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S. boulardii Review, Proven Benefits and Safety Issues

Updated 2/2/2021

Medically Reviewed by Dr. Atmika Paudel, PhD - Written by Dan Jackowiak Nc, HHP and Dr. Vibhuti Rana, PhD

Dr. Atmika Paudel, PhD says... The article below about Saccharomyces boulardii's benefits and health risks is medically correct.

Saccharomyces boulardii or S. boulardii has been used for the last 30 years or so to treat antibiotic associated diarrhea with pretty good results. It has also been used to treat diarrhea caused by Clostridium difficile and Traveler's diarrhea. Numerous clinical studies have been run to see if it works for Crohn's disease, Helicobacter pylori, ulcerative colitis, irritable bowel syndrome, parasitic infections and HIV-related diarrhea. It's also been used to treat Candida yeast infections and I am going to get into those results in a little bit.

Although Saccharomyces boulardii is classified as a probiotic, it is not a bacteria; it is a yeast. It was first isolated from lychee and mangosteen fruit in 1923 by French scientist Henri Boulard. Since then, it has been genome mapped and is now classified as a subspecies of the yeast Saccharomyces cerevisiae, with over 99% genome relatedness. It is nearly identical to the Saccharomyces cerevisiae strains that are used to make wine and beer.(1)

S. boulardii's Medically Proven Benefits

Luckily, a comprehensive study was published in Therapeutic Advances in Gastroenterology in 2012 that we can refer too, to see just how effective S. boulardii is for intestinal problems. (2)

  • First up is antibiotic associated diarrhea, AAD, that often occurs when taking antibiotics. In 10 controlled trials, an 80% reduction in symptoms was observed among patients. It also demonstrated an ability to prevent AAD in 30% of adults and children.
  • It had a positive effect on acute and persistent diarrhea due to a variety of causes as well. The outcomes for children showed a 50% success rate in reducing the condition.
  • Travelers diarrhea is often associated with unsanitary food handling conditions in many of the third world countries. S. boulardii achieved an 11% reduction in this illness in 12 clinical trials.
  • Sometimes taking antibiotics can trigger an over growth of Clostridium difficile, a pathogenic bacteria that often kills older adults. Saccharomyces boulardii was found in two clinical trials to reduce the chronic diarrhea that is associated with this infection up to 33%.
  • Fourteen clinical trials involving 1671 patients being treated for H. pylori revealed an improvement in treatment related side effects and success rates. It decreased the risk of triple antibiotic associated diarrhea and induced cell death in the bacteria improving the success rate for treatment by 9%.
  • In patients with Crohn's disease, it helped reduce colon permeability and prevented a relapse after treatment in 38% of the patients.
  • A recent analysis of 20 clinical trials involving S. boulardii and 1404 subjects with Irritable bowel syndrome, showed the quality of life was improved but it did not improve intestinal symptoms.
  • S. Boulardii seems to have a beneficial effect in amebiasis, giardiasis and infection with Blastocystis homini. It helped enhance the clearance of amebic colitis when taken with antibiotics. It also helped reduce the patients diarrhea, abdominal pain and fever. It improved treatment success rates for giardia and Blastocystis hominis.
  • It improved diarrhea often associated with HIV positive patients by 61%.
  • However, the study also pointed out that there have been over 100 cases of infection by S. boulardii in immunocompromised patients. Some of these patients took it by mouth; and some were infected through their iv catheters, they suspect infection occurred when opening the packet and the spores became airborne.(2)

Numerous studies have been carried out using Saccharomyces boulardii and various species of Candida including Candida albicans and Candida glabrata.(3,4,5,6,7,8)

All of these published scientific studies came to the same conclusion, S. boulardii does not kill Candida yeast.

It does however secrete capric acid like what is found in coconut oil. This helps to prevent candida yeast from forming hyphae and building biofilms. It also helps reduce the spread of the candida colony by preventing it from adhering to epithelial cells. It helps reduce cytokine-mediated inflammatory host response and therefore reduces inflammation. 

Lyophilized preparations, which have to be refrigerated, performed much better in these clinical studies than freeze dried forms. Doses need to be at least 500mgs or more to have any success.

Dr. Vibhuti Rana, PhD says...

S. boulardii is considered as a subtype of S. cerevisiae and has implications in the baking and brewery industries. More importantly, it has been used as an indispensable yeast probiotic for handling several gastrointestinal health issues like diarrhea, irritable bowel syndrome, Crohn’s disease, etc (1).

