Cranberries May Help Prevent Urinary Tract Infections in Elderly Women

News Author: Laurie Barclay, MD
January 22, 2008 — Cranberries are effective in preventing urinary tract infections in elderly women, but evidence is less clear in the long-term for most populations, according to the results of a Cochrane systematic review published in the January 23 issue of the Cochrane Database of Systematic Reviews.
"Cranberries have been used widely for several decades for the prevention and treatment of urinary tract infections (UTIs)," write Ruth G. Jepson and J.C. Craig. "Cranberries contain a substance that can prevent bacteria from sticking on the walls of the bladder. This may help prevent bladder and other urinary tract infections."
The review authors searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL in The Cochrane Library), and the Internet through January 2007, and they also consulted companies involved in promoting and distributing cranberry products and checked reference lists of review articles and relevant studies.
Ten studies were identified meeting selection criteria of randomized controlled trials (RCTs) or quasi-RCTs that compared the efficacy of cranberry products with that of placebo, juice, or water for prevention of UTIs in all populations. The total number of participants enrolled was 1049.
Two authors independently reviewed and extracted data on methods, participants, interventions and outcomes, which were rates of symptomatic and asymptomatic UTIs, adverse effects, and treatment compliance. Whenever possible, relative risks (RR) were calculated, and when this was not feasible, data were summarized as a narrative synthesis. Cochrane criteria were used to grade the quality of the included trials and evidence.
Of the 10 included studies, 5 were crossover and 5 were parallel group; 7 compared cranberry/cranberry-lingonberry juice with placebo, juice, or water; and 4 studies compared cranberry tablets with placebo (1 study evaluated both juice and tablets).
Compared with placebo or control, cranberry products were associated with significantly reduced incidence of UTIs at 12 months (relative risk [RR], 0.65, 95% confidence interval [CI], 0.46 - 0.90). However, cranberry products were more effective in reducing the incidence of UTIs in women with recurrent UTIs vs elderly men and women or people who required urinary tract catheterization.
The evidence was inconclusive as to whether cranberry products are effective in older men and women, and current evidence suggests that they are ineffective in people with a neuropathic bladder.
The meta-analyses included only 4 studies, because the remaining 6 studies had methodologic issues or were missing data. Only 1 study reported a significant result regarding the outcome of symptomatic UTIs.
In all studies, adverse effects were frequent, and several studies had high rates of dropouts and withdrawals.
Remaining areas of uncertainty include optimal duration of use, dosage, and preparation (eg, juice, tablets, or capsules) of cranberry products.
"There is some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12 month period, particularly for women with recurrent UTIs," the reviewers write. "Its effectiveness for other groups is less certain. The large number of dropouts/withdrawals indicates that cranberry juice may not be acceptable over long periods of time."
The Nuffield Trust gave Ms. Jepson a short-term fellowship for this review. The review authors have disclosed no relevant financial relationships.
Cochrane Database Syst Rev. 2008;00:000-000.