Cranberry Products Can Prevent UTIs, Large-Scale Review Suggests
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Old Wives’ tales are often considered to be nothing more than folklore, but a new review study suggests there is scientific evidence supporting the use of cranberry products for urinary tract infections (UTIs). The data is published in The Cochrane Database of Systematic Reviews.
The history of cranberries and bladder problems
An estimated 10 in 25 women and 3 in 25 men will experience a UTI during their lifetime. Symptoms – such as a burning sensation while urinating – can be uncomfortable at best, and life-threatening at worst if the infection spreads throughout the body. The standard of care treatment is often a prescription for antibiotics, which can be effective and quick to clear the infection. However, some people experience recurrent UTIs where the infection just keeps coming back.
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For centuries, cranberry juice and products that contain the fruit have been suggested as a “natural” and easily accessible approach to stop infections in their tracks. “Without being sure if or how it [cranberry products] works, some healthcare providers began suggesting it to their patients. It was a harmless, easy option at the time,” explains Flinders University epidemiologist Dr. Jacqueline Stephens, a co-author of the study. “Even centuries ago, Native Americans reportedly ate cranberries for bladder problems, leading somewhat more recently, to laboratory scientists exploring what it was in cranberries that helped and how it might work.” We now know that cranberries contain substances called proanthocyanidins, or PACS, which can prevent bacteria from sticking to the bladder wall.
Improving the quality of previous research
Dr. Gabrielle Williams, epidemiologist at the University of Sydney, led the study alongside scientists at Flinders University and The Children’s Hospital at Westmead. It is the fifth update to a review that was first published in 1998 and later refined in 2003, 2004, 2008 and 2012. The most recent analysis – published in 2012 – explored evidence from 24 trials, and ultimately found no benefit of cranberry products in the context of UTI prevention.
The review published by Williams and colleagues expanded the number of studies analyzed to 50 trials incorporating almost 9,000 participants. “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,” the researchers explain. “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.” From the Register, all randomized controlled trials, or quasi-randomized controlled trials of cranberry products compared to a placebo group were included.
"The studies we looked at included a range of methods to determine the benefits of cranberry products,” explains Stephens. “The vast majority compared cranberry products with a placebo or no treatment for UTI and determined drinking cranberries as a juice or taking capsules reduced the number of UTIs in women with recurrent cases, in children and in people susceptible to UTIs following medical interventions such as bladder radiotherapy.”
Cranberry products reduced risk by 25% in women
The review data suggests that cranberry products can reduce the risk of repeat UTIs in women by over 25%. In children, this figure increases to over 50% and for people at higher risk of developing UTIs after a medical procedure it stands at 53%. No benefits were observed for elderly or pregnant individuals, or for people with issues emptying their bladder. “This incredible result didn’t really surprise us, as we’re taught that when there’s more and better evidence, the truth will ultimately come out,” says Williams.
The researchers emphasize that few participants in the trials described experiencing any side effects while taking cranberry products. Those that did reported tummy pain was the most common incident. The team did not find enough information to state whether cranberry products are more or less effective compared to antibiotics or probiotics in UTI prevention.
“Even back in 1973, my mum was told to try cranberry juice to prevent her horrible and frequent UTIs, and for her it’s been a saviour. Despite me niggling in her ear about evidence, she’s continued to take it daily, first as the nasty sour juice and in recent years, the easy to swallow capsules. As soon as she stops, wham the symptoms are back,” Williams recalls. As usual, it turns out that mum was right! Cranberry products can help some women prevent UTIs.”
While the research suggests cranberry products could be a safe and effective way to prevent reoccurring UTIs, Williams and team note that the optimum dose of cranberry remains to be determined. “Proper standardisation of cranberry products for PAC content and correlation of the PAC content with anti‐adhesion bioactivity may be important to ensure that particular cranberry products contain sufficient PAC to be effective,” Williams and colleagues state.
Reference: Williams G, Hahn D, Stephens J, Craig J, Hodson E. Cranberries for preventing urinary tract infections. CDSR. 2023;(4). doi: 10.1002/14651858.CD001321.pub6
This article is a rework of a press release issued by Flinders University. Material has been edited for length and content.