Committee on Military Nutrition Research: Activity Report 1992-1994 (1994)

Maximizing soldier performance, an important goal of all the military services, has been largely based on improving the training of personnel and the equipment they use and carry, and by improving military doctrine. However, today's soldiers face increasing demands, both physically in the loads they must carry and mentally in the cognitive abilities required to use the more sophisticated weaponry; both sets of factors place additional burdens on their nutritional needs. Military personnel in combat settings endure highly unpredictable timing and types of stresses as well as situations that require continuing vigilance for hours or days. Soldiers who consume the standard military rations are presumed to be in a state of good nutrition, especially given the liberal Military Recommended Dietary Allowances (MRDAs) (AR 40-25, 1985). But might special rations containing greater amounts of particular nutrients or other food components enhance performance—by improving performance above baseline levels or avoiding a reduction in performance during stress (such as experienced in battle situations) or both?

Substances that may optimize physical performance are often referred to as ergogenic aids. They can be aggregated into five categories: (1) mechanical, (2) psychological, (3) physiological, (4) pharmacological, and (5) nutritional. Foods and food components as ergogenic aids fall into the latter two categories. They may exert their actions by (1) acting as central or peripheral stimulants, (2) increasing the storage or availability of limiting substrates, (3)

acting as a supplemental fuel source, (4) reducing or neutralizing metabolic by-products, and (5) enhancing recovery.

The CMNR was asