A probiotic containing the non-pathogenic yeast Saccharomyces boulardii with antidiarrheal and potential anti-inflammatory, antimicrobial and immunomodulating activities. As a dietary supplement, S. boulardii may improve digestion and help maintain adequate colonization of the gastrointestinal (GI) tract by modulating the composition of the normal intestinal microflora. During colonization of the GI tract, S. boulardii forms a protective barrier that helps maintain the integrity of the epithelial barrier. This prevents attachment of pathogens to the intestinal mucosa. In addition, this probiotic secretes a protease that binds to and degrades toxins A and B produced by Clostridium difficile, thereby preventing their harmful effects. Dietary supplementation with this microorganism may reduce the secretion of proinflammatory cytokines and may potentiate natural and acquired immunity.