Among things all females learn early on is that you guzzle cranberry juice to prevent a urinary tract infection, which one in five women will eventually get. The reason: cranberries contain proanthocyanidins, or PACs, which can keep bacteria from sticking to the bladder and urinary tract. That's why a JAMA study published Thursday is so shocking: Leaving the "world rocked," per the New York Daily News, researchers say the idea is nothing more than an old wives' tale. After analyzing 147 older women in nursing homes—where UTIs are the most commonly diagnosed infection, per CNN—they found no variance in the number of UTIs among patients given 72 milligrams of PAC daily in cranberry capsules (the equivalent of 20 ounces of juice) and those given placebos, reports Science Alert.
There was also no difference in terms of bacteria found in urine. "Although our study was only in nursing home women, many other studies have been done in other populations, which have not shown a benefit," says lead author Manisha Juthani-Mehta. For example, a 2012 review of 24 studies on cranberry juice, which is still touted by the American Congress of Obstetricians and Gynecologists, determined it "cannot be recommended for the prevention of UTIs." Paying for cranberry capsules with "limited potential benefit" for preventing UTIs, therefore, "does not seem worthwhile," says Juthani-Mehta. Another option: "For postmenopausal women, topical estrogen in the vagina has [been] shown to decrease the risk of UTI," a scientist says. (There is science behind this old wives' tale.)