These databases include the U.S. Department of Agriculture's National Nutrient Databank, the Canadian Nutrient File, and other databases that contain a nationally representative sample of foods com- monly eaten in the United States or Canada and that report concentrations for the antioxidant of interest and others. It is recognized that limitations exist in the use of food composition databases to accurately estimate intakes. An explanation of the bio- chemical and physiological mechanisms of these adverse effects follows. Role of ROS and RNS in Health and Disease ROS and RNS are produced metabolically by the body. Various compounds in the human body generate free radicals in their metabolism.
Examples are catecholamines and compounds found in the mitochondrial electron-transport chain.
In addition, activated phagocytes produce ROS as one of the defense mechanisms they use to kill microbes. Thus, in this situation, ROS are used by the body as a defense mechanism against infection. A considerable body of biological evidence shows that ROS and RNS can damage cells and other body components and could in theory contribute to dys- function and disease states. The mechanisms of antioxidant action for decreasing the adverse effects of ROS or RNS are varied. Some antioxidants remove free radicals by reacting directly with them in a noncatalytic manner before the radicals react with other cell components.