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Bacteria

Saccharomyces boulardii

Saccharomyces boulardii is a probiotic yeast, a strain of Saccharomyces cerevisiae first isolated from tropical fruit.

Immune SupportGut Health

What it is studied for

The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.

DiarrheaStrongA3 studies
Travel SupportImmune SupportStrongA3 studies
Gut healthStrongA3 studies
Microbiome healthGut HealthStrongA3 studies
Immune SupportModerateA3 studies
Bloating & gas reliefGut HealthModerateBNo linked study
All 9 rated effectsGrouped by health goal, with the publications behind each rating

A probiotic yeast with a specific job

Saccharomyces boulardii is a yeast used as a probiotic, unlike the bacteria in many other probiotic products. Most of its clinical research concerns particular forms of diarrhea, rather than a general improvement in digestion. 1

How could it help the gut?

Laboratory and animal research suggests several routes, including enzymes that break down bacterial toxins and effects on intestinal barrier and immune signaling. These mechanisms help explain why researchers test the yeast; they do not establish that every proposed action produces a benefit in people. 1

Key studies

The most recent publications linked to Saccharomyces boulardii's ratings.

Investigating the Efficacy of Saccharomyces boulardii in Metabolic Syndrome Treatment: A Narrative Review of What Is Known So Far2023Impact of probiotic Saccharomyces boulardii on the gut microbiome composition in HIV-treated patients: A double-blind, randomised, placebo-controlled trial2017Influence of Saccharomyces boulardii CNCM I-745on the gut-associated immune system2016Saccharomyces boulardii CNCM I-745 supports regeneration of the intestinal microbiota after diarrheic dysbiosis – a review2015Efficacy and Safety of Saccharomyces boulardii for Acute Diarrhea2014
All 10 studiesEvery publication linked to Saccharomyces boulardii

Why people take it

Immune Support26.3%
Gut Health26%
Essential Health22%
Detox12.7%
Inflammation4%
Energy2.3%

SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.

Questions people ask

Is it a bacterium?

No. It is a probiotic yeast. 1

Does it prevent C. difficile infection?

The 2015 review did not find a significant preventive effect for C. difficile-associated diarrhea in adults; the pediatric result came from only two trials. 2

Can it replace rehydration?

No. Fluid and electrolyte replacement remains central when treating diarrhea. 3

When does diarrhea need medical assessment?

The German leaflet flags diarrhea lasting longer than two days, blood in the stool or fever. 4

Is it safe during pregnancy?

The German medicinal-product leaflet advises against use because appropriate evidence is lacking. 4

Sources