Daily Cranberry Prophylaxis to Prevent Recurrent Urinary Tract Infections May Be Beneficial in Some Populations of Women

TO THE EDITOR—We applaud Dr Barbosa-Cesnik and her colleagues for their excellent contribution to the literature on cranberry juice for the prevention of urinary tract infections (UTIs) [1]. In a population of college women with recent acute UTIs, their clinical trial found no significant difference between the use of cranberry juice and placebo to prevent recurrence of infection. Although Barbosa-Cesnik et al [1] conclude that daily use of cranberry juice did not result in a decrease in the 6-month incidence of a recurrent UTI, we favor a more conservative interpretation, since the study was underpowered to detect a difference between cranberry juice and placebo. In the Methods, the authors state that their sample size calculations were based on an anticipated UTI recurrence rate of 30%. However, the actual observed rate in the placebo arm was only 14%. Therefore, adequate power would have required enrollment of 656 participants, which we realize is a challenging task.