Harvard Women's Health Watch

In Brief: Research backs cranberries for preventing urinary tract infections in women

In Brief

Research backs cranberries for preventing urinary tract infections in women

In what may be the biggest boost for cranberries since Thanksgiving, researchers with the highly respected Cochrane Collaboration — experts who identify and evaluate studies of health care interventions — say that scientific evidence supports daily consumption of cranberry products to reduce the likelihood of urinary tract infections (UTIs). The preventive effect is strongest in women with a history of recurrent UTIs — that is, three or more a year. Results were published in the Jan. 23, 2008, issue of the Cochrane Database of Systematic Reviews.

Cranberry juice has been used for years to treat and prevent UTIs, which are roughly 50 times more common in women than in men, according to background material accompanying the Cochrane review. UTIs can affect any part of the urinary tract but occur most often in the bladder (cystitis), producing symptoms of frequent, urgent, or painful urination, and sometimes abdominal pain or blood in the urine. Most UTIs are caused by Escherichia coli, or E. coli, which can travel from the anus to the urethra during activities such as using the toilet or having sexual intercourse. Women are more vulnerable to UTIs than men are, because a woman's urethra is close to the vagina and anus and shorter than a man's, allowing bacteria easier access to the bladder. Antibiotics are very effective in preventing and treating these infections, but many women don't like to take them because they can cause diarrhea, nausea, and yeast infections of the vagina or mouth.

The research

The Cochrane reviewers searched medical databases and clinical trial registries and consulted cranberry industry sources to find studies that lasted at least one month and compared cranberry juice, capsules, or tablets with a placebo or water for the prevention of UTIs in a variety of populations. They identified 10 studies — involving a total of 1,049 participants — that met their inclusion criteria.

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