required to function in these extreme conditions. These micronutrients are no less important than is oxygen. It just takes longer to become deficient in them than it does for oxygen.

In the past, U.S. Army recommendations regarding micronutrient intake for work in cold and high-altitude environments have been limited to three areas of consideration. They have suggested the need for increased requirements for vitamins and minerals to accommodate the caloric requirement of cold and high-altitude operations; a high altitude-induced increase in the requirement for vitamins A, E, and C, specifically; and the need for caution in the use of vitamin and mineral supplements to attempt to prevent cold stress (Thomas et al., 1993a, b; Askew, 1989). However, increased intakes have not been recommended.

Under any environmental condition, it is necessary to measure accurately intake, excretion, and several indices of status to determine nutrient requirements. A complete set of these indices has not been measured for any of the vitamins or minerals for persons living or working in the cold or at high altitudes. Therefore, it is not possible to report here the actual requirements for any of these micronutrients as affected by prolonged exposure to cold or high-altitude environments.

The approach used in this chapter will be to present a short statement on the major role of each vitamin and mineral in human metabolism, followed by a review of reported dietary intakes or status in various populations living or working in cold climates or at moderate to high altitudes. Finally, for each vitamin and mineral, a micronutrient intake goal will be suggested and compared to the current Recommended Dietary Allowance (RDA) (NRC, 1989), the Military Recommended Dietary Allowance (MRDA) (AR 40-25, 1985), and the anticipated intake of each nutrient provided by the Ration, Cold Weather (RCW) as formulated by the U.S. military. Each micronutrient intake goal has been derived by the author from a systematic reading of the relevant published literature and from personal consideration of widely-accepted, general nutrition principles.

Construction of the micronutrient intake goals assumes that the individuals using it are in generally good health and nutrient status prior to beginning the expedition or maneuver. Thus, the aim of the micronutrient intake goals is to keep the individuals healthy rather than to make them healthy. Construction of the micronutrient intake goals should not be constrained by the limitations of the micronutrient availability from foods in the amount normally consumed. Therefore, use of the terms dietary or dietary intake as they relate to the micronutrient intake goals are not necessarily appropriate.