Native to North America, cranberries have been used as a medicinal agent for centuries. Cranberries contain proanthocyanidins, which have been shown to inhibit the fimbrial adhesion of bacteria, including Escherichia coli, to the urinary tract epithelium, hence preventing bacterial proliferation and infection. These unique proanthocyanidin compounds, and not acidification of the urine, are suggested to be pivotal in preventing urinary tract infections (UTI).