question, it appears that rehydration is necessary in humans before depressed food intake returns to normal. To maximize the energy intake of military personnel in hot environments in which significant physical activity is required, maintenance of adequate hydration status should be a primary objective of all policies related to soldier readiness. Maintenance of states of proper hydration was also identified as the most critical issue facing soldiers in desert environments in an Army report on food management issues written during Operation Desert Storm (Norman and Gaither, 1991). The recent CMNR report Fluid Replacement and Heat Stress (Marriott and Rosemont, 1991) thoroughly addressed this issue.
Is there any scientific evidence that food preferences change in hot climates?
Several animal studies document changes in food preferences in hot environments. There are also a limited number of studies that show decreased caloric intake in humans when working in a hot environment. Most of these studies did not allow for acclimatization of subjects to the hot climate. In the one major study that did, food intake decreased less markedly in the acclimatized individuals, with no change in percent distribution of kilocalories from fat, carbohydrate, or protein. In the summer season food choices do change, but whether this is due to environmental temperature or other factors such as price and availability has not been well established. Thus, to date, most information on changes in food preferences in humans is limited to anecdotal observations or studies that were not balanced with respect to temporal adaptation to climatic change.
Are there special nutritional concerns in desert environments in which the daily temperature may change dramatically?
If rations are consumed in adequate amounts, no specific nutrient concerns need be addressed as a result of the dramatic changes in temperature that frequently occur in the desert. Adequate intake of fluid to avoid dehydration and help maintain food intake is obviously important. The levels of nutrients specified by the MRDAs appear to be adequate to meet the nutrient needs of soldiers if rations are consumed in appropriate amounts.
Is there an increased need for specific vitamins or minerals in the heat?
Although small increases may occur in the losses of B vitamins in sweat during work in hot environments, these losses do not appear to be great enough to justify increasing the requirement over that established in the MRDAs. There is limited evidence that vitamin C may have an effect in reducing heat stress during periods of acclimatization, particularly if the individual has had a low vitamin C intake prior to exposure to the heat.