Cranberry Reduces the Risk of Urinary Tract Infection Recurrence in Otherwise Healthy Women: A Systematic Review and Meta-Analysis.

Background: Cranberry ( Vaccinium spp.) has been advocated for treatment of urinary tract infection (UTI); however, its efficacy is controversial. Women have a 50% risk of UTI over their lifetime, and ∼20-30% experience a subsequent UTI recurrence. Objective: We conducted this meta-analysis to assess the effect of cranberry on the risk of UTI recurrence in otherwise healthy women. Methods: Literature published before January 2011 was obtained from 2 published systematic reviews, and we conducted updated searches in EMBASE and MEDLINE (through July 2017). We included randomized controlled trials that were conducted in generally healthy nonpregnant women aged ≥18 y with a history of UTI, compared cranberry intervention to a placebo or control, and reported the outcome as the number of participants experiencing a UTI. Two researchers conducted abstract and full-text screenings, data extractions, and risk of bias assessments independently, and discrepancies were resolved by group consensus. Meta-analyses were performed by using Stata SE software (version 13). We employed a fixed-effect model using the Mantel-Haenszel method to estimate the summary risk if the heterogeneity was low to moderate ( I 2 < 50%). Otherwise, we applied a random-effects model using the DerSimonian-Laird method. Results: We identified 7 randomized controlled trials conducted in healthy women at risk of UTI ( n = 1498 participants). Results of the meta-analysis showed that cranberry reduced the risk of UTI by 26% (pooled risk ratio: 0.74; 95% CI: 0.55, 0.98; I 2 = 54%). Risk of bias indicated that 2 studies had high loss to follow-up or selective outcome reporting. Overall, the studies were relatively small, with only 2 having >300 participants. Conclusion: These results suggest that cranberry may be effective in preventing UTI recurrence in generally healthy women; however, larger high-quality studies are needed to confirm these findings. This trial was registered at crd.york.ac.uk/prospero as CRD42015024439.