Can cranberry juice help urinary infections?

28 July 2015



Louise called the show to ask whether cranberry juice can help prevent urinary tract infections, as she had been told, or whether it was simply an old wives' tale


Louise - I've been diagnosed with a kidney infection, which has been caused a urinary infection, which is quite common in women. The one thing that I keep getting told is drink lots of cranberry juice to help prevent me from getting water infections in the future. I'm just wondering if there's anything scientific behind that or is it just an old wives' tale.

Chris - People have looked at this and there's some suggestion that what cranberry juice does is, it does get filtered into the urine, and it changes some of the molecules that are present on the surfaces of the urinary tract. When someone gets a urine infection, usually, it's E. coli - our old friend E. coli. It's a gut bug that crawls into the wrong place. And it does that by clinging on to the walls of your urinary tract by expressing what they ironically call, 'p pili'. These are effectively molecular grappling hooks that make the bacterium sticky. There's evidence that cranberry juice might be able to give you the anatomical equivalent of Teflon so that you become a bit slippery and the E. coli can't cling on. Now, the jury is out actually. People have done a number of studies on this. Some trials show that it is effective. Other trials show that it isn't effective. So, at the moment, I don't think people judge this to be adequate evidence base for us to say this will prevent you getting a UTI. What's certainly and arguably true though is, if you drink plenty and you pee plenty, you will therefore increase the odds of detaching the microbes from where they shouldn't be and flush them out. That means that you're less likely to have a urine infection in the first place. Getting dehydrated, especially on hot days, when you can get an overgrowth of the bugs because you're not washing them out as frequently, that's a big risk factor. So, I would urge you, if you are at risk of having UTIs, which can happen because it's very common, then drinking plenty regardless of what's in the drink you drink - within reason (!) - will probably help.


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