personnel maintain their nutritional status, health, and performance in extreme as well as temperate environments. The MRDA are currently being revised to reflect the 1989 RDAs (NRC, 1989).
The increased energy requirement during cold-weather operations is due to the heavy cold-weather clothing and footgear (the hobbling effect), and increased effort needed for locomotion on snow- or ice-covered terrain (Gray et al 1957; Johnson and Kark, 1947; see Jones and Lee, Chapter 11 in this volume). Energy requirement increases in proportion to the amount of time spent working in the cold; thus, it is dependent on mission. The increased energy allowance does not apply to military personnel stationed in cold climates who are not engaged in field operations.
Even though the MRDAs recommend a minimum of 4,500 kcal/d for military personnel working in the cold, energy requirements for cold-weather field operations are variable and difficult to predict. Studies in which energy expenditure of military personnel working in the cold was measured using stable isotopes showed mean energy expenditures of 4,253 kcal/d (King et al., 1992) and 4,919 kcal/d (Hoyt et al., 1991).
Military rations may be wet packed, i.e., they do not required additional water during preparation, or dehydrated and are divided into group feeding rations and individually packaged rations. Although any military ration may be provided to the soldier while operating in cold environments, some rations may be more suitable than others. Freezing of rations and water, and difficulties associated with preparing and serving hot foods, are inherent problems of cold-weather field feeding.
Group feeding rations are used whenever the opportunity to eat together as a unit is possible. The meals are prepared and served hot to military personnel. Among the group feeding rations, the Tray Pack (T Ration) is the ration most commonly used for cold-weather field feeding because it does not require refrigeration or cooking. The other group feeding rations are: (1) A Ration, which consists of both shelf-stable and perishable food items requiring refrigeration and cooking, and (2) B Ration, which consists of canned and dehydrated food items requiring cooking but no refrigeration. Because of the effects of extreme cold temperatures on the equipment required to maintain and prepare the A and B Rations, these rations are not commonly served during cold-weather field operations.