The Clear Science staff recently read a couple of articles about researching a scientific basis for the widely-believed health benefits of cranberry juice. Cranberry juice is renowned for preventing urinary tract infections (UTIs), and there is evidence that it hinders E. coli attachment to cells in the urinary tract. Also, molecules found in cranberries can chelate or bind iron atoms. They do this because they have a lot of phenolic OH group on them. Lone pairs on the oxygens chelate positive metals (chelate means “hold like a claw”). This could remove extra iron from your system.
But these theories are not without counter-evidence. The residence time of cranberry components in your system after you drink them is low. Some argue that to make a real difference, they would have to stick around much longer, or you would have to drink a lot of juice.