Ingredient review

Saccharomyces boulardii


What is it?

Saccharomyces boulardii (S. boulardii) is a non-pathogenic yeast microbe with properties that protect it against antibiotics, the body’s internal temperatures, and the acidic environments of the gastrointestinal tract. These properties are not typically observed with bacterial probiotics. (2)(9) S. boulardii was first discovered in lychee and mangosteen fruit and is now cultivated for use in supplements as lyophilized powders, capsules, or liquid beverages. (5

Not to be confused withSaccharomyces cerevisiae (7)

Download ingredient review

Main uses

Gastrointestinal disorders
Parasitic infections


Labels typically indicate the requirement of refrigeration to prevent loss of potency (7)
Stable at room temperature if kept free from moisture (7)
May have better survival against bile and stomach acid (4)

Dosing & administration

Adverse effects

S. boulardii is generally regarded as safe, however, an increased risk of non-infectious adverse effects (e.g., biliary tract stenoses, fistulas, lienalis-steal syndrome, abdominal hemorrhage, and acute renal failure) has been found in specific groups (e.g., immunocompromised patients, transplant patients or patients with pancreatitis). Rare cases of fungemia associated with S. boulardii have also been reported. (6)(7)(10)



  • S. boulardii is not absorbed, but concentrations stabilize within three days of oral ingestion. (6)(7)


  • Survives in the intestinal tract to reach the colon, its most common target. (6)


  • S. boulardii is not metabolized but rather dies within the competitive environment of the gastrointestinal tract and is excreted. Levels found excreted in the stool can be 100-1000 times smaller than the ingested dose. (6)


  • With a half-life of six hours, S. boulardii populations may clear after three to five days after discontinuation in the feces. (6)(7)