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The Role of Protein and Amino Acids in Sustaining and Enhancing Performance (1999)
Institute of Medicine (IOM)

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. "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-

Page
110
Front Matter (R1-R18)
Executive Summary (1-16)
I Committee Summary and Recommendations (17-18)
1 Committee Review (19-76)
2 Responses to Questions, Conclusions, and Recommendations (77-82)
II Authored Papers and Workshop Discussions (83-84)
3 Protein and Amino Acids: Physiological Optimization for Current and Future Military Operational Scenarios (85-92)
4 Overview of Garrison, Field, and Supplemental Protein Intake by U.S. Military Personnel (93-108)
5 The Energy Costs of Protein Metabolism: Lean and Mean on Uncle Sam's Team (109-120)
6 Regulation of Muscle Mass and Function: Effects of Aging and Hormones (121-136)
7 Effects of Protein Intake on Renal Function and on the Development of Renal Disease (137-154)
8 Infection and Injury: Effects on Whole Body Protein Metabolism (155-168)
9 Inherent Difficulties in Defining Amino Acid Requirements (169-216)
10 Amino Acid Flux and Requirements: Counterpoint Tentative Estimates are Feasible and Necessary (217-242)
11 Physical Exertion, Amino Acid and Protein Metabolism, and Protein Requirements (243-254)
12 Skeletal Muscle Markers (255-278)
13 Alterations in Protein Metabolism Due to the Stress of Injury and Infection (279-284)
Discussion I (285-288)
14 Amino Acid and Protein Requirements: Cognitive Performance, Stress, and Brain Function (289-308)
15 Supplementation with Branched-Chain Amino Acids, Glutamine, and Protein Hydrolysates: Rationale for Effects on Metabolism and Performance (309-330)
16 Dietary Supplements Aimed at Enhancing Performance: Efficacy and Safety Considerations (331-340)
Discussion II (341-346)
Appendixes (347-348)
A Workshop Agenda (349-352)
B Biographical Sketches (353-368)
C Acronyms and Abbreviations (369-372)
D Proteins and Amino Acids - A Selected Bibliography (373-410)
E Protein and Energy Content of Selected Operational Rations (411-412)
Index (413-429)