For decades, thousands of Danes and particularly women have drunk litres of cranberry juice in order to prevent urinary tract infections (UTI) – but a new survey from The Cochrane Library now shows the juice has no effect.

The suggestion that cranberry juice prevents urinary tract infections has been based on the hypothesis that certain types of sugars and antioxidant flavonoids in cranberries prevent bacteria from attaching themselves to urinary tracts.

The claim has not been an empty one – certain previous surveys have suggested an effect. But the latest survey of the scientific literature shows previous studies to have been such a small section of the overall literature that cranberry juice is found to have pretty much no effect at all.

The latest study looked at a total of 4,473 cases in 24 studies, 14 of which have been carried out since the previous Cochrane survey in 2008. That survey showed a minor positive prophylactic effect in women with recurrent UTI.

“Now that we have updated our survey using more studies, the results seem to show that cranberry juice is less effective in preventing UTI,” says researcher Ruth Jepson at the University of Stirling in Scotland.

She adds that there is no longer any need for more surveys on the effect of cranberry juice, and that with the 2012 survey researchers find it unlikely that the juice can prevent UTI.

Jepson says, however, that studies of other cranberry products such as tablets and capsules, may be worthwhile.

“But only for women with recurrent UTI and only if the products…contain a recommended amount of cranberry,” Jepson says.

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