Does cranberry juice prevent urinary tract infections?

Chris - Cranberry juice is very good for preventing and treating urinary tract infections. The reason for that is that there is a chemical in cranberry juice which down-regulates a chemical on the surfaces of cells which line the urinary tract - in other words, all the way from the kidney, right out to the outside world. It turns off, on the cells that line that pathway, a molecule which is a mannose sugar linked to some other bits of protein, which E. coli, the most common cause of urine infections, like to cling to. So, if you down-regulate the expression of that chemical on the cell surface, it gives you "anatomical Teflon". It makes you very slippery inside so the bacteria can't cling on; and as a result, they're more likely to be washed out every time we have a wee. And so, therefore, cranberry juice is very effective at reducing either the initial occurrence of a urinary tract infection, but also, it's very good at preventing it coming back and treating it as well.