Cranberry-containing products for prevention of urinary tract infections in susceptible populations: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Urinary tract infection (UTI) is one of the most commonly acquired bacterial infections. Cranberry-containing products have long been used as a folk remedy to prevent UTIs. The aims of this study were to evaluate cranberry-containing products for the prevention of UTI and to examine the factors influencing their effectiveness. METHODS: MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were systemically searched from inception to November 2011 for randomized controlled trials that compared prevention of UTIs in users of cranberry-containing products vs placebo or nonplacebo controls. There were no restrictions for language, population, or publication year. RESULTS: Thirteen trials, including 1616 subjects, were identified for qualitative synthesis from 414 potentially relevant references; 10 of these trials, including a total of 1494 subjects, were further analyzed in quantitative synthesis. The random-effects pooled risk ratio (RR) for cranberry users vs nonusers was 0.62 (95% CI, 0.49-0.80), with a moderate degree of heterogeneity (I(2) = 43%) after the exclusion of 1 outlier study. On subgroup analysis, cranberry-containing products seemed to be more effective in several subgroups, including women with recurrent UTIs (RR, 0.53; 95% CI, 0.33-0.83) (I(2) = 0%), female populations (RR, 0.49; 95% CI, 0.34-0.73) (I(2) = 34%), children (RR, 0.33; 95% CI, 0.16-0.69) (I(2) = 0%), cranberry juice drinkers (RR, 0.47; 95% CI, 0.30-0.72) (I(2) = 2%), and subjects using cranberry-containing products more than twice daily (RR, 0.58; 95% CI, 0.40-0.84) (I(2) = 18%). CONCLUSIONS: Our findings indicate that cranberry-containing products are associated with protective effect against UTIs. However, this result should be interpreted in the context of substantial heterogeneity across trials.