Better acid and heat tolerance as compared to makes it better suited for the gut environment. Found over 100 years ago from the peels of some fruits, it is now available as an over the counter probiotic. In a study conducted in 2016 some hamsters were infected with Clostridium difficile strains which led to cecal inflammation, mucous membrane damage, and increased expression of TNF Alpha and NF Kappa B phosphorylation - activating the host inflammatory pathways. When S boulardii was administered to these hamsters it showed great improvement in the damage caused(2).

Moreover infections of the gastrointestinal tract caused by Clostridium dificile and Helicobacter pylori when treated with antibiotics may lead to real complications. In a meta data analysis, S. boulardii based probiotics have been shown to effectively prevent diarhea which is associated with the antibiotic usage (3).

In a study done on oncohemalogical patients suffering from acute myeloid leukemia, myelodysplastic syndrome, or multiple myeloma, preparations of S. boulardii based probiotics did not cause any sepsis (4).

It has also been discussed that the frequency of the gene transfer of the antibiotic resistant genes is quite less between yeast and bacteria as compared to between two bacterial strains. So, it is not only stress resistant but also resistant to antibiotic actions. Also, S. boulardii is referred as generally regarded as safe (GRAS) with probiotic activity against a number of gut pathogens (5).

1. Sen, S., Mansell, T.J., Yeasts as probiotics: mechanisms, outcomes, and future potential, Fungal Genetics and Biology (2020), doi:

2. Koon HW, Su B, Xu C, Mussatto CC, Tran DH, Lee EC, Ortiz C, Wang J, Lee JE, Ho S, Chen X, Kelly CP, Pothoulakis C. Probiotic Saccharomyces boulardii CNCM I-745 prevents outbreak-associated Clostridium difficile-associated cecal inflammation in hamsters. Am J Physiol Gastrointest Liver Physiol. 2016 Oct 1;311(4):G610-G623. doi: 10.1152/ajpgi.00150.2016. Epub 2016 Aug 11. PMID: 27514478; PMCID: PMC5142203.

3. Videlock EJ, Cremonini F. Meta-analysis: probiotics in antibiotic-associated diarrhoea. Aliment Pharmacol Ther. 2012 Jun;35(12):1355-69. doi: 10.1111/j.1365-2036.2012.05104.x. Epub 2012 Apr 24. PMID: 22531096.

4. Sulik-Tyszka, B., Snarski, E., Niedźwiedzka, M. et al. Experience with Saccharomyces boulardii Probiotic in Oncohaematological Patients. Probiotics & Antimicro. Prot. 10, 350–355 (2018).

5. Al-zaidi et al, Eukaryotic Probiotic Saccharomyces boulardii Application in Clinical Trails: A Review, IJPQA, Volume 11 Issue 1 Jan 2020 – Mar 2020,,Vol11,Issue1,Article25.pdf

Is Saccharomyces Boulardii Safe to Take?

In 2003, an article was printed in the Journal of Clinical Microbiology describing outbreaks of Saccharomyces cerevisiae subtype boulardii in four hospitalized patients that were in the vicinity of patients that were treated with this yeast. All four were infected from the iv's that had been placed in their bodies. The suspected cause was that the yeast became airborne or the workers hands transferred the yeast to the patient in spite of repeated washing of their hands. All four patients recovered after being given 400mgs of fluconazole for various time frames.

The article points out that "Fungemias are not limited to immunocompromised patients and for this reason, S. cerevisiae subtype boulardii should be considered a potentially dangerous microorganism." (9)

In 2015, an article was published in Frontiers of Microbiology that talks about the potential risks of opportunistic strains of Saccharomyces cerevisiae in food products. They admit that S. cerevisiae has an impeccably good food safety record but the large amounts of this yeast that people are consuming these days is cause for concern.

They said that S. boulardii is nothing other than the commercialized name for S. cerevisiae and that S. cerevisiae has been related to a wide variety of infections, which range from vaginitis infections in healthy patients and cutaneous infections, to systemic bloodstream infections and infections of essential organs in immunocompromised and critically ill patients.(10)

I have a stack of stool test results from people with very high levels of Saccharomyces cerevisiae with no other yeasts present. These people are infected and are not immunocompromised laying in a bed in an Intensive Care Unit. Just the fact that the article in Frontiers of Microbiology mentions, "vaginitis infections in healthy patients", would keep me from taking it. Especially when you consider that it does not kill candida!

Yes, it keeps it from spreading but so does Gymnema sylvestre, which also has the ability to cause hypheal forms of yeast to shift back to a spore form which is easier to kill. And, because the effective agent it secretes, capric acid, is also in coconut oil, why not remove the risk and just take coconut oil, which is a food and has been medically proven to kill yeast.

