In the world of natural health, yeasts get a bad rap. But one of my favorite probiotics, Saccharomyces boulardii, is actually a beneficial medicinal yeast!


Commonly referred to as S. Boulardii, it was originally found on lychee fruit in the 1920s. When taken as an oral supplement, it colonizes the gut within three days. But the colonization is temporary—S. Boulardii disappears from stool within five days of discontinuing supplementation. Interestingly, the health benefits that it provides last beyond the time of oral consumption—which means that, like most other probiotic supplements—the benefits are not due to the probiotic strains taking root and colonizing.

Used for prevention and treatment of diarrhea

Many types of diarrhea are caused by dysbiosis (bad organisms living in the gut). When this occurs, the healthy microbial population takes a significant nose dive–especially important species like Bacteriodies, Ruminococus and Prevotella.

At the same time, the gap formed by the notable decrease in these beneficial bacteria, creates a void-like vulnerability that allows for increases in opportunistic bacteria like Enterobacter and less desirable Clostridia strains—these are aptly referred to as “pioneer bacteria” because they migrate to an area when there is an opportunity!

In this situation,  Saccharomyces Boulardii has been shown to help in several ways:

  1. S Boulardii actually helps to bind pathogenic bacteria and carry them out of the digestive tract, especially Staphylococcus aureus, Klebsiella, Candida, and Salmonella
  2. Several human studies have demonstrated that S boulardii supplementation leads to faster re-establishment of a healthy microbiome, when recovering from infectious diarrhea.
  3. It increases the population of specific types of bacteria that are known to produce short chain fatty acids (SCFAs) by fermenting dietary fibers (prebiotics) and resistant starch.  SCFAs are the energy substrate of cells in the gut lining that allow it to constantly heal and regenerate, preventing Leaky Gut. They also directly support some of the commensal (or good) bacteria as well.

S Boulardii is most notably useful in infectious Clostridium difficile infection. Clostridium Difficile (also called “C Diff”) is the primary cause of acute diarrhea after antibiotics, and it not an infection to take lightly. In extreme cases, it can even be life threatening. When 124 patients on high dose vancomycin (an antibiotic) for C. difficile related colitis were given S. boulardii, rates of recurrence plummeted from 50% to 16.7%.

But bacteria are not the only micro-organisms that can cause diarrhea. Overgrowth of yeasts like Candida Albicans can also induce diarrhea by causing inflammation of the gut lining.  S boulardii  has been shown to decrease tissue inflammation in the gut caused by colitis from Candida overgrowth, alleviating diarrhea from this cause.

Disrupts candida colonization in vaginal and other tissues

Candida albicans is the most common opportunistic fungal pathogen found in the human body.  It has many tools at its disposal that allow it to thrive and take root; the ability to adhere to tissues and even penetrate them, biofilm formation and the ability to transformation into different forms at various stages of its life cycle.

In order to get an overgrowth in the first place, adherence is the first necessary step. Candida albicans is capable of adhering to the inside of cheeks, labia,  vaginal and intestinal epithelial cells, as well as catheters, dental implants or artificial joints.

Not only has it been shown to interrupt Candida’s adherence, but S. boulardii is uniquely able to stimulate Secretory IgA (SIgA), our first line of defense against invading microbes.  SIgA is essential to maintaining intestinal mucosal integrity, preventing leaky gut, and ensuring a stable, diverse microbiome—which is key to bulletproofing your gut. This is the main immune agent found in  mucous membranes, saliva, tears and vaginal secretions, as its main function is to help protect you against pathogens.


Perhaps the best use of S Boulardii is prophylactically.

With Antibiotic use: Since it yeast are not killed by antibiotics (only bacteria are susceptible to antibiotic drugs) you can (and should) take S boulardii during antibiotic therapy to prevent Candida overgrowth and other diarrhea-inducing opportunistic pathogens.  Several studies have demonstrated that in patients with known H. pylori infection, S Boulardii supplementation improved eradication rates and reduced treatment-related side effects.

You can also take it before, during, and after travelling—it helps prevent traveler’s diarrhea! Meta-analysis of probiotics used preventatively for travelers diarrhea all showed significant reduction in the risk of traveler’s diarrhea when probiotics are used—but two randomized control trials showed a significant reduction in traveler’s diarrhea in the S. boulardii group compared with other types of probiotics used as controls.

For this particular purpose, I suggest 1000 mg daily.  Should you get sick while travelling, you can continue to take it during traveler’s diarrhea, or ongoing diarrhea, to shorten the duration and promote recovery.

A word of caution

S Boulardii has been shown in studies to be helpful helping improve symptoms of Crohn’s disease, ulcerative colitis, and irritable bowel syndrome. For example, in a 6-month study of patients with Chrons Disease, the relapse rate was significantly lower in patients treated with mesalazine plus S. boulardii (6%) than in those treated with mesalazine alone (38%).

That said, in my clinical experience, people with Inflammatory bowel disease should proceed with caution, when initially introducing S boulardii.  The reason for this Anti-Saccharomyces cerevisiae antibodies (ASCA) have been associated with Crohn’s disease (CD). Saccharomyces Cervisiae (Brewer’s/Bakers yeast)—used in baking as well as in brewing beer and wine—is similar enough to Saccharomyces Boulardii that  the immune systems of sensitive individuals can cross react, potentially triggering a symptom flare. If any flare in symptoms is noted with oral consumption, discontinue use. Like other probiotics, S boulardii is also not appropriate in severely immunocompromised individuals.

To buy Saccharomyces Boulardii, click here!Floramyces

Have you ever used this probiotic yeast for your gut health? What was your experience?