Researchers at the University of Michigan School of Public Health, in Ann Arbor, recorded the effects in college women presenting with an acute urinary tract infection (UTI).

First, the details.

• 319 college women presenting with an acute UTI were assigned to a treatment group and followed until a second UTI or for 6 months, whichever came first.
  • A cranberry treatment group: drinking 8 oz of 27% cranberry juice twice daily
  • A placebo group
• UTI was defined on the presence of symptoms and a urine culture positive for a known pathogen.
• The study was designed to detect a 2-fold difference between treated and placebo groups.
• The researchers assumed 30% of participants would experience a UTI during follow-up.
• Neither the patients nor researchers knew the treatment given — double blind.

And, the results.

• Overall, the recurrence rate was 17%.
• Distribution of recurrence was similar between treatments.
• The cranberry group had a slightly higher recurrence rate (20% vs 14%).
• The presence of urinary symptoms at all times during the study was similar between treatments, with overall no marked differences.
• Adjusting for the frequency of sexual activity in the previous month and a history of UTI made no difference in the risk of recurrence by treatment.

The bottom line?

The authors concluded, “Among otherwise healthy college women with an acute UTI, those drinking 8 oz of 27% cranberry juice twice daily did not experience a decrease in the 6-month incidence of a second UTI, compared with those drinking a placebo.

Regarding other studies that reported positive results with cranberry juice, the authors counter that “these studies were not blinded or were underpowered (insufficient participants to detect a real difference).”

Other categories of patients have been studied, and many of the results are summarized here.

This study was supported by a grant from the National Center for Alternative Medicine at the National Institutes of Health.

1/20/11 20:34 JR