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Saccharomyces boulardii is a probiotic, or a beneficial, yeast strain. We think of it as a supplement, as it’s the only commercially available probiotic yeast, but it also is part of our naturally occurring flora as well.

Most probiotics sold as supplements focus on repopulating the good bacteria. What does saccharomyces contribute that commensal bacterial strains do not?

Saccharomyces: For Acute GI Infections and Prevention

S. boulardii is perhaps most often thought of for acute gastroenteritis with diarrhea, regardless of the causative organism. Indeed, it has been shown to be beneficial for many such organisms.

S. boulardii is beneficial for clostridia difficile, or C. diff infections. It inhibits the growth of the organism itself, while increasing the body’s antibody production against C. diff toxins. It’s been shown to be beneficial for recurrent C. diff as well.

S. boulardii also inhibits secretion of the toxin produced by cholera, blocks activity of hemorrhagic E. coli, and prevents adhesion of the parasite Entamoeba histolytica.

Of course, many of these infections are also treated with antibiotics, which in and of themselves can disrupt good gut flora and induce imbalance and diarrhea. Yeast is resistant to antibiotics—one reason why yeast infections tend to follow antibiotic treatment—so s. boulardii survives antibiotic treatment well. It also helps the normal microbiome to reestablish itself much faster than it might without treatment, helping to prevent antibiotic-induced diarrhea.

Saccharomyces: For Chronic Inflammatory GI Conditions

In cases of chronic GI distress without acute infection, saccharomyces can also be beneficial. This study shows that it helps modulate the inflammatory response in cases of Irritable Bowel Disease (IBD).

This may be in part due to the fact that it helps the cells of the gut (the enterocytes) to mature, in addition to aiding in the balance of the microbiome.

Saccharomyces for Dysbiosis

In this study, those with chronic diarrhea secondary to dysbiosis, or imbalance in the gut flora, achieved resolution of symptoms and restoration of microbial homeostasis with s. boulardii. At the same time, the microbial balance in those with healthy guts remained unaffected.

This may in part be due to the fact that s. boulardii helped to increase short chain fatty acid (SCFA) production, and particularly butyrate. Short chain fatty acids are the food for the cells in the colon.

Saccharomyces for Recurrent Yeast Infections

It might seem counterintuitive to treat a yeast infection with another yeast—but s. boulardii is in fact effective against candida overgrowth, in much the same way that good bacteria can aid in the fight against imbalanced or pathogenic bacteria.

This study shows that s. boulardii interferes with candida’s ability to produce biofilms, which, in addition to its tendency to aid in general microbial balance, may be part of how it works.

Saccharomyces for Gut Immune Modulation

The first line of the gut’s own immune function comes from secretory immunoglobulin A (sIgA). When this is low, the gut’s defenses against pathogenic invaders are down. S. boulardii increases sIgA production.

The Upshot

S. boulardii is perhaps unnecessary for those with no gut symptoms to speak of. But for those struggling with acute or recurrent dysbiosis, GI inflammation, low sIgA, it helps to modulate the immune response and support gut health.