Vitamin A is also a powerful antioxidant and can prevent the formation of free radicals. Although vitamin A-rich fruits and vegetables are considered to be protective against certain cancers, vitamin A supplements are not recommended. Vitamin C blocks the formation of carcinogenic nitrosamines in the digestive tract. Vitamin C also acts as an antioxidant by preventing the oxidation of certain chemicals to active carcinogens. Rich food sources of vitamin C are citrus fruits, berries, and most dark-green vegetables like broccoli, spinach, and green peppers.
Dietary fiber is the non-digestible or partially digestible materials found in plant cells.
Holding onto water in the intestinal tract, increasing stool bulk, which may dilute carcinogen concentration in the colon. Binding with bile acids in the intestinal tract, some of which could convert to co-carcinogens. Besides decreasing cancer risk, eating more fruits, vegetables, and less fat will also help reduce the risk of heart disease, high blood pressure, and diabetes. The National Academy of Sciences, U.S. Department of Agriculture, and the National Cancer Institute all recommend that 5 or more servings of fruits and vegetables be eaten every day to reduce the risk of cancer and other chronic diseases and maintain good health. Both recommend that Americans eat between 5 and 9 servings of fruits and vegetables every day.