Urinary Tract Infections Not Prevented by Cranberry Juice

Laurie Barclay, MD

October 17, 2012

Because the benefit for prevention is small, cranberry juice cannot currently be recommended to prevent urinary tract infections (UTIs), according to a systematic review published online October 16 in the Cochrane Review. This is the third update of a previous Cochrane review on the same topic first published in 1998 and then updated in 2004 and 2008.

"Now that we've updated our review with more studies, the results suggest that cranberry juice is even less effective at preventing UTIs than was shown in the last update," lead author Ruth G. Jepson, PhD, from the Department of Nursing and Midwifery, University of Stirling in the United Kingdom, said in a news release.

Because the use of cranberries to prevent and treat UTIs has been widespread for several decades, the goal of this review was to determine the efficacy of cranberry products in preventing UTIs in populations at risk.

The investigators searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and online sources through July 2012, as well as bibliographies of retrieved studies and reviews. In addition, they consulted with companies marketing cranberry products.

Inclusion criteria were randomized controlled trials (RCTs) or quasi-RCTs evaluating cranberry products to prevent UTIs. Two reviewers independently examined and synthesized data regarding methods, patients, interventions and outcomes including the incidence of symptomatic UTIs, positive cultures, adverse effects, and treatment compliance.

When meta-analysis and calculation of risk ratios (RR) were not feasible, the reviewers synthesized the data in narrative form. The Cochrane risk of bias assessment tool allowed evaluation of methodological quality.

Of 24 included studies enrolling a total of 4473 participants, 10 studies were included in the 2008 update; therefore, 14 studies have been added for the current analysis. Six of the 24 studies were crossover studies, 11 were 2-arm parallel group studies, 5 were 3-arm parallel group studies, and 2 studies had a factorial design. The studies compared cranberry products with placebo, no treatment, water, methenamine hippurate, antibiotics, or lactobacillus.

Compared with placebo, water, or no treatment, cranberry products were not associated with significant reductions in the occurrence of symptomatic UTI overall (RR, 0.86; 95% confidence interval [CI], 0.71 - 1.04). Cranberry products also had no apparent protective effect in any subgroups, including women with recurrent UTIs, older people, pregnant women, children with recurrent UTI, patients with cancer, and patients with neuropathic bladder or spinal injury.

Compared with antibiotics, cranberry was not significantly different in efficacy for women or for children, based on 3 small studies. Gastrointestinal adverse effects were similar for cranberry products and for placebo or no treatment (RR, 0.83; 95% CI, 0.31 - 2.27).

Compliance was low and dropout rate high in many studies, which may have resulted from poor acceptability of cranberry juice and of other cranberry products to a lesser extent.

Other limitations of this study include a lack of reporting in most studies of cranberry tablets and capsules of how much active ingredient the product contained. There was moderate heterogeneity among studies overall.

"We can't see a particular need for more studies of the effect of cranberry juice, as the majority of existing studies indicate that the benefit is small at best, and the studies have high drop-out rates," Dr. Jepson said in the news release. "More studies of other cranberry products such as tablets and capsules may be justified, but only for women with recurrent UTIs, and only if these products contain the recommended amount of active ingredient."

The United Kingdom National Health Services, National Institute for Health Research provided funding for the 2012 update of the review. Dr. Jepson received grant funding from Nuffield Trust. The authors have disclosed no relevant financial relationships.

Cochrane Database Syst Rev. Published online October 16, 2012. Abstract