Cranberry juice not effective against urinary tract infections, study suggests

College-aged women who tested positive for having a urinary tract infection were assigned to drink eight ounces of cranberry juice or a placebo twice a day for either six months or until a recurrence of a urinary tract infection, whichever happened first. Of the participants who suffered a second urinary tract infection, the cranberry juice drinkers had a recurrence rate of almost 20 percent, while those who drank the placebo suffered only a 14 percent recurrence.

"We assumed that we would observe a 30 percent recurrence rate among the placebo group. It is possible that the placebo juice inadvertently contained the active ingredients that reduce urinary tract infection risk, since both juices contained Vitamin C," explained study author Betsy Foxman, PhD, of the University of Michigan School of Public Health in Ann Arbor.

She added, "Another possibility is that the study protocol kept participants better hydrated, leading them to urinate more frequently, therefore decreasing bacterial growth and reducing urinary tract infection symptoms."