Chemicals present in cranberries prevent infection-causing bacteria from attaching to the cells that line the urinary tract. It was previously thought that the acidity of cranberry juice caused the effect.
Adhesion of bacteria to cells lining the urinary tract is the first step in the development of a urinary tract infections (UTIs). Chemicals found in cranberry products called proanthocyanidins (PACs) prevent E. coli, which is the cause of about 85 percent of UTIs, from adhering to these urinary tract epithelial cells by affecting the surface properties of the bacteria.
Researchers exposed E. coli grown in culture to either light cranberry juice cocktail or cranberry PACs and measured the adhesion forces between the bacteria and a silicon surface using atomic force microscopy. They demonstrated that the longer the bacteria were exposed to either the cranberry juice or the PACS, the greater the decrease in bacterial attachment.