STIRLING researcher, Dr Ruth Jepson, has concluded that cranberries do not prevent urinary tract and bladder infections such as cystitis, and that any benefit, if present at all, is likely to be small and only for women with recurrent urinary tract infections (UTI).
Cranberries and cranberry juice have been used to prevent UTIs for decades, although it is not clear how they might help protect against infection. According to one theory, certain sugars and flavanol compounds in cranberries prevent bacteria sticking to cells lining the walls of the urinary tract.
Dr Jepson and her colleagues gathered evidence from 24 studies involving a total of 4,473 people. Those in treatment groups were given cranberry juice, tablets or capsules, while those in control groups were given placebo cranberry products, water, methenamine hippurate, antibiotics, lactobacillus or nothing.
Dr Jepson says: “The results suggest that cranberry juice is even less effective at preventing UTIs than was shown in our previous research.
“In the studies where participants were given juice, there were large numbers of drop-outs, suggesting it might not be easy to drink over long time periods. A common problem with studies evaluating cranberry tablets or capsules was that they rarely reported the amount of active ingredient, so it was unclear whether levels would have been high enough to have any effect.”
Although in some studies there were small benefits for women suffering from recurring infections, women would have to consume two glasses of cranberry juice per day for long periods to prevent one infection. The researchers conclude that current evidence does not support cranberry juice as a means of preventing UTIs.
“We can’t see a particular need for more studies of the effect of cranberry juice,” says Dr Jepson, “as the majority of existing studies indicate that the benefit is small at best, and the studies have high drop-out rates.
“More studies of other cranberry products, such as tablets and capsules, may be justified, but only for women with recurrent UTIs, and only if these products contain the recommended amount of active ingredient.”
Dr Jepson’s research is published in The Cochrane Library, which produces high quality healthcare information, and this update was funded by the NHS National Institute of Health Research.
Further information from Patricia Hess at firstname.lastname@example.org or 01786 466 687
Notes for editors
Full citation: Jepson RG, Williams G, Craig JC. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews 2012, Issue 10. Art. No.: CD001321. DOI: 10.1002/14651858.CD001321.pub5.
URL upon publication: http://doi.wiley.com/10.1002/14651858.CD001321.pub5
Dr Ruth Jepson is co-director of the Centre for Public Health and Population Health Research at the University of Stirling
Contact: Patricia Hess