The pooled data from 10 studies comparing cranberry-product consumers against nonusers showed cranberry consumption had a risk ratio protective against UTI at 0.62 (95% CI 0.49 to 0.80), according to Chien-Chang Lee, MD, of the National Taiwan University Hospital, and colleagues.
A subgroup analysis found the cranberry products were more effective in women with recurrent UTI, female populations, children, regular cranberry juice drinkers, and those who used cranberry products more than twice daily, Lee and co-authors wrote in the July 9 issue of Archives of Internal Medicine.
"Cranberry-containing products have long been used as a folk remedy to prevent UTIs," the authors explained. Cranberry is thought to interfere with the attachment of bacteria to uroepithelial cells, potentially preventing infection.
The meta-analysis evaluated randomized controlled trials that compared the effectiveness of cranberry containing products, such as juices and pills, with placebo and non-placebo control groups at preventing UTIs. The review included data from 10 trials of 1,494 patients, with 794 in the cranberry group versus 700 in the control group.
In pooled trials, there was an association with protective effects for the cranberry group and significant heterogeneity between the trials (RR 0.68, 95% CI 0.47 to 1.00), but the results were nonsignificant, Lee and colleagues wrote.
They added that sensitivity analyses "showed that the protective effect of cranberry containing products was stronger in nonplacebo-controlled trials" and suggested that expectations of efficacy had an effect on outcomes.
When broken down by subgroup, there was a nonsignificant trend for protection in certain groups consuming cranberries, including:
- Women with recurrent UTI (RR 0.53, 95% CI 0.33 to 0.83)
- Female patients (RR 0.49, 95% CI 0.34 to 0.73)
- Children (RR 0.33, 95% CI 0.16 to 0.69)
- Cranberry juice drinkers (RR 0.47, 95% CI 0.30 to 0.72)
- Patients consuming cranberry products more than twice daily (RR 0.58, 95% CI 0.40 to 0.84)
The authors noted that patients who drank cranberry juice versus other forms of cranberry may have been better hydrated, and additives in juice may have offered additional protective benefits not seen in cranberry tablets or capsules.
However, the high sugar content in most cranberry drink products may cause gastrointestinal problems or raise concerns about sugar control in diabetic patients, the authors warned.
They concluded that although their meta-analysis showed an association between cranberry product consumption and protection against UTI, "this conclusion should be interpreted with great caution" due to the "substantial heterogeneity across trials."
The authors said that their review was limited by absent searches for conferences, proceedings, and clinical trial registries; inability to reach some study authors to acquire missing data; and missing proanthocyanidin content for cranberry products in several trials. Proanthocyanidins are compounds that may potentially inhibit the adherence of Escherichia coli to urological mucosa, they wrote.
Fuente: Lee CC, et al "Cranberry-containing products for prevention of urinary tract infections in susceptible populations" Arch Intern Med 2012; 172: 988-996.