Cranberries can prevent recurrent urinary tract infections in women

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.
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.
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.
Review CD#: 
June, 2008
Authored by: 
Brian R McAvoy