Thursday 03 December 2009, 12:00AM
PEARLS 131, June 2008, written by Brian R
McAvoy
(First published in New Zealand Doctor, 25 February 2009)
Clinical question
How effective are cranberry products in preventing urinary tract
infections (UTIs) in susceptible populations?
Bottom line
There was some evidence that cranberries (juice or capsules) may
decrease the number of symptomatic UTIs over a 12-month period,
particularly for women with recurrent UTIs (NNT*7). The evidence
for elderly men and women was less clear, and there was evidence
cranberry products were not effective in people who needed either
intermittent or indwelling catheters. *NNT = number needed to treat
to benefit 1 individual.
Caveat
Many people in the trials stopped drinking the juice, suggesting
it may not be a popular intervention. It is not clear how long
cranberry juice needs to be taken to be effective or what the
required dose might be.
Context
No definite mechanism of action has been established for
cranberries in the prevention or treatment of UTI. However, the
main suggestion is cranberries prevent bacteria, particularly
Escherichia coli, from adhering to uroepithelial cells lining the
bladder. Without adhesion, E. coli cannot infect the mucosal
surface of the urinary tract.
Cochrane Systematic Review
Jepson RG and Craig JC. Cranberries for preventing urinary tract
infections. Cochrane Reviews 2008, Issue 1. Article No. CD001321.
DOI: 10.1002/14651858.CD001321.pub4. This review contains 10 trials
involving 1049 participants.