How does Cranberry juice help in preventing and treating Urinary Tract Infection (UTI)?

It has been now known since the mid 1990's that the presence of specific compounds called condensed tannins (esp. proanthocyanidins or PAC) in the Vaccinium fruit species like the Cranberries, Blueberries, Red huckleberries, and lingonberries prevents the attachment of the P fimbriae of Uropathogenic Escherichia coli or UPEC to the urothelium or the inner lining of the urinary tract.

With the use of nanotechnology in medicine, it is now possible to visualize the nanoworld with the use of scanning Atomic Force Microscope or AFM. Atomic Force Microscopic image of E. coli can be seen by clicking the hyperlink.

The PAC's in the Cranberry juice changes in the shape of the surface of E. coli and prevents this bacteria from latching to the inner lining of the urinary tract (urothelium). This inturn prevents bacterial proliferation and infection as the bacteria latches on to the urothelium to secure itself and prevent being flushed by typical urine flow. In the presence of cranberry juice (which contains PAC) the force or strength of E. coli's bonding or the latching to the urothelium is decreased to the point that it is easily flushed out by the urinary flow.