While it has long been believed that cranberry juice can help prevent all-too-common bladder and kidney infections, a new study says its unlikely to do any good.
A new review published Wednesday in The Cochrane Library analyzed recent evidence and came to the conclusion that any benefit of drinking the juice is likely to be extremely small and only for women with recurrent urinary tract infections (UTI).
While it isn't exactly clear why cranberry juice has been thought to be beneficial, some scientists suggest that certain sugars and flavanol compounds in cranberries prevent bacteria from sticking to cells lining the walls of the urinary tract.
Researchers in the UK gathered together evidence from 24 studies that involved nearly 4,500 subjects, with the test groups given cranberry juice, tablets, or capsules. In the review, researchers focused on cranberry juice and products as a prevention method for subjects with urinary or kidney infections, not as a treatment for an acute infection.
Although in some studies there were small benefits for women suffering from recurring infections, women would have to consume two glasses of cranberry juice per day for long periods to prevent one infection.
Sticking to the daily routine is a major commitment, lead researcher Ruth Jepson of the University of Stirling in the UK told WebMD UK. "You do wonder in real life how many women would be prepared to drink that amount."
Yet past research has shown more positive results. Earlier this year a Taiwanese review of 13 studies concluded that UTIs were 38 percent rarer among people who consume cranberry products, notes WebMD UK. But Jepson adds that her study was more "robust."
She does suggest that more studies of other cranberry products such as tablets and capsules could be justified, "but only for women with recurrent UTIs, and only if these products contain the recommended amount of active ingredient," she says.