Reduction of Bacteriuria and Pyuria After Ingestion of Cranberry Juice

Abstract

Objective. —To determine the effect of regular intake of cranberry juice beverage on bacteriuria and pyuria in elderly women. Design. —Randomized, double-blind, placebo-controlled trial. Subjects. —Volunteer sample of 153 elderly women (mean age, 78.5 years). Intervention. —Subjects were randomly assigned to consume 300 mL per day of a commercially available standard cranberry beverage or a specially prepared synthetic placebo drink that was indistinguishable in taste, appearance, and vitamin C content but lacked cranberry content. Outcome Measures. —A baseline urine sample and six clean-voided study urine samples were collected at approximately 1-month intervals and tested quantitatively for bacteriuria and the presence of white blood cells. Results. —Subjects randomized to the cranberry beverage had odds of bacteriuria (defined as organisms numbering ≥10⁵/mL) with pyuria that were only 42% of the odds in the control group (P=.004). Their odds of remaining bacteriuric-pyuric, given that they were bacteriuric-pyuric in the previous month, were only 27% of the odds in the control group (P=.006). Conclusions. —These findings suggest that use of a cranberry beverage reduces the frequency of bacteriuria with pyuria in older women. Prevalent beliefs about the effects of cranberry juice on the urinary tract may have microbiologic justification. (JAMA. 1994;271:751-754)