The cranberry is believed to have a beneficial effect on the bladder and to prevent infections of the bladder. The berry contains antioxidants, such as proanthocyanidines, that prevent harmful microorganisms from attaching to human cells. For example, the cranberry is believed to make it difficult for the e.coli bacterium to adhere to the walls of the bladder and urinary tract, and prevents h.pylori, a bacterium that is held responsible for causing stomach ulcers, from attaching to the stomach wall and causing damage.
It is even claimed that the cranberry is able to fight off certain strains of the influenza virus. The cranberry has also been linked with memory – the berry is claimed to prevent eye fatigue, for example. Wikipedia reports that the cranberry is able to prevent tooth plaque, as well as stomach ulcers. For this reason, cranberry is added to many dietary supplements.
Note: berries cannot replace medicines. Read the footnote below the blueberry description.