Does Cranberry Juice Prevent Recurrent Urinary Tract Infection?

Does Cranberry Juice Prevent Recurrent Urinary Tract Infection?

In a double-blind, placebo-controlled trial among women with recent UTIs, twice-daily cranberry juice did not decrease the incidence of recurrence.

After an initial urinary tract infection (UTI), 24% of otherwise healthy women aged 18 to 39 experience a recurrence within 6 months, and 5% of women have multiple recurrences within 1 year. Cranberry juice is a well-known folk remedy for preventing UTI, and in vitro experiments have suggested that cranberries decrease the adherence of Escherichia coli to the uroepithelium. However, the effectiveness of cranberry juice in preventing UTI recurrence has not been established in randomized, controlled trials.

To examine the issue, researchers performed a prospective, double-blind trial among women aged 18 to 40 who presented to the University of Michigan Health Service between August 2005 and October 2007 with acute UTIs. The 319 participants were randomized to receive 8 ounces twice daily of placebo juice or of low-calorie cranberry juice cocktail standardized for its concentration of proanthocyanidin (its presumed active ingredient). A clean-catch urine sample was collected for culture at baseline, 3 months, and 6 months, and at visits associated with UTI episodes.

During the 6-month study period, 54 culture-confirmed recurrent UTI episodes were observed. The recurrence rate — 16.9% overall — was 19.3% in the cranberry juice group and 14.6% in the placebo group (P=0.21).

Comment: These findings fail to demonstrate a decreased risk for recurrent UTI in those consuming cranberry juice. However, as the authors point out, something other than proanthocyanidin might be the active factor, and the placebo might inadvertently have contained this ingredient. Therefore, this study is probably not the last word on cranberry juice and UTI prevention.

— Neil M. Ampel, MD

Published in Journal Watch Infectious Diseases January 19, 2011