Cranberries for preventing urinary tract infections

Background Cranberries contain proanthocyanidins (PACs), which inhibit the adherence of p‐fimbriated Escherichia coli to the urothelial cells lining the bladder. Cranberry products have been used widely 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. Objectives To assess the effectiveness of cranberry products in preventing UTIs in susceptible populations. Search methods We searched the Cochrane Kidney and Transplant Specialised Register up to 13 March 2023 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register Search Portal (ICTRP) and ClinicalTrials.gov. Selection criteria All randomised controlled trials (RCTs) or quasi‐RCTs of cranberry products compared with placebo, no specific treatment or other intervention (antibiotics, probiotics) for the prevention of UTIs were included. Data collection and analysis Two authors independently assessed and extracted data. Information was collected on methods, participants, interventions and outcomes (incidence of symptomatic UTIs, positive culture results, side effects, adherence to therapy). Risk ratios (RR) with 95% confidence intervals (CI) were calculated where appropriate. Study quality was assessed using the Cochrane risk of bias assessment tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Main results For this update 26 new studies were added, bringing the total number of included studies to 50 (8857 randomised 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 performance 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 bias, respectively. Forty‐five studies compared cranberry products with placebo or no specific treatment in six different groups of participants. Twenty‐six of these 45 studies could be meta‐analysed for the outcome of symptomatic, culture‐verified UTIs. In moderate certainty evidence, cranberry products reduced the risk of UTIs (6211 participants: RR 0.70, 95% CI 0.58 to 0.84; I²