Background. A number of observational studies and a few small or open randomized clinical trials suggest that
the American cranberry may decrease incidence of recurring urinary tract infection (UTI).
Methods. We conducted a double-blind, placebo-controlled trial of the effects of cranberry on risk of recurring
UTI among 319 college women presenting with an acute UTI. Participants were followed up until a second UTI or
for 6 months, whichever came first. A UTI was defined on the basis of the combination of symptoms and a urine
culture positive for a known uropathogen. The study was designed to detect a 2-fold difference between treated and
placebo groups, as was detected in unblinded trials. We assumed 30% of participants would experience a UTI during
the follow-up period.
Results. Overall, the recurrence rate was 16.9% (95% confidence interval, 12.8%–21.0%), and the distribution
of the recurrences was similar between study groups, with the active cranberry group presenting a slightly higher
recurrence rate (20.0% vs 14.0%). The presence of urinary symptoms at 3 days, 1–2 weeks, and at >1 month was
similar between study groups, with overall no marked differences.
Conclusions. 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.