placebo for 52 weeks

Safety

What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.

Main points to know 4

Rare but serious bloodstream infection (fungemia) with this yeast. Cases of Saccharomyces bloodstream infection have been reported after S. boulardii probiotics, mostly in hospital patients. A 2023 review of 108 cases found 67.6% followed S. boulardii use, and common settings were intensive care, tube or intravenous feeding, diarrhoea and diabetes. The overall death rate was 36.1%. A small hospital series found 70% had a central venous line. These reports cannot show how often it happens. Systematic review of case reports and case series ^{17 13 1 21}
Preterm infants: FDA warning. In October 2023 the US FDA warned that probiotic products with live bacteria or yeast can cause invasive, potentially fatal infection in preterm infants in hospital, and that it has not approved any probiotic as a drug or biologic for infants of any age. NCCIH also notes severe or fatal infections in premature infants given probiotics. The warning covers probiotics in general, not S. boulardii alone. Regulator statement ^{19 21}
Weak immune system or serious illness: talk to a doctor first. NCCIH says the risk of harm from probiotics is greater in people with severe illness or weakened immunity, and the NHS says anyone with a weakened immune system or an existing health condition should talk to a doctor before taking probiotic supplements. Authoritative guidance ^{21 22}
What is on the label may not be what is in the product. The NHS says probiotics are classed as food in the UK, so products may not contain the organism or amount stated. NCCIH says some probiotic products have been reported to contain organisms not on the label. Trial results belong to a named strain (usually CNCM I-745). Authoritative guidance ^{22 21}

Side effects 4

Effect	How often	Severity and recovery	Evidence
Mild digestive effects (gas, bloating, nausea, constipation) The AGA technical review reported more constipation with S. boulardii than placebo in one C. difficile trial.	Cochrane reviews of probiotics in general: children 4% vs 6% with any adverse event (probiotic vs control); adults, any adverse event 10.9% vs 12.2% (RR 0.86, 0.72 to 1.01). Common events were rash, nausea, gas, bloating, constipation and cramping. These figures cover all probiotics, not S. boulardii alone.	Usually mild Not stated in the abstracts.	Meta analysis (all probiotics) ^{8 7}
Constipation (S. boulardii specifically) No serious adverse events were reported in the trials in that review.	One trial in the AGA review of C. difficile treatment.	Mild Not stated.	Systematic review of trials ¹⁴
No difference in adverse events in two S. boulardii trials Trials are too small to find rare harms.	Chitapanarux 2025 (120 adults): no significant difference in adverse events and no patient stopped for intolerance. Bourreille 2013 (165 adults): authors called it safe and well tolerated.	Not applicable Not applicable	Randomised trials ^{5 2}
Bloodstream infection with the yeast (fungemia) See the first key warning.	Rare; no frequency found. 108 reported cases in a 2023 review.	Serious; overall death rate 36.1% among reported cases (many were very ill). Treated with antifungal medicine; in one child caspofungin did not work and amphotericin B was used.	Systematic review of case reports ^{17 1}

Liver

No liver injury from S. boulardii was found in the sources read. A liver-safety reference (LiverTox) was not opened for this page.

How often. No frequency was found.

Monitoring. No agency monitoring advice was found.

This is a safety connection. It is not evidence that Saccharomyces boulardii supports liver health.

Medicines and supplements 4

With	Why it matters	Importance	Evidence	What to do
Antibiotics prescription	A 2020 review says the yeast is naturally resistant to antibiotics, which is why it is studied alongside them.	The trials above gave S. boulardii during antibiotic courses. None of the abstracts read reported that it weakened the antibiotic.	Review and trials Low certainty ^{9 15}	Ask the prescriber or pharmacist about timing.
Medicines or conditions that weaken the immune system (for example cancer treatment, steroids, transplant drugs) prescription	Not studied in the sources read; the concern is infection with the live yeast.	NHS and NCCIH advise talking to a doctor first because harm from probiotics is more likely with a weakened immune system.	Authoritative guidance Low certainty ^{22 21}	Ask a doctor before using.
Antifungal medicines prescription	A live yeast could in theory be affected by antifungals.	No source read tested this. One child with a bloodstream infection did not respond to caspofungin.	None found (case report only for treating the infection) Not enough evidence ¹	Ask a pharmacist.
Other probiotics and supplements supplement	Not researched.	No source read.	None found Not enough evidence	Ask a pharmacist.

