May 2007

A Unique Probiotic Yeast
Saccharomyces boulardii is a unique non-pathogenic yeast that has been safely used worldwide as a probiotic for more than half a century. It does not colonize the intestinal tract and is used as needed to support intestinal health. Classified as a variant of Saccharomyces cerevesiae, S. boulardii is genetically and metabolically different from other S. cerevisiae strains. It is not related to the Candida yeast group. Highly resistant to heat and acid, S. boulardii provides the intestines with unparalleled support against a broad array of pathogens that include bacteria, yeast, and protozoans.

Support Against Clostridium difficile
S. boulardii is best known for its activities against Clostridium difficile. It secretes a protease that inhibits Clostridium difficile enterotoxin A and cytotoxin B. This protease lyses enterotoxin A and inhibits binding of both toxins by disrupting their intestinal receptors. Enterotoxin A-mediated intestinal water and electrolyte secretion is diminished and intestinal permeability reduced. S. boulardii stimulates the gut’s immune response against enterotoxin A and inhibits C. difficile adherence to intestinal mucosal cells.

Support Against Gram-negative Pathogens
S. boulardii is the active ingredient in herbal teas traditionally used in Asia for the treatment of cholera and other dysenteries. Cholera is caused by Vibrio cholerae which produces a toxin that stimulates chloride secretion by intestinal cells causing voluminous watery diarrhea. S. boulardii secretes a small protein that significantly decreases the toxin’s effect on metabolic signaling and reduces chloride secretion to normal levels. Enteropathogenic Escherichia coli (EPEC) is the predominant bacterial cause of infantile gastroenteritis. Enterohemorrhagic E. coli (EHEC) in contaminated food is implicated in hemorrhagic gastroenteritis and renal failure. S. boulardii significantly inhibits the EPEC toxin that causes acute diarrhea. S. boulardii restores intestinal barrier function during E. coli infections, inhibits EHEC-induced cell death, decreases tumor necrosis factor-a production, and significantly reduces the number of E. coli internalized by enterocytes. In animal studies, S. boulardii inhibits the inflammatory pathways activated by Listeria monocytogenes and Salmonella typhimurium. It reduces the number and severity of intestinal lesions caused by S. typhimurium and decreases the mortality associated with Shigella flexneri infection.

Support Against Candida
S. boulardii is commonly used to support intestinal health in people with Candida overgrowth. Animal studies have shown that S. boulardii antagonizes C. albicans, C. krusei, and C. pseudotropicalis, but is ineffective against C. tropicalis. S. boulardii effectively inhibits and eliminates Candida overgrowth by susceptible species. S. boulardii has been shown to reduce the translocation of C. albicans in immunosuppressed mice from the gastrointestinal tract to other organs such as the spleen and liver. S. cerevisiae species have developed complex yeast killer systems involving exotoxins. As a variant S. cerevisiae species, it is highly likely that S. boulardii possesses antifungal exotoxins that kill and inhibit Candida species. The exact nature of S. boulardii’s anti-Candida properties have yet to be elucidated.

Support Against Amoebic Parasites
Intestinal amoebiasis is caused by the amoeba Entamoeba histolytica, a protozoan found worldwide. E. histolytica can exist in the intestines as a parasite giving rise to no symptoms or it can invade the intestinal lining causing dysentery and spread to the liver and other organs causing abscesses. S. boulardii together with antibiotics (metronidazole and iodoquinol) has been shown to significantly shorten the duration of diarrhea and accelerate the clearance of amoebic cysts from the stool compared to antibiotics alone. The antiparasitic properties of S. boulardii have only recently received attention.