Cranberries of Little Help in Preventing UTI (CME/CE)

Authors: MedPage Today

By Cole Petrochko, Staff Writer, MedPage Today
Published: October 16, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

Cranberry products were no more effective at preventing urinary tract infections (UTIs) than a range of other treatments in most populations, a systematic review found.

An updated Cochrane Library review of studies comparing the use of various cranberry products against a range of placebo, drug, and nondrug treatments for preventing symptomatic UTIs showed cranberry products did not outperform placebo overall (RR 0.86, 95% CI 0.71 to 1.04) and in most subpopulations.

However, cranberry products -- such as tablets or capsules -- were as effective as antibiotics at preventing recurrent UTIs in women (RR 1.31, 95% CI 0.85 to 2.02) and children (RR 0.69, 95% CI 0.32 to 1.51), according to Ruth Jepson, PhD, of the University of Stirling in England, and colleagues.

"Prior to the current update, it appeared there was some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12-month period, particularly for women with recurrent UTIs," they noted, but the "addition of 14 further studies suggests that cranberry juice is less effective than previously indicated."

Prior research has suggested that cranberries prevent adhesion of bacteria to uroepithelial cells in the bladder, although the researchers noted that there is no definitive mechanism of action established for that protective effect.

The analysis included a combined 4,473 patients from a total of 24 studies -- including 14 new studies in the most recent update -- who had a history of recurrent lower UTIs, were older, needed intermittent catheterization, were pregnant, had an in-dwelling catheter, had an abnormality of the urinary tract, or were a child with a first or subsequent UTI.

Interventions lasted at least 1 month, included cranberry juice, cranberry juice cocktail, capsules, tablets, extract, and syrup, and were measured against placebo, water, methenamine hippurate, antibiotics, lactobacillus, or no treatment. Some studies also measured one cranberry product against another.

Outcomes included number of UTIs, adherence to treatment, and adverse events.

Cranberry products failed to significantly prevent UTI overall (RR 0.86, 95% CI 0.71 to 1.04), as well as in most at-risk populations studied including:

  • Women with a recurrent UTI: RR 0.74, 95% CI 0.42 to 1.31
  • Older patients: RR 0.75, 95% CI 0.39 to 1.44
  • Adults and children needing catheterization: RR 0.95, 95% CI 0.75 to 1.20
  • Pregnant women: RR 1.04, 95% CI 0.93 to 1.16
  • Children with a susceptibility to UTIs: RR 0.48, 95% CI 0.19 to 1.22
  • Patients undergoing radiation treatment: RR 1.15, 95% CI 0.75 to 1.77

Among women with a recurrent UTI and after adjusting for one study with significant heterogeneity of results, cranberry was significantly associated with prevention of UTI (RR 0.58, 95% CI 0.39 to 0.86).

Several studies also compared cranberry against other treatments for preventing UTI. Compared with probiotic treatment, cranberry was significantly associated with prophylaxis (RR 0.42, 95% CI 0.24 to 0.74).

However, cranberry products did not perform significantly better against:

  • Antibiotics: RR 1.31, 95% CI 0.85 to 2.02 (in adults) RR 0.69, 95% CI 0.32 to 1.51 (in children)
  • Low or high cranberry dose: RR 1.12, 95% CI 0.75 to 1.68
  • Methenamine hippurate: RR 1.02, 95% CI 0.79 to 1.31

The researchers noted that the studies had a large dropout rate -- from 0% to 55% -- and that "the benefit for preventing UTI is small," as well as a lack of standardized quantification of active ingredient in alternative doses of cranberry. As a result, they concluded that the products could not be recommended for UTI prevention.

The authors noted that the research was limited by the small sample sizes and small power of some studies.

The study was funded by the U.K. NHS NIHR.

No conflicts of interest were reported.

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