Cranberry juice has been a traditional remedy for urinary tract infections (UTIs) for many years. Now we know more about the science as to how cranberries work their magic.
Research has determined that chemicals called proanthocyanides do a slick job of preventing germs from adhering to urethra and bladder walls. Cranberries are not the only food that contain proanthocyanides, but they seem to offer the best protection against urinary tract infection.
According to Lisa Barg, writer for Alternative Medicine, it's not necessary to insist on unsweetened cranberry juice. She says there are many studies that indicate that sweetened juice does the same job on UTIs as unsweetened.
"UTIs can be caused by a number of different germs but the most common—by far—is the fecal bacteria E. coli. Inadequate cleaning of the anal area or improper wiping (like going from back-to-front instead of from front-to-back) after bowel movements can help move germs from the rectal area to the urethra."
http://www.lisabarger.com/health-news/cranberry-juice-still-best-for-uti.html