Saccharomyces boulardii is a probiotic yeast that has been studied extensively for its effects on gastrointestinal health, including the stomach. There is scientific validation for its use in managing and preventing various gastrointestinal disturbances. Clinical trials and systematic reviews have shown that S. boulardii can help reduce the duration and severity of acute infectious diarrhea, particularly in children and adults, and can prevent antibiotic-associated diarrhea and Clostridioides difficile infections. It exerts its benefits through several mechanisms, including modulation of the gut microbiota, enhancement of the intestinal barrier function, and inhibition of pathogenic bacteria and their toxins. While most research focuses on the intestines, there is also evidence that S. boulardii can help protect the gastric mucosa, reduce inflammation, and may support the stomach during gastrointestinal infections or after antibiotic use.

Multiple randomized controlled trials and meta-analyses support these outcomes, and guidelines from some gastroenterological societies acknowledge its utility in certain situations. However, its application is best established for intestinal, rather than purely gastric, conditions. In summary, the use of Saccharomyces boulardii to support the stomach and upper gastrointestinal tract is supported by a substantial body of scientific evidence, particularly in the context of infectious or antibiotic-associated disruptions.