Who should check first 7

Situation	Advice	Evidence
Critically ill people, people in intensive care, people with a central venous catheter or tube/intravenous feeding	These groups appear most often in fungemia reports. NCCIH says risks should be carefully weighed against benefits for seriously ill hospital patients. A clinician should decide.	Systematic review of cases and authoritative guidance ^{17 13 21}
Preterm and very young infants	FDA warns of invasive, potentially fatal infection with live probiotics in preterm infants in hospital and has not approved any probiotic as a drug for infants of any age.	Regulator statement ^{19 21}
Weakened immune system	NHS: talk to a doctor before taking probiotic supplements.	Authoritative guidance ^{22 21}
Older age	The authors of a small 2021 hospital series suggested older age (80 or more) should be a contraindication for S. boulardii probiotics. This is their opinion from 10 patients, not a regulator rule.	Case series (authors opinion) ¹³
Pregnancy and breastfeeding	No source read covered S. boulardii in pregnancy or breastfeeding, and a LactMed entry was not found. Ask a doctor or midwife.	None found
Children	S. boulardii has been tested in children in trials (for example 6 trials in the 2015 analysis, with a European society recommendation for those on antibiotics with risk factors). The Cochrane review of pediatric trials found no serious adverse events attributed to probiotics. Preterm infants are different, see above. Ask a paediatrician.	Systematic review and guideline ^{15 16 8}
Yeast allergy	Not researched in the sources read.	None found

Overdose, product quality and regulators

Summary. No toxic dose was found in the sources read. The main danger is infection with the live yeast in very ill people, not poisoning.

Animal. Not reviewed.

Overdose response. No source read.

Genotoxicity. Not researched.

Label accuracy and contamination of S. boulardii products were not measured in any study read. Two health agencies describe the general problem for probiotics.

Label may not match contents. The NHS says probiotics are classed as food, so we cannot always be sure a product contains the organism or amount on the label or that it survives to the gut. NCCIH says some products were reported to contain organisms other than those listed, which in some cases may pose serious risks. ^{22 21}

Strain matters. Reviews report results for the named strain, most often S. boulardii CNCM I-745. Other products with the same species name were not shown to give the same results. ^{12 10 14}

Body	Action	Date
NCCIH (US National Center for Complementary and Integrative Health) (United States)	Says risk of harm is greater in people with severe illness or weakened immunity; reports severe or fatal infections in premature infants given probiotics; notes product contents may differ from the label. Names S. boulardii as a yeast used as a probiotic. source	2019-08
NHS (UK) (United Kingdom)	Probiotics are classed as food, not medicine; contents may not match the label; people with a weakened immune system or existing health condition should talk to a doctor first. source	2022-11-24
US Food and Drug Administration (United States)	Warns that live bacteria or yeast products can cause invasive, potentially fatal disease in preterm infants; has not approved any probiotic as a drug or biologic for infants of any age. source	2023-10-26

When to get medical help

Fever or chills in someone in hospital, with a central line, tube feeding or serious illness who has been given a probiotic: this could be a bloodstream infection. Tell the care team at once.
Diarrhoea that is bloody, severe, lasts more than a few days, or comes with a high fever.
Signs of dehydration in a child or older adult (very dry mouth, no urine, unusual sleepiness).
Any new illness in a preterm or very young baby after a probiotic.
Severe allergic reaction (swelling of face or throat, trouble breathing).

Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.

General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.

Frequently asked questions

What is Saccharomyces boulardii?

It is a probiotic yeast sold as a supplement. Most research is on one strain, CNCM I-745. It is a yeast, not a bacterium, so antibiotics do not kill it.

^{9 20}

Does it prevent diarrhoea from antibiotics?

Probably, yes. A 2015 analysis of 21 trials found diarrhoea fell from 18.7% to 8.5%. A European children's group strongly recommends it for children on antibiotics with risk factors.

^{15 16}

Does it help with C. difficile?

The evidence is low certainty. The AGA review found it lowered C. difficile diarrhoea (RR 0.41). In a 2025 trial adding it to vancomycin cut recurrence. It is never a replacement for treatment.

