Vitamin and Mineral Requirements in Human Nutrition

145 8.1 Nutrients with an antioxidant role The potential beneficial effects of antioxidants in protecting against disease have been used as an argument for recommending increasing intakes of several nutrients above those derived by conventional methods. If it is possible to quantify such claims, antioxidant properties should be considered in decisions concerning the daily requirements of these nutrients. This section examines metabolic aspects of the most important dietary antioxidants—vitamins C and E, the carotenoids, and several minerals—and tries to define the populations which may be at risk of inadequacy to determine whether antioxidant properties per se should be, and can be, considered in setting a requirement. In addition, pro-oxidant metabolism and the importance of iron are also considered. Members of the Food and Nutrition Board of the National Research Council in the United States recently defined a dietary antioxidant as a substance in foods which significantly decreases the adverse effects of reactive oxygen species, reactive nitrogen species, or both on normal physiological function in humans (1). It is recognized that this definition is somewhat narrow because maintenance of membrane stability is also a feature of antioxidant function (2) and an important antioxidant function of both vitamin A (3) and zinc (4). However, it was decided to restrict consideration of antioxidant function in this document to nutrients which were likely to interact more directly with reactive species.