Polyphenols are chemicals found in plants that are believed to have important health benefits, according to the American Cancer Society. Some evidence exists that polyphenols help prevent health dangers such as cancer, high blood pressure, heart disease and diabetes. Foods high in beneficial polyphenols include red cabbage, berries, red and purple grapes, broccoli, radishes, tea and apples. So far, there is no conclusive research about the benefits of polyphenols. Experts advise consuming a balanced diet rich in fruits, beans and vegetables.