Saccharomyces boulardii is a probiotic yeast that has been extensively studied for its role in supporting gut health during and after antibiotic treatment. Its primary use is not as an alternative to antibiotics—since it does not kill pathogenic bacteria—but as a supportive measure to help prevent or reduce antibiotic-associated side effects, particularly diarrhea (including Clostridioides difficile-associated diarrhea).

Multiple randomized controlled trials and meta-analyses have shown that S. boulardii supplementation can significantly reduce the incidence and duration of antibiotic-associated diarrhea in both adults and children. The proposed mechanisms include restoration of the gut microbiota balance, inhibition of pathogenic bacteria, enhancement of gut barrier function, and modulation of the immune response.

Clinical guidelines (such as those from ESPGHAN and the World Gastroenterology Organisation) acknowledge the efficacy of S. boulardii in this context. However, it is important to note that S. boulardii is not a substitute for antibiotics when antibiotics are clinically indicated. Rather, it is used adjunctively to minimize the disruption antibiotics can cause to the gut microbiome and to reduce the risk of complications like C. difficile infection. Safety concerns are minimal in healthy individuals but caution is advised in immunocompromised patients.

In summary, the use of S. boulardii as a supportive agent during antibiotic therapy is supported by robust scientific evidence, but it should not be considered an alternative to antibiotics for treating infections.