specific amine acid supplements may provide a decisive advantage in such high-stress scenarios, including improved resistance to disease, preservation of muscular strength through maintenance of muscle tissue, and optimal cognitive performance even in the face of intense stressors.
One of the near-term requirements is to produce a limited-use operational ration that supports optimal cognitive and physical metabolic function while promoting utilization of the soldier's existing fat stores. This ration could be useful in short-duration, direct-action missions and in survival kits (Jones et al., 1993). Such a ration is not a new concept in military nutrition research; nearly 20 years ago, Consolazio and his colleagues (1979) asked:
Would a planned ration of 600 kcal, if consumed, be more beneficial to the soldier than the remnants of a 3600 kcal ration, the majority of which was indiscriminately discarded because of its heavy weight?
Consolazio's studies reiterated previous findings that 100 g of glucose and some electrolytes were important constituents of such a limited-use ration just to ensure minimal function (Taylor et al., 1957). Within the past 3 years, carbohydrate drink and food bar supplements have been developed because of the clearly demonstrated benefits to military performance (Murphy et al., 1994). Current scientific advances may now allow us to consider the specific protein and amine acid content that could be sustaining and even enhancing. The purpose of this review by the Committee on Military Nutrition Research is to evaluate the state of knowledge from basic research and suggest promising research directions in protein and amine acid modulation of military performance in stressful operational scenarios.
The principal operational ration, the Meal, Ready-to-Eat (MRE), is highly fortified in protein (providing 2 g/kg body weight [BW]/d for the typical 75 kg male soldier). This ensures that the estimated daily requirement for protein is met even by Ranger students subsisting largely on MREs but offered less than a full daily ration. Thus, even with an average dally deficit of 1200 kcal/d for 8 weeks, Ranger students still average in excess of 100 g of protein/d (Moore et al., 1992). Although more sensitive markers of protein status such as circulating insulin-like growth factor-I and retinol-binding protein were markedly suppressed during periods of reduced food intake (Nindl et al., 1997), the soldiers developed no clinical, biochemical (e.g., serum protein and albumin), or gross physiological signs of protein deficiency (Martinez-Lopez et al., 1993). The Ranger students also lost a considerable amount of lean mass, although the proportion lost was inversely related to initial fat energy stores (Friedl et al., 1997). The question remains whether a higher protein diet or a carefully crafted supplement could provide any protection to lean mass in comparison with a group receiving the same total (and deficient) calories. A possible approach may come from consideration of factors altered in exercise, which have been