A thorough review of the evidence has found that drinking cranberry juice is unlikely to prevent bladder and kidney infections, experts say today.
Cranberries and cranberry juice have been used to prevent urinary tract infections, such as cystitis, for many years, perhaps because certain compounds in cranberries may prevent bacteria sticking to cells lining the walls of the urinary tract.
Dr Ruth Jepson of the University of Stirling, UK, and her team looked at 24 studies of 4,473 people given cranberry juice in tablets or capsules, or various types of placebo or other non-cranberry treatments.
In some studies there seemed to be a small benefit for women who had recurring infections, but women would have to consume two glasses of cranberry juice per day for long periods to prevent one infection. However, many women in this group stopped drinking the juice every day, suggesting that it may be an unrealistic aim.
So the team concludes that the current evidence does not support cranberry juice as a means of preventing urinary tract infections.
This review updates the previous, 2008, review by adding 14 recent studies. The 2008 review concluded that cranberries "offer a small benefit in preventing recurring urinary tract infections in women".
It is published in The Cochrane Library today (October 17).
Dr Jepson says: "Now that we’ve updated our review with more studies, the results suggest that cranberry juice is even less effective at preventing urinary tract infections than was shown in the last update. We can’t see a particular need for more studies of the effect of cranberry juice, as the majority of existing studies indicate that the benefit is small at best. More studies of other cranberry products such as tablets and capsules may be justified, but only if these products contain the recommended amount of active ingredient."
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