There is now good evidence that cranberry products can be effective in preventing UTIs. Cranberry does not have any bacteriostatic or bactericidal effects. However a chemical in cranberry products is thought to work by preventing certain bacteria from attaching to cells that line the bladder. Therefore this helps to prevent bacteria from infecting the bladder and so helps to prevent (rather than cure) infection.
A Cochrane Reviewą shows that cranberry juice may decrease the number of symptomatic urinary tract infections (UTIs) over a 12 month period in younger women. There is also a study˛ demonstrating effectiveness in older women; although trimethoprim had a very limited advantage over cranberry extract in terms of UTI free days, it also had more adverse effects.
Some points about cranberry products include:
- You can buy cranberry extracts (capsules, drinks, etc) from supermarkets, pharmacies and health stores.
- NHS Tayside will allow prescribing on GP10 in certain circumstances. See DTC Supplement No 119 Aug/Sept 2012
- The optimum dose is not yet clear. It is thoughtł that a daily dose of a high-strength capsule (containing at least 200 mg of cranberry extract) is best as this is likely to be more effective than drinking cranberry juice.
- Cranberry can react with certain medicines. In particular, it is unsafe to take with warfarin.
References:
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Jepson RG, Craig JC; Cranberries for preventing urinary tract infections. Cochrane Database Systematic Review 2008 Jan 23;(1):CD00132
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McMurdo ME, Argo I, Phillips G et al; Cranberry or trimethoprim for the prevention of recurrent urinary tract infection. J Antimicrob Chemotherapy 2009 Feb;63(2):389-95
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Urinary tract infection (lower) - women, Clinical Knowledge Summaries (October 2009)
