Mechanisms of action of antioxidants as exemplified in vegetables, tomatoes and tea.

Most chronic diseases, including coronary heart disease and many types of cancer depend on the in vivo conversion of cellular macromolecules or of carcinogens to specific reactive, oxidized forms. For that reason, health promoting nutrition involves the daily intake of five to 10 vegetables and fruits, fruit juices, red wine and tea that are rich sources of micronutrients with antioxidant properties, including the antioxidant vitamins C, E and beta-carotene. Tomatoes contain lycopene, a stable, active antioxidant. Many vegetables contain quercetin and related polyphenolic compounds. Tea is a source of epigallocatechin gallate, in green tea, and theaflavin and the associated thearubigins, in black tea. Red wine contains resveratrol. The diverse antioxidants in foods, red wine and tea provide the necessary antioxidant resources for the body to control oxidation reactions in the body with possible adverse consequences. For example, the oxidation of low density lipoprotein (LDL) cholesterol yields a product that damages the vascular system. Thus, a lower intake of saturated fats to decrease the levels of LDL cholesterol, together with an adequate intake of antioxidants, is the optimal approach to lower heart disease risk. Cancer of the stomach involves the consumption of salted, pickled foods yielding direct-acting carcinogens, and their formation is inhibited by vitamins C and E. Cancer in the colon, breast, prostate and pancreas may be caused by a new class of carcinogens, the heterocyclic amines, formed during the broiling or frying of creatinine-containing foods, including fish and meats. Their formation and action can be inhibited by antioxidants such as those in soy, tea, vitamin C and also by the synthetic antioxidants BHA or BHT. The growth, cell proliferation and development of abnormal preneoplastic and neoplastic cells also involves oxidation reactions, including the formation of active oxygen or peroxy compounds. Such reactions can be inhibited by antioxidants, such as those in tea, tomatoes or vegetables. Even ageing and longevity in good health would be favoured by the availability of adequate amounts of varied antioxidants. Prevention of the formation and of action of reactive products by antioxidants as present in fruits, vegetables, tomatoes, red wine and tea is of great public health importance in decreasing the risk of major diseases. Prevention is the optimal approach to disease control, and also as an effective route to lower costs of medical care.