Salari, P., Nikfar, S., & Abdollahi, M. (2012). A meta-analysis and systematic review on the effect of probiotics in acute diarrhea. Inflammation & Allergy Drug Targets, 11(1), 3–14.

To clarify the efficacy of probiotics in children and adults

• Databases searched were PubMed, Web of Science, Scopus, and the Cochrane Database.
• Search keywords were probiotics and diarrhea.
• Studies were included in the review if they were randomized clinical trials (RCTs) and involved children.
• Studies were excluded if they were uncontrolled trials or the results did not address study goals.

• A total of 1,228 references were retrieved.
• The Jadad scale quality rating was used to evaluate the literature.

• The final review involved 20 studies with total sample of 3,867 patients. Sample sizes ranged from 69–913 patients.
• Most trials involved children. Two studies were included regarding radiation-induced diarrhea and one trial involved chemotherapy-related diarrhea. These studies were not included in the meta-analysis.

The effect size for probiotics compared to placebo in 19 trials related to duration of diarrhea was -0.67 (95% confidence interval [CI] = -0.95–0.38) in favor of probiotics. Heterogeneity was statistically significant. Findings included evaluation of duration of diarrhea, hours of fever, duration of hospitalization, duration of vomiting, and number of stools per day. Authors reviewed subsets of information for children, adults, cases of amebiasis and clostridium difficile, HIV, and radiation or chemotherapy.

Taken as a whole, authors concluded insufficient evidence exists for the efficacy of probiotics for different types of diarrhea in children or adults.

• Very few of the trials were relevant to oncology.
• Trials involved both children and adults. However, only the trials involving children were included in the meta-analysis. 
• High heterogeneity existed among the studies. 
• Variations in specific probiotics may have influenced results.
• The authors noted the need for agreement among researchers in defining measurements including what constitutes the end of diarrhea.

These findings did not provide strong support for the use of probiotics for prevention or management of diarrhea in patients receiving radiation or chemotherapy. Overall evidence in all groups was limited by a number of factors. The specific type, dosages, and timing of probiotic use varied.