It's true. A glass of cranberry juice a day may keep a urinary tract infection (UTI) away.
Cranberry juice, an old-time folk remedy, has held up under scientific scrutiny in recent years. One of the cornerstone studies was a well-controlled trial performed on elderly women at Harvard Medical School that was published in The Journal of the American Medical Association (JAMA).
The study found that women who drank cranberry juice were 58 percent less likely to develop a UTI than those who drank a "placebo." That is, another reddish drink that tasted like cranberry juice and contained vitamin C. If they already had an infection, they were 27 percent less likely to have their infections continue if they drank cranberry juice.
The findings have come as good news to women, who are more prone to UTIs than men. Nearly half of all American women, at some point, experience cystitis, a bladder infection, which make up nearly 95 percent of all UTIs.
"Do I believe in cranberry juice? Yes, I believe in it," says Susan Kolata, M.D., an Arizona urologist and president of the Society of Women in Urology.
What's in the cranberry?
Doctors have always recommended patients with UTIs drink plenty of fluids, since fluids help flush bacteria from the urinary tract. But that never explained why cranberry juice had such an edge over water or orange juice.
What cranberry juice had, it turns out, that the others didn't was an "anti-adherence factor," Kolata says. Studies found cranberries (and blueberries as well) contain a compound that makes it tough for the bacteria to adhere to the bladder wall. The bacteria that cause 90 percent of all UTIs are E.coli.
The compound is found only in cranberry and blueberry juices and not in others.
Just how much cranberry juice is most beneficial isn't clear. The women in the JAMA study who got cranberry juice were given a 10-ounce glass - a few ounces less than a can of soda - every day.
"We don't know if more is better," Kolata says.
What is clear from the studies, though, is that cranberry juice is best used as a preventive measure. When an infection has already taken hold, Kolata says, antibiotics are the cure, although drinking the cranberry juice may help speed recovery, as the JAMA study showed.
"If someone gets recurrent infections, I do recommend cranberry juice," Kolata says.
If you don't like the taste of cranberry juice, then you can skip the juice and try cranberry tablets, which you can buy in a health food store. With the tablets, you can also avoid the extra sugar that is found in the juice. This is important for people with diabetes.
Also, people with a history of kidney stones should not drink large amounts of cranberry juice.
Are there other benefits of the berries?
Meanwhile, researchers continue to explore the medicinal properties of the cranberry as well as the wild blueberry, which is a cousin to the cranberry.
Researchers at The University of Western Ontario have completed a study that suggests cranberry products could have cancer-fighting properties. The study, funded by Ocean Spray Cranberries, Inc., documented regular consumption of cranberry products may inhibit the development of breast cancer tumors in animals.
Cranberries are a rich source of flavonoids, a variety of compounds produced by plants that have been investigated for their anti-cancer activity.
Researchers at the University of Illinois have been studying the health effects of wild blueberries and cranberries since 1994. In preliminary studies, they, too, found blueberry flavonoids that inhibit enzymes involved in the initial stages of cancer development.
In yet another study, researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRC) at Tufts University found rats got smarter when fed diets with blueberry extract. The rats had better cognitive and motor function than rats fed other diets.
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External Source
 | National Kidney and Urologic Disease Information Clearinghouse (NKUDIC)
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This article was reviewed and updated June 2007.
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