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March 9, 1994

Reduction of Bacteriuria and Pyuria After Ingestion of Cranberry Juice

JAMA. 1994;271(10):751-754. doi:10.1001/jama.1994.03510340041031

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)