Evidence Level
Strong
S. boulardii has one of the strongest evidence bases among all probiotics. Its unique advantage as a yeast is complete resistance to antibacterial antibiotics, making it the ideal probiotic for concurrent use during antibiotic therapy. Multiple Cochrane and systematic reviews support its use for AAD prevention (NNT=10), C. difficile recurrence prevention, and acute pediatric diarrhea. The WHO recommends it as an adjunct for acute diarrhea management. Its mechanism involves direct toxin degradation, sIgA stimulation, and anti-inflammatory signaling — not competitive exclusion like bacterial probiotics.