Cranberry juice fails to prevent recurrent urinary tract infection: results from a randomized placebo-controlled trial

Abstract

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.

Figure 1.

Disposition of participants in clinical trial of cranberry juice 2 times/day versus placebo. Number of study participants enrolled, allocated, followed, and analyzed shown using CONSORT 2010 Flow Diagram.

Figure 2.

Self-reported compliance with study protocol by treatment group and month. Clinical trial of cranberry juice 2 times/day versus placebo. Otherwise healthy young women (319) with a culture-confirmed urinary tract infection 2005–2007.

Figure 3.

Kaplan Meier curves of survival to urinary tract infection recurrence by juice assignment. clinical trial of cranberry juice 2 times/day versus placebo. Otherwise healthy young women (319) with a culture-confirmed urinary tract infection 2005–2007. The cranberry group had a higher failure rate than placebo (20% vs 14%) but the difference was not statistically significant.

Figure 4.

Risk of a recurring urinary tract infection (UTI) by history of UTI and juice assignment. Participants (92/155) taking cranberry and taking placebo (87/164) reported a history of one or more UTI. Error bars show 95% confidence intervals. Clinical Trial of Cranberry Juice 2 times/day versus placebo. Otherwise healthy young women (319) with a culture-confirmed urinary tract infection 2005–2007.