Cranberry-Containing Products For Prevention Of Urinary Tract Infections In Susceptible Populations: Systematic Review And Meta-analysis of Randomized Controlled Trials, Archives Of Internal Medicine, 9 July 2012
It reviewed 13 trials, 1616 subjects, and found:
"Our findings indicate that cranberry-containing products are associated with protective effect against urinary tract infections (UTIs)."Reading this gives me a greater appreciation for the effort behind study design. When do you count someone as having a UTI? When their urine sample contains 1,000 colony-forming units or 10,000? Or do you just look at symptoms? What do you use as a placebo? If you use something that is colored red and add some ascorbic acid for tartness, perhaps the ascorbic acid also prevents UTI. If the placebo is not also a beverage, just the extra hydration from drinking cranberry juice could be protective (in fact, staying hydrated with just water has shown to be protective). How much do you give, and how long do you give it?
To me, trying to make sense of all these variables puts the fun into science. And science here has revealed there is at least one type of compound in cranberries, proanthocyanidins, that prevent E. coli bacteria from sticking to the walls of the bladder and urinary tract.
But the effect is temporary, lasting maybe 8 hours. You have to ingest cranberry at least twice a day, every day. And this study found that cranberry juice was better than cranberry capsules or tablets, so the cranberry you ingest comes packaged, likely, with a lot of sweetener. You're up against the cost in both dollars and calories, and of course getting it down someone who doesn't like the taste. In some people cranberry juice causes gastrointestinal distress.
If you can get past these obstacles, you have yourself a pretty tasty (to me) and effective way to prevent UTIs. It should be the beverage of choice in care homes!