I know this has been kicked around a lot on this board but I thought I'd just post this anyway. Studies have shown that cranberry juice and even blueberry juice prevent E.coli from sticking to the walls of the bladder. http://www.pitt.edu/~cjm6/s99cranberry.html Another study suggested that the tannins in cranberries may actually act as antibacterial agents to treat drug resistant UTI's. http://pda.physorg.com/lofi-news-bac..._77194887.html
Also, a study was conducted that suggested grape juice was just as effective as cranberry juice reducing the incidence of UTI's. http://www.welchs.com/press/utract.html The source is a press release from Welch's (which also performed this study) so take it with a grain of salt.....or pepper,lol.
However, I cannot find any studies that say with a reasonable degree of medical certainty that cranberry pills actually prevent the incidence of UTI's or have any health benefits at all. In fact, one study indicated that taking too many cranberry pills can cause kidney stones. http://www.healthcentral.com/drdean/408/47859.html Cranberry pills have great variation in the amount of cranberry concentrate they contain and the number of pills recommended per day by the manufacturer differ greatly. My sense is that a lot of positive comments about cranberry pills preventing UTI's comes from anecdotal evidence based on manufacturers hype and client testimonials...not science.
Having said that, I'll still be taking my cranberry pills and drinking my cranberry juice. I don't know if the pill dosage is safe or if the cranberry juice I drink definitely helps me but I haven't had a UTI in almost 9 years. Anyway, I thought it was interesting stuff.