It's a fact: cranberry juice reduces the risk for women of getting urinary tract infections. How? Researchers believe that the combination of fructose and substances called proanthocyanidins found in cranberries prevents bacteria (particularly E. coli) from sticking to the uroepithelial cells that line the bladder walls and infecting the surface of the urinary tract. "The cranberry juice phytochemicals bind to the bacteria, and then they're just excreted," says Jeffrey Blumberg, director of the antioxidants research laboratory at the USDA human nutrition research center on aging at Tufts University.
But, so far, there is no proof that cranberry juice can treat urinary tract infections. Though proanthocyanidins and fructose can prevent the bacteria from sticking to the walls of the bladder, there is no evidence that once the bacteria are stuck, the active components of cranberries can remove them, says Ruth Jepson, senior research fellow at the University of Stirling in Scotland, who has studied cranberry juice and UTIs.
Not everyone wants to, or needs to, drink cranberry juice. Women who have never had a UTI shouldn't feel compelled to down it. "To take it because you're hoping to prevent a UTI and you never really had one, it wouldn't be as critical as someone who chronically ends up with urinary tract infections," says Susan Moores, a registered dietitian in St. Paul, Minn., and a spokeswoman for the American Dietetic Association. "[But] it certainly wouldn't hurt." The big benefit: "If it is effective, that means less use of antibiotics, which is good, and then less risk of creating bacteria resistant to antibiotics," says Lona Sandon, a registered dietitian at the University of Texas Southwestern. "In the long run it comes out better for your health and your health dollar." (UTIs are typically treated with oral antibiotics.)
It's unclear exactly how much juice women prone to UTIs should drink. "This is essentially a drink, not a medicine, so it hasn't been subjected to a lot of dose-response studies," says Jepson. The best estimate: at least 10 ounces, the amount consumed by women in a study conducted by the Journal of the American Medical Association. Calorie-counting women may want to choose sugar-free juice. (Cranberry juice is often sweetened, since it's tart otherwise.) Linda Van Horn, professor of preventive medicine at Northwestern University, keeps the light version in her house. "It includes all the benefits of the cranberry without having tons of sugar dumped into it," she says. Studies have not been consistent regarding what type of cranberry juice women drink, but several used a juice with a 30 percent concentration of cranberries.
What should cranberry juice haters do? Try other UTI-preventing strategies, such as wiping from front to back after urination, urinating after intercourse or simply drinking a lot of fluids. That can help wash bacteria out of the body. Or try consuming cranberries in another form (though keep in mind that it will take a lot of cranberry bread to get the same dose). Sandon recommends throwing some dried cranberries on a salad, or in oatmeal instead of raisins. No one has specifically studied cranberry bread, cranberry sauce or dried cranberries, but researchers say they would probably work just as well if the dose were the same.
Cranberry juice, high in antioxidants, may also help prevent heart disease.