. "5 The Energy Costs of Protein Metabolism: Lean and Mean on Uncle Sam's Team." The Role of Protein and Amino Acids in Sustaining and Enhancing Performance. Washington, DC: The National Academies Press, 1999.
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The Role of Protein and Amino Acids in Sustaining and Enhancing Performance
Besides the apparent use of the new term without proper attribution was the situation of a Dutch chemist, writing in a Dutch journal, defining a new word in French that was derived from Greek, and then qualifying its meaning in Latin! Further, considering that this episode took place 160 years ago, not only was the mail a lot faster, but also the publication time was substantially shorter than it is today, since the entire story took place in a period of about 3 weeks!
Admittedly, Berzelius and Mulder were right: Protein is the essential general principle of the constituents of the animal body. Thus, one might briefly summarize the physiological roles of protein in metabolism as "responsible for just about everything." But, this is neither particularly helpful nor informative.
FUNCTIONS OF BODY PROTEINS AND AMINO ACIDS
Table 5-1 lists a variety of the functions of body proteins and amine acids. From the practical standpoint of integrative human physiology helpful to the military, the major roles of body proteins are (1) those relating to protein synthesis and protein breakdown in the context of maintaining lean body mass, (2) efficient operation of regulatory proteins required for conduct and optimization of body functions, and (3) the energy costs of the above, including the cost of oxidation and excretion of protein metabolites resulting from the metabolic reactions constituting these events. The net physiological results that are useful to military personnel include increased strength, improved endurance, optimization of "fight or flight" reactions (preferably the former), efficient blood coagulation and wound healing, enhanced immunological functions with improved disease resistance, and peak mental alertness and memory.
What is often forgotten in this context is that protein turnover is an energy-requiring process. Further, the energy cost of protein metabolism is higher than conventionally estimated. These observations are important because one of the principal lessons learned from prior Committee on Military Nutrition Research reports, such as the Ranger studies, is that biological energy demands often far exceed dietary energy intakes in combat field circumstances. Thus, while strength and endurance might immediately be identified with protein metabolism, the energy costs of (1) the protein enzymatic reactions involved in fight or flight reactions, (2) the synthesis of host defense proteins, or (3) memory storage might not be so readily apparent.
PROTEIN METABOLISM AS AN ENERGY-REQUIRING PROCESS
In 1989, Waterlow and Millward calculated the daily energy cost of protein turnover as approximately 18 kJ (4.3 kcal)/kg body weight, or about 20 percent of the basal metabolic rate. This estimate, made from the best information available at the time, tallied the energy costs of protein breakdown and regula-