Saccharomyces boulardii
A probiotic for world travelers and individuals on courses of antibiotics.
I’m often asked how to prevent digestive upset while traveling to unfamiliar places—beyond the usual advice about safe food and filtered water. Another common question: what probiotic can help support gut health during a course of antibiotics?
Enter Saccharomyces boulardii.
S. boulardii is a non-pathogenic probiotic yeast used to support digestive and immune function. Unlike bacterial probiotics, S. boulardii can survive the harsh environment of the stomach and reach the intestines intact, where it provides temporary colonization to help maintain microbial balance.
It is particularly well-regarded for its role in supporting gastrointestinal function during travel, periods of antibiotic use, and episodes of acute digestive disruption.
A Brief History of Discovery
This probiotic yeast was first isolated in the 1920s by French microbiologist Henri Boulard, who observed that people in Southeast Asia used the skins of lychees and mangosteens to manage diarrhea. Boulard successfully isolated the active yeast and named it Saccharomyces boulardii in recognition of his work. Since then, it has been studied extensively for its beneficial effects on gastrointestinal health in both adults and children.
How Is S. boulardii Produced?
S. boulardii is grown in sterile, controlled environments using nutrient-rich substrates, often derived from tropical fruit. After cultivation, the yeast is harvested, freeze-dried to preserve its viability, and encapsulated.
As with any probiotic, strain quality and manufacturing standards matter—choosing a reputable, evidence-based brand ensures the supplement delivers its intended benefits.
Travel-Related Digestive Support
S. boulardii has been studied for its ability to reduce the incidence and duration of traveler’s diarrhea, often caused by exposure to unfamiliar foods or microbial contamination. Clinical trials have shown it may help maintain intestinal stability during travel to high-risk areas.
Support for Gut-Associated Immune Function
This yeast probiotic has immunomodulatory effects that may enhance the gut’s immune response to pathogens. It does so without overstimulating the immune system, making it a useful tool for bolstering local immune defense in the gastrointestinal tract.
Protection of the Gut Barrier
Research indicates S. boulardii supports the structural integrity of the intestinal lining and may reduce intestinal permeability — aka “leaky gut.”
S. boulardii and Antibiotics
Antibiotics can disrupt the balance of the gut microbiota, often leading to side effects such as bloating, diarrhea, or discomfort. Many bacterial probiotics are ineffective when taken alongside antibiotics due to susceptibility to the drugs.
However, because S. boulardii is a yeast, it is not affected by antibiotics, making it one of the few probiotics that can be taken concurrently with antibiotic therapy.⁴ Clinical trials support its use in reducing the risk of antibiotic-associated diarrhea and promoting recovery of the microbiome.
Safety Considerations
While S. boulardii is generally well tolerated, there are important considerations for certain populations:
Immunocompromised Individuals should consult their healthcare provider before using probiotic supplements, including yeast-based strains.
Yeast Sensitivity or Allergy: While S. boulardii is a beneficial yeast, individuals with a true allergy to yeast (such as Saccharomyces cerevisiae) should consult their healthcare provider before use. It's important to note that S. boulardii is genetically and functionally distinct from Candida species, which are opportunistic yeasts commonly associated with overgrowth in the gut. Individuals with active Candida infections or concerns about yeast overgrowth should work with a knowledgeable practitioner to determine if S. boulardii is appropriate.
Pregnancy, Breastfeeding, and Pediatrics: Always consult a healthcare provider before use during pregnancy or when giving to young children. At least one study shows that it may provide relief from acute childhood diarrhea.
Use with Antifungal Medications: As an active yeast, S. boulardii may be inactivated by antifungal medications.
The Bottom Line
Whether you're traveling, using antibiotics, or looking to support gut resilience more generally, Saccharomyces boulardii offers a well-researched, natural option for digestive support. Its unique resilience, immune-modulating properties, and track record in clinical studies make it a valuable tool in any gut health strategy.
