Cranberry juice may not head off UTIs

Cranberry juice may work no better than placebo to prevent recurrent urinary tract infections (UTIs), a new double-blind, placebo-controlled trial suggests.

The University of Michigan study followed 319 college women who had tested positive for acute UTI. They were assigned to drink 8 oz of cranberry juice or placebo for 6 months or until their UTI recurred, whichever came first. Participants who drank cranberry juice had a recurrence rate of almost 20% compared with 14% of placebo drinkers. The study will be published online in Clinical Infectious Diseases (January 1, 2011).

“We assumed that we would observe a 30% recurrence among the placebo group,” said lead author Betsy Foxman, PhD, of the University of Michigan School of Public Health, Ann Arbor. “It is possible that the placebo juice inadvertently contained the active ingredients that reduce urinary tract infection risk, since both juices contained vitamin C.”

Another possible explanation, she added, is that “the study protocol kept participants better hydrated, leading them to urinated more frequently, therefore decreasing bacterial growth and reducing urinary tract infection symptoms.”

Cranberry juice has been recommended to help prevent UTIs based on observational studies and a few small clinical trials. The highest incidence of UTIs occurs among women between 18 and 24 years of age.