Clinical Question: Are probiotics effective in the prevention of acute diarrhea?

Setting: Various (meta-analysis)

Study Design: Meta-analysis (randomized controlled trials)

Synopsis: Probiotics are effective in the treatment of acute infectious diarrhea in adults and children. However, evidence supporting the role of probiotics in preventing acute diarrhea is less certain. The investigators searched multiple databases, including MEDLINE, the Cochrane Registry, and references of published review articles. They also contacted experts in probiotics. Only randomized, double-blind, placebo-controlled trials in English or French were included in the analysis. Three individuals evaluated articles for eligibility and quality; disagreements were resolved by consensus discussion.

A total of 34 trials, which included 4,844 patients from six months to 71 years of age, met the inclusion criteria. Overall, probiotics reduced the risk of acquiring diarrhea by 33 percent (95% confidence interval [CI], 22 to 44 percent; number needed to treat = 15; 95% CI, 11 to 22). In subgroup analyses, probiotics significantly reduced the risk of antibiotic-associated diarrhea and acute diarrhea of other types, but they did not reduce the risk of traveler’s diarrhea. Probiotics were more effective in children than in adults, and the protective effect did not vary significantly among different probiotic strains or by mode of delivery (i.e., capsules, tablets, granules, or powder). A formal analysis found no evidence of significant publication bias.

Bottom Line: Probiotics reduce the risk of antibiotic-associated diarrhea and other types of acute diarrhea, but not the risk of traveler’s diarrhea, in children and adults. The protective effect does not vary among different probiotic strains or by mode of delivery. (Level of evidence: 1a)