Diet can play a key role in the pathogenesis of cancer. Diets high in fat and low in fiber predispose individuals to colon cancer. A high-fat diet is also implicated in breast cancer and prostate cancer. The dietary fat-cancer linkage is supported by epidemiological evidence, animal studies, and prospective trials. The antioxidants vitamin E, ascorbic acid, and beta-carotene have a protective effect and act as antipromoters of carcinogenesis. A diet of less than or equal to 10% of calories from fat and less than or equal to 40 g of fiber daily that includes fruits and vegetables will prevent up to 35% of cancers.