Cranberries for preventing urinary tract infections.

BACKGROUND: Cranberries (particularly in the form of cranberry juice) have been used widely for several decades for the prevention and treatment of urinary tract infections. The aim of this review is to assess the effectiveness of cranberries in preventing such infections.

OBJECTIVES: To assess the effectiveness of cranberry juice and other cranberry products in preventing urinary tract infections in susceptible populations.

SEARCH STRATEGY: Electronic databases and the Internet were searched using English and non English language terms; companies involved with the promotion and distribution of cranberry preparations were contacted; reference lists of review articles and relevant trials were searched.

SELECTION CRITERIA: All randomised or quasi randomised controlled trials of cranberry juice/products for the prevention of urinary tract infections in susceptible populations. Trials of men, women or children were included.

DATA COLLECTION AND ANALYSIS: Reviewers RJ and LM independently assessed and extracted information using specially designed data extraction forms. For each included trial, information was collected on methods of the trial, participants, interventions and outcomes. We were unable to perform statistical analysis due to the nature of the data available for review.

MAIN RESULTS: Four trials met the inclusion criteria (three cross-over, one parallel group). Three compared the effectiveness of cranberry juice versus placebo juice or water and one compared the effectiveness of cranberry capsules versus placebo. Two further trials were excluded. The outcomes of interest were number of urinary tract infections in each group (symptomatic and asymptomatic), side effects and adherence to therapy. Data from three out of the four trials indicated that cranberries were effective for at least one of the outcomes of interest. The quality of the four included trials was poor, however, and thus the reliability of the results must be questionable.

REVIEWER'S CONCLUSIONS: The small number of poor quality trials gives no reliable evidence of the effectiveness of cranberry juice and other cranberry products. The large number of dropouts/withdrawals from the trials indicates that cranberry juice may not be acceptable over long periods of time. Other cranberry products such as cranberry capsules may be more acceptable. On the basis of the available evidence, cranberry juice cannot be recommended for the prevention of urinary tract infections in susceptible populations. Further properly designed trials with relevant outcomes are needed.