^{14 5}

Does it help children with a stomach bug?

Results are mixed. In the best-designed trials probiotics made little or no difference to diarrhoea lasting 48 hours or more.

^{6 14}

Does it prevent travellers' diarrhoea?

A 2019 analysis of 6 trials found a modest drop (RR 0.79) for the CNCM I-745 strain. The number of trials is small.

¹²

Does it help with H. pylori treatment?

Two 2026 analyses found a small rise in cure rate and fewer side effects when added to standard treatment. It does not treat the infection alone.

^{4 18}

Does it help irritable bowel syndrome?

Evidence is mixed. Three trials found no difference in abdominal pain, and a 2026 review called the results conflicting.

^{14 10}

Does it help Crohn's disease?

A 165-person trial found no benefit for keeping Crohn disease in remission.

Is it safe?

Mild digestive effects were reported in trials, and some trials found no difference from placebo. Rare serious bloodstream infections have been reported, mostly in very ill hospital patients.

^{5 17}

Who should be careful?

People who are seriously ill, in intensive care, have a central line or tube feeding, have a weakened immune system, and preterm infants. Ask a doctor before using it.

^{17 22 19}

Is it the same as yoghurt or baker's yeast?

No. It is a specific yeast product. Foods or other yeasts were not shown to give the same results, and no source read gives a food source for it.

^{20 9}

Is the label reliable?

Not always. The NHS and NCCIH say probiotic contents may not match the label. Check the strain name with a pharmacist.

^{22 21}

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Editorial transparency

Written by: AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
Medical review: None. This page has not been reviewed by a physician or pharmacist.
First published: 2026-10-26
Last substantive update: 2026-10-26
How we research: We started from our existing summary of the yeast, then re-read PubMed abstracts for reviews, guidelines, trials and case reports, the open full text of the AGA technical review, and the NCCIH, NHS and FDA pages. Only abstracts were read for most studies. The NIH Office of Dietary Supplements page was blocked and is marked unread.
How we rate evidence: See "How we rate evidence" in the Evidence tab.
Independence: No product is promoted on this page. No affiliate links are shown. The Cochrane C. difficile review notes probiotic-company links in 28 of its 47 studies.

Sources 22

Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.

