Available from Now Foods, Saccharomyces boulardii is a probiotic yeast that survives stomach acid and colonizes the intestinal tract. It promotes the health of the intestinal tract, helps to encourage a healthy gut flora balance, and supports a balanced intestinal response to normal internal and environmental stressors. Saccharomyces boulardii has also been shown to support proper gastrointestinal function during temporary disruptions to the normal balance of gut flora.