WebMD Medical News
Louise Chang, MD
Oct. 16, 2012 -- Drinking cranberry juice or taking cranberry pills may do little to prevent urinary tract infection (UTI), according to a new review of the latest research.
The review of 24 studies on cranberries and UTI shows that cranberry juice and cranberry pills are unlikely to prevent the common and often painful condition.
Previous studies suggested cranberries may curb UTIs. The new review shows that any benefit from cranberries in preventing UTIs is likely to be small and only among women with recurrent UTIs.
“There might be a slight effect with the juice, but it depends on whether someone is prepared to drink cranberry juice twice a day for months on end to perhaps prevent one UTI,” says researcher Ruth Jepson, PhD, of Scotland's University of Stirling.
Urinary tract infections are one of the most common reasons people, especially women, seek medical treatment. The infection is usually caused by bacteria that enters the bladder or kidneys from the urethra, the tube that carries urine from your bladder.
Symptoms of UTI include pain or burning during urination, lower abdominal pain in the bladder area, urgent and/or frequent need to urinate, and bloody or cloudy urine.
Treatment and prevention of UTI often consists of taking antibiotics, but the bacteria can grow resistant to these drugs.
Cranberries have been a common folk and alternative remedy for UTI for decades.
Recent studies have had mixed results.
Cranberries have been widely studied for preventing urinary tract infections because they contain substances called proanthocyanidins that may prevent bacteria from sticking on the wall of the bladder, says Amy Howell, PhD, of Rutgers University’s Marucci Center for Blueberry Cranberry Research.
The new review, published in the Cochrane Database of Systematic Reviews, updates a 2008 review that concluded that cranberries may offer a small benefit in preventing UTIs in women.
Since then, another 14 studies on cranberry juice and pills have been published and added to their analysis.
Overall, the 24 studies involved 4,473 people and compared cranberry products to a placebo, no treatment, or alternative treatment in preventing urinary tract infection.
The results showed a 14% lower risk of UTI in people taking a cranberry product compared with a placebo or no treatment in people at risk for recurrent urinary tract infections. But researchers say this effect was not significant and could have been due to chance.
Many people in the studies dropped out and stopped drinking the juice, which suggests that it may not work as a long-term preventive therapy.
“It’s unlikely to be effective because it’s very difficult for people to drink cranberry juice twice a day,” Jepson says. “It’s quite a commitment.”
The study also showed cranberry pills or capsules were similarly ineffective at preventing UTIs.
Although this latest review showed cranberries were not effective in preventing urinary tract infections, experts say the debate is far from over.
“This debate will continue as it already has for many years,” says Suzanne Geerlings, MD, PhD, of the Academic Medical Center in Amsterdam, Netherlands.
Geerlings conducted a 2011 study, included in the review, that showed cranberry pills reduced the number of UTIs per year among women with recurrent UTIs compared with a placebo. But the cranberry pills did not work as well as low-dose antibiotics in preventing UTIs.
Geerlings says if someone is taking cranberry products and they are working for them to prevent UTI, they should keep doing it.
“One major advantage of cranberry pills is that they don’t lead to resistance of bacteria,” Geerlings tells WebMD.
Meanwhile, more studies are needed to look at the correct cranberry dosage needed to produce the best results.
“We don’t know the exact dose, that is one of the problems,” says Geerlings.
Jepson says many of the studies in the review did not say how much of the active ingredient was in the tablets studied.
Researchers say it may be a matter of finding the right dosage and method of extracting the active ingredients in cranberries to best prevent urinary tract infections.
Future studies should test the cranberry products for effectiveness and the correct dosage first, Howell says.
SOURCES:Jepson, R. Cochrane Database of Systematic Reviews, Oct. 17, 2012.News release, The Cochrane Library.Ruth Jepson, PhD, codirector, Center for Public and Population Health Research, University of Stirling, Stirling, Scotland.Suzanne E. Geerlings, MD, PhD, Academic Medical Center, Amsterdam, Netherlands. Amy Howell, PhD, associate research scientist, Rutgers. University’s Marucci Center for Blueberry Cranberry Research.WebMD Medical Reference: “Understanding Urinary Tract Infections -- Symptoms.” WebMD Medical News: “Cranberries Combat Urinary Tract Infections.”
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