Efficacy of Dietary Antioxidants to Prevent Oxidative Damage and Inhibit Chronic Disease

Many in vitro studies have shown that dietary antioxidants, such as vitamin C (ascorbic acid), vitamin E ( tocopherol), s-carotene, and flavonoids, act as effective antioxidants in biological systems such as plasma, lipoproteins, and cultured cells (1–3). For example, vitamin C effectively inhibits lipid and protein oxidation in human plasma exposed to various (patho)physiologically relevant types of oxidative stress, such as activated polymorphonuclear leukocytes, reagent or myeloperoxidase-derived hypochlorous acid, cigarette smoke, or redox-active iron or copper ions (1,3). Vitamin E is the most abundant lipid-soluble antioxidant in human lipoproteins and tissues and acts as a chain-breaking antioxidant against lipid peroxidation (3). scarotene, lycopene, lutein, and other carotenoids and oxy-carotenoids are efficient singlet oxygen quenchers and, thus, may be important in protecting the eye and skin against UV-induced oxidative damage (2,5). These small-molecule dietary antioxidants interact with each other in an "antioxidant network" and complement antioxidant enzymes and metal-binding proteins present in cells and extracellular fluids.