Compounds in cranberries are able to alter E. coli bacteria so that they are unable to initiate an infection. E. coli are responsible for illnesses ranging from kidney infections, to gastroenteritis, to tooth decay.
Beneficial health effects that have long been attributed to cranberries and cranberry juice include, in particular, the ability to prevent urinary tract infections (UTIs).
A new study used an atomic force microscope and other sophisticated tools to study how certain tannins (called proanthocyanidins or PACs), which are found primarily in cranberries, interact with bacteria at the molecular level. The study found that the compounds prevent E. coli from adhering to cells in the body, a necessary first step in infections.
Cranberries also inhibit the ability of E. coli to produce IAA, a molecule that enables bacteria to sense whether or not their population is large enough to initiate an infection.