Medical Review by Dr. Atmika Paudel, PhD

The above article about Saccharomyces boulardii and the facts given in the article have been provided with evidences are correct. Probiotics actually are the live microorganisms, including bacteria and yeast, that have beneficial role to health.(1)

As mentioned in the article above, S. boulardii have shown many beneficial effects to human health and much more recent studies have been done regarding the use of S. boulardii. To give an example: a recent randomized controlled clinical trial was showed that S. saccharomyces was able to reduce the imbalance and alteration caused by the antibiotic treatment for the Helicobacter pylori, a known causative agent of chronic gastritis and gastroduodenal ulcer.(2)

It plays a crucial role in the preservation and/or restoration of intestinal barrier function in multiple disorders. S. boulardii has also been shown to have beneficial effects in the treatment of blastocystosis.(3)

A recent review paper has highlighted the use of S. boulardii in the possible treatment of colorectal cancer (4)

However, due to some cases of systemic infection in immunocompromised as well as otherwise healthy people, and as mentioned in the above article, S. boulardii should be used with caution and more clinical trials are needed.

1. CZERUCKA, D., PICHE, T. and RAMPAL, P. (2007), Review article: yeast as probiotics –Saccharomyces boulardii. Alimentary Pharmacology & Therapeutics, 26: 767-778. doi:10.1111/j.1365-2036.2007.03442.x
2. Oh, B., Kim, B.‐S., Kim, J.W., Kim, J.S., Koh, S.‐J., Kim, B.G., Lee, K.L. and Chun, J. (2016), The Effect of Probiotics on Gut Microbiota during the Helicobacter pylori Eradication: Randomized Controlled Trial. Helicobacter, 21: 165-174. doi:10.1111/hel.12270
3. Clinical efficacy of Saccharomyces boulardii or metronidazole in symptomatic children with Blastocystis hominis infection. Parasitology Research, 2011, Volume 108, Number 3, Page 541 Ener Cagri Dinleyici, Makbule Eren, Nihal Dogan,
4. An overview of yeast probiotics as cancer biotherapeutics: possible clinical application in colorectal cancer. Shamekhi, S., Lotfi, H., Abdolalizadeh, J. et al. Clin Transl Oncol (2020).

Saccharomyces Boulardii is available here if you really want to take it.

You can find out more about S. boulardii here.

Back to Best Probiotics For Yeast Infections

Any questions about S. boulardii or any other questions or concerns, please feel free to contact us through the contact page of this website or see your doctor.


Article References

1. Sci Rep. 2017; 7: 371. PMCID: PMC5428479. Complete genome sequence and comparative genomics of the probiotic yeast Saccharomyces boulardii
2. Therap Adv Gastroenterol. 2012 Mar; 5(2): 111–125. Efficacy and safety of the probiotic Saccharomyces boulardii for the prevention and therapy of gastrointestinal disorders
3. J Infect Dis. 1993 Nov;168(5):1314-8.Inhibition of Candida albicans translocation from the gastrointestinal tract of mice by oral administration of Saccharomyces boulardii.
4. FEMS Microbiology Letters, Volume 310, Issue 1, 1 September 2010, Pages 17–23, The effect of Saccharomyces boulardii on Candida albicans-infected human intestinal cell lines Caco-2 and Intestin.
5. Plos One. Published: August 10, 2010. Capric Acid Secreted by S. boulardii Inhibits C. albicans Filamentous Growth, Adhesion and Biofilm Formation.
6. Med Mycol. 2007 Dec;45(8):691-700. Saccharomyces boulardii decreases inflammation and intestinal colonization by Candida albicans in a mouse model of chemically-induced colitis.
7. Med Mycol. 2016 Nov 1;54(8):835-45. doi: 10.1093/mmy/myw026. Epub 2016 Jun 1. Probiotic yeast Saccharomyces boulardii (nom. nud.) modulates adhesive properties of Candida glabrata.
8. FEMS Yeast Res. 2009 Dec;9(8):1312-21. 2009 Aug 5. The antagonistic effect of Saccharomyces boulardii on Candida albicans filamentation, adhesion and biofilm formation.
9. J. Clin. Microbiol. November 2003. Outbreak of Saccharomyces cerevisiae Subtype boulardii Fungemia in Patients Neighboring Those Treated with a Probiotic Preparation of the Organism.
10. Front Microbiol. 2015; 6: 1522. Published online 2016 Jan 8. Opportunistic Strains of Saccharomyces cerevisiae: A Potential Risk Sold in Food Products

Intensive Care Med. 2002 Jun;28(6):797-801. Epub 2002 May 10. Seven cases of fungemia with Saccharomyces boulardii in critically ill patients.

Medical Mycology Case Reports, Volume 18, December 2017, Pages 15-17. Saccharomyces cerevisiae var. boulardii fungemia following probiotic treatment.

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