Eight randomised placebo controlled clinical trials (n=1,011) were included in the meta analysis. Two studies were of low quality and the rest scored high (3 or above). The range of follow-up was four to 48 weeks.
Probiotics were reported to significantly increase clinical improvement compared to placebo (RR 1.22, 95% CI: 1.07 to 1.4, p=0.0042). Clinical improvement was reported as 53.1% (292/550) in probiotic groups compared to 44.9% (167/372) in the placebo group.
Elimination of low quality studies from the meta analysis did not significantly influence the result. No publication bias was reported. No evidence of heterogeneity was found.