In 1998, researchers from Rutgers University identified the specific components in cranberries that function as previously suggested. These condensed tannins or proanthocyanidins from the cranberry fruit prevent Escherichia coli (E.coli), the primary bacteria responsible for UTIs, from attaching to cells in the urinary tract. Thus, the bacteria are flushed from the tract rather than being allowed to adhere, grow and lead to infection.