Cranberries: A Natural Remedy to Prevent Urinary Tract Infections
Cranberries contain proanthocyanidins (PACs), which inhibit the adhesion of p-fimbriated Escherichia coli to urothelial cells lining the bladder. Cranberry products have been widely used for several decades to prevent urinary tract infections (UTIs). This is the fifth update of a review first published in 1998 and updated in 2003, 2004, 2008, and 2012.
The objective was to evaluate the efficacy of cranberry products in preventing UTIs in susceptible populations.
Studies in the registry were identified through searches on CENTRAL, MEDLINE and EMBASE, conference proceedings, the International Clinical Trials Registry search portal (ICTRP) and ClinicalTrials.gov.
All randomized controlled trials (RCTs) or quasi-RCTs on cranberry products compared with placebo, no specific treatment or other interventions (antibiotics, probiotics) for prevention of urinary tract infections were included.
Two authors independently evaluated and extracted data.
Information was collected on methods, participants, interventions, and outcomes (incidence of symptomatic urinary tract infections, positive culture results, side effects, adherence to therapy).
Risk ratios (RRs) were calculated with 95% confidence intervals (CIs) where appropriate.
Study quality was assessed using the Cochrane risk of bias assessment tool. Confidence in evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.
At subsequent study update, 26 new studies were added, bringing the total number of included studies to 50 (8857 randomized participants).
The risk of bias for sequence generation and allocation concealment was low for 29 and 28 studies, respectively. Thirty-six studies were at low risk of execution bias and 23 studies were at low risk of detection bias. Twenty-seven, 41, and 17 studies were at low risk of attrition bias, reporting bias, and other biases, respectively.
Forty-five studies compared cranberry products with placebo or no specific treatment in six different participant groups. Twenty-six of these 45 studies could be meta-analyzed for the outcome of symptomatic, culture-verified urinary tract infections.
With moderate evidence of certainty, cranberry products reduced the risk of urinary tract infections.
When studies were divided into groups by treatment indication, cranberry products probably reduced the risk of symptomatic, culture-verified UTIs in women with recurrent UTIs.
Other comparisons were cranberry products with probiotics (three studies) or antibiotics (six studies), cranberry tablets with cranberry liquid (one study), and different doses of PAC (two studies).
Compared with antibiotics, cranberry products may make little or no difference in the risk of symptomatic, culture-verified urinary tract infections or in the risk of clinical symptoms without culture.
Compared with probiotics, cranberry products may reduce the risk of symptomatic, culture-verified urinary tract infections.
This update adds 26 more studies, bringing the total number of studies to 50 with 8857 participants.
These data support the use of cranberry products to reduce the risk of symptomatic, culture-verified urinary tract infections in women with recurrent UTIs, children, and people susceptible to UTIs following surgery.
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