Issue 145 Item 14 Does Cranberry Juice Prevent or Treat Urinary Tract Infection?

Cranberry juice is best suited for secondary prevention of recurrent UTI. Cranberry juice (200 mL daily to 250 mL 3 times daily) or cranberry concentrate tablets (at least 1:30 parts concentrated juice twice daily) reduce recurrent, symptomatic urinary tract infection (UTI) in women by 12% to 20% (absolute risk reduction [ARR]) compared with placebo (number needed to treat [NNT]=58). There is no conclusive evidence that cranberry juice effectively treats UTI. J Fam Pract 2003 Feb;52(2):154-5

Cranberry juice does not inhibit bacterial growth and will not sterilize the urinary tract. Also, cranberry juice does not prevent or treat UTI by changing the pH of the urine. Rather, the suspected mechanism of action is that proanthocyanidins contained in cranberry juice prevent bacterial adherence to uroepithelial cells, thus reducing the development of UTI.5 Cranberry juice has been shown to reduce uroepithelial cell adherence by bacteria resistant to trimethoprim-sulfamethoxazole.6

The protective value of cranberry juice against UTI bacteria is supported by a significant body of data from in vitro studies. The published studies examining the clinical use of cranberry juice for UTI prevention suffer from a number of flaws, including small sample size, poor design, lack of randomization, lack of placebo control, heterogeneous endpoints, and a focus on the geriatric population. Even the best of these studies suffers from a major defect: failure to use commonly available cranberry juice cocktail as the experimental intervention.

Despite these flaws, the weight of the clinical evidence suggests that cranberry juice is an effective intervention for the prevention of UTIs—especially in high-risk populations. Unfortunately, cranberry juice is expensive and its taste is displeasing to some, thus limiting its usefulness. Cranberry capsules/ tablets offer a reasonable alternative, but their composition varies greatly by manufacturer, and patient compliance may be poor.

The decision to use cranberry juice should be left to the patient and her clinician. Given the evidence, cranberry juice is best suited for secondary prevention of recurrent UTI. Patients with recurrent UTI who are being considered for antibiotic prophylaxis and are willing to drink the juice are ideal candidates. Although the studies have yet to establish an ideal dose, 3 glasses a day should be sufficient.
Brett Robbins, MD, and Steven Bondi, Internal Medicine Pediatrics Residency
University of Rochester, NY. References Cochrane Database Syst Rev 2001: CD001321. BMJ 2001; 322:1571–3. Can J Urol 2002; 9:1558–62. Can J Urol 1995; 2:98–102. Urology 2001; 57:407–13. . JAMA 2002; 287:3082–3.