Vitamins and Related Dietary Antioxidants

Abstract

Reactive oxygen species such as superoxide radicals, hydroxyl radicals, hydrogen peroxide, and lipid hydroperoxide are injurious to cellular constituents. Normally, the metabolic machinery of the cell is able to prevent or revert most of the adverse effects of oxidative stress. Vitamins and related compounds may directly or indirectly be involved in one or more stages of cellular antioxidant defense. They may interact with oxidants or oxidizing agents directly (e.g., ascorbic acid), scavenge free radicals and singlet oxygen (e.g., vitamin E, ascorbic acid and beta-carotene), be involved in the removal or separation of transition metals from the specific site of action by chelators or via membrane barrier, or participate in the repair or replacement of damaged molecules and cells by biosynthetic and other processes (e.g., vitamin A and B vitamins). Certain vitamins can act synergistically, or antagonistically, according to the levels or activities of other antioxidant defense systems involved. Many vitamins are interrelated and appear to act compensatorily or complimentarily with the others in different stages of the overall antioxidant defense.