The Four Benefits of Probiotic Saccharomyces boulardii (S boulardii)

by , | December 3, 2023 | Articles, Gut Health


Bojana Jankovic Weatherly, MD, MSc, FACP, IFMCP and Erica Gittleson, RD

What is S boulardii?

S boulardii is a non-pathogenic (non disease-causing) yeast considered to be a probiotic that was isolated in 1920 by Henri Boulard. He observed that individuals who ingested lychee and mangosteen tea didn’t develop symptoms of cholera (1, reviewed in 6). 

1. S. Boulardii Reduces the Risk of Antibiotic Associated Diarrhea

S boulardii exerts antimicrobial activity and can affect the gut microbiome (bacteria and other organisms residing in the gut) through multiple mechanisms. Antibiotics can adversely affect the gut microbiome. Antibiotic-associated diarrhea (AAD) is a common complication of antibiotic use. AAD is defined as diarrhea that is associated with antibiotic administration and is not explained by another process. Any antibiotic can cause AAD as early as just a few hours following antibiotic administration up to several months after its discontinuation. As noted in our previous article, taking probiotics with antibiotics can reduce the risk of antibiotic-associated diarrhea and help balance your gut microbiome (2). In a systematic review with meta-analysis, 21 randomized controlled trials (4780 participants – adults and children), were analyzed.  Administration of S. boulardii compared with placebo or no treatment reduced the risk of antibiotic-associated diarrhea in patients treated with antibiotics from 19% to 9%.  This means that for every 10 patients receiving daily S. boulardii with antibiotics, one fewer would develop diarrhea. This benefit was slightly more pronounced in children compared to adults. It’s also noted in the study that S. boulardii significantly reduced the risk of Clostridium difficile (C. diff) associated diarrhea among children, but not adults (3).   

An important strength of the study is the methodology developed by the Cochrane Collaboration, including use of methods to reduce bias (i.e., comprehensive literature search, pre-specified criteria for methodological assessment and analysis, no restrictions by language or year of publication). One major limitation, however, is that the quality of the included trials varied. Only two trials were at low risk of bias. Some of the sources of bias in the remaining trials included unclear randomization process, unclear or lack of blinding, unclear or no blinding of outcome assessment, and selective or unclear reporting. Another important limitation is the difference in how diarrhea was defined in the included trials in that duration and follow-up of diarrhea varied. Finally, some of the clinical trials had a small sample size. The authors note that the total sample size in the meta-analysis, however, was sufficient to draw conclusions (3).  

How Should I Take Probiotics if I’m Taking Antibiotics?

It’s important that probiotics be taken at least a few hours after taking antibiotics, so as not to negate the effect of probiotics. Therefore, if you take your antibiotic with breakfast at 9am, wait until at least 12pm to take your probiotic. If the probiotic contains only S boulardii (a yeast) and no bacterial strains, it can be taken at the same time as the antibiotic, since S Boulardii is resistant to antibiotics.

2. S boulardii Affects Gut Motility

Another benefit of S. boulardii is that it can slow down gut motility and relieve IBS symptoms. In one animal study, S.bouldardii was found to upregulate serotonin transporter (SERT) in colon cells of mice. Serotonin is a neurotransmitter that promotes intestinal motility. Serotonin transporter takes it up, once released. As a result of causing greater serotonin uptake, S. Boulardii treatment decreased the defecation parameters and slowed the bowel transit in mice (4). 

3. S boulardii May Affect Colitis

Another promising benefit of S. boulardii is the management of relapsing colitis. S boulardii plays a role in immune modulation at the level of the gut and can suppress pro-inflammatory signaling. This study examined the treatment of colitis in mice using S. boulardii in conjunction with the antibiotic doxycycline. The findings showed that these two agents together reduced intestinal inflammation. This was evidenced by a reduced disease activity index, colonic tissue damage and expression of inflammatory mediators. The study supports the potential benefit of S. Boulardii in the treatment of colitis (5). 

4. S boulardii Can Influence Metabolism

S. Boulardii has also shown promise in metabolic syndrome. Metabolic syndrome is characterized by complex metabolic changes involving a cluster of co-occurring conditions. Three or more of the following signs suggest metabolic syndrome: large waistline, high blood pressure, high blood glucose, high blood triglycerides, and low HDL cholesterol levels. A review of 8 studies (3 human) points to S. boulardii’s positive effect on the lipid profile, modulation of the intestinal microbiota, human gene expression related to cholesterol absorption and a decrease in weight gain. Although more research is needed to validate these results, especially in humans, there is a trend toward improvement in metabolic syndrome and a reduction in its risk factors with the administration of S. boulardii (6).  

5. Dosing

Daily dose of S. boulardii that has been studied varies widely. Until we have more precise data regarding S. boulardii dosing, a typical daily dose for adults is 500-1000mg/day (10-20 billion colony forming units (CFUs)) in the context of AAD prevention and metabolic syndrome studies. The typical dose for children is 250-500mg in RCTs of AAD prevention. 

6. Safety

S. boulardii is considered to be safe and well tolerated, however it can cause fungemia (a serious infection characterized by presence of fungi or yeast in the blood that can be life threatening) in individuals with severe bowel disease, those who are immunocompromised or those who have a catheter. It is therefore important that anyone with potential risk factors discuss risks vs benefits of use with their qualified healthcare provider. 

Talk to your qualified healthcare practitioner to determine if you should start taking probiotics and which ones are right for you.  

If you are dealing with gut issues, autoimmune conditions or other chronic disease, and wish to explore an integrative, evidence-informed approach, feel free to reach out to us at and we would be happy to schedule a discovery call. 


  1. Saccharomyces boulardii: What Makes It Tick as Successful Probiotic? – PMC (
  2. Should I Take Probiotics When Taking Antibiotics? – Dr. Bojana (
  3. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea – PubMed (
  4. Saccharomyces boulardii, a yeast probiotic, inhibits gut motility through upregulating intestinal serotonin transporter and modulating gut microbiota – PubMed (
  5. A new therapeutic association to manage relapsing experimental colitis: Doxycycline plus Saccharomyces boulardii – PubMed (
  6. Investigating the Efficacy of Saccharomyces boulardii in Metabolic Syndrome Treatment: A Narrative Review of What Is Known So Far – PubMed (


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