Atici S, Soysal A, Karadeniz Cerit K, Yilmaz S, Aksu B, Kiyan G et al.. Catheter-related Saccharomyces cerevisiae Fungemia Following Saccharomyces boulardii Probiotic Treatment: In a child in intensive care unit and review of the literature.. Med Mycol Case Rep. 2017. PMID 28280685. DOI 10.1016/j.mmcr.2017.02.002. (abstract)
Bourreille A, Cadiot G, Le Dreau G, Laharie D, Beaugerie L, Dupas JL et al.. Saccharomyces boulardii does not prevent relapse of Crohn's disease.. Clin Gastroenterol Hepatol. 2013. PMID 23466709. DOI 10.1016/j.cgh.2013.02.021. (abstract)
Bustos Fernandez LM, Man F, Lasa JS. Impact of Saccharomyces boulardii CNCM I-745 on Bacterial Overgrowth and Composition of Intestinal Microbiota in Diarrhea-Predominant Irritable Bowel Syndrome Patients: Results of a Randomized Pilot Study.. Dig Dis. 2023. PMID 36630947. DOI 10.1159/000528954. (abstract)
Chang HK, Shi LB, Song HX, Li P. Saccharomyces boulardii as an Adjunct to Helicobacter pylori Eradication Therapy: A Systematic Review and Meta-Analysis.. J Dig Dis. 2026. PMID 42764401. DOI 10.1111/1751-2980.70071. (abstract)
Chitapanarux T, Wiracha U, Winichakoon P, Salee P, Traisathit P. Efficacy and safety of Saccharomyces boulardii as adjunct therapy with Vancomycin in treating Clostridioides difficile infection: A randomized controlled trial.. Sci Rep. 2025. PMID 40457042. DOI 10.1038/s41598-025-04986-2. (abstract)
Collinson S, Deans A, Padua-Zamora A, Gregorio GV, Li C, Dans LF et al.. Probiotics for treating acute infectious diarrhoea.. Cochrane Database Syst Rev. 2020. PMID 33295643. DOI 10.1002/14651858.CD003048.pub4. (abstract)
Esmaeilinezhad Z, Ghosh NR, Walsh CM, Steen J, Burgman A, Mertz D et al.. Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children.. Cochrane Database Syst Rev. 2025. PMID 40931979. DOI 10.1002/14651858.CD006095.pub5. (abstract)
Guo Q, Goldenberg JZ, Humphrey C, El Dib R, Johnston BC. Probiotics for the prevention of pediatric antibiotic-associated diarrhea.. Cochrane Database Syst Rev. 2019. PMID 31039287. DOI 10.1002/14651858.CD004827.pub5. (abstract)
Kazmierczak-Siedlecka K, Ruszkowski J, Fic M, Folwarski M, Makarewicz W. Saccharomyces boulardii CNCM I-745: A Non-bacterial Microorganism Used as Probiotic Agent in Supporting Treatment of Selected Diseases.. Curr Microbiol. 2020. PMID 32472262. DOI 10.1007/s00284-020-02053-9. (abstract)
Maslennikov R, Gosteeva E, Ananeva V, Korshunova L, Kravtsowa A, Poluektova E et al.. Strain-Specific Systematic Review with Meta-Analysis of Probiotics Efficacy in the Treatment of Irritable Bowel Syndrome.. J Clin Med. 2026. PMID 41682832. DOI 10.3390/jcm15031152. (abstract)
McFarland LV. Systematic review and meta-analysis of Saccharomyces boulardii in adult patients.. World J Gastroenterol. 2010. PMID 20458757. DOI 10.3748/wjg.v16.i18.2202. (abstract)
McFarland LV, Goh S. Are probiotics and prebiotics effective in the prevention of travellers' diarrhea: A systematic review and meta-analysis.. Travel Med Infect Dis. 2019. PMID 30278238. DOI 10.1016/j.tmaid.2018.09.007. (abstract)
Poncelet A, Ruelle L, Konopnicki D, Miendje Deyi V, Dauby N. Saccharomyces cerevisiae fungemia: Risk factors, outcome and links with S. boulardii-containing probiotic administration.. Infect Dis Now. 2021. PMID 33934809. DOI 10.1016/j.idnow.2020.12.003. (abstract)
Preidis GA, Weizman AV, Kashyap PC, Morgan RL. AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders.. Gastroenterology. 2020. PMID 32531292. DOI 10.1053/j.gastro.2020.05.060. (full-text)
Szajewska H, Kolodziej M. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea.. Aliment Pharmacol Ther. 2015. PMID 26216624. DOI 10.1111/apt.13344. (abstract)
Szajewska H, Canani RB, Guarino A, Hojsak I, Indrio F, Kolacek S et al.. Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Children.. J Pediatr Gastroenterol Nutr. 2016. PMID 26756877. DOI 10.1097/MPG.0000000000001081. (abstract)
Vinayagamoorthy K, Pentapati KC, Prakash H. Epidemiology of Saccharomyces fungemia: A systematic review.. Med Mycol. 2023. PMID 36806741. DOI 10.1093/mmy/myad014. (abstract)
Westphal JR, Koch N, Vilchez-Vargas R, Vasapolli R, Malfertheiner P, Schulz C. Saccharomyces boulardii as a Probiotic Supplement in Helicobacter pylori Eradication Therapy: A Meta-analysis.. J Gastrointestin Liver Dis. 2026. PMID 42470702. DOI 10.15403/jgld-6797. (abstract)
. US FDA press release: FDA raises concerns about probiotic products sold for use in hospitalized preterm infants (26 October 2023). . . (full-text)
. NCBI Taxonomy (taxon 4932, Saccharomyces cerevisiae). . . (full-text)
. NCCIH (US National Center for Complementary and Integrative Health): Probiotics - Usefulness and Safety (last updated August 2019). . . (full-text)
. NHS: Probiotics (page last reviewed 24 November 2022). . . (full-text)

Where to buy

Check the label first. Whatever you buy, look for these:

The amount of the active ingredient per serving, not just the front-label claim
A third-party testing mark (USP, NSF or ConsumerLab)
Other ingredients and allergens
Ask a pharmacist about interactions with your medicines

Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.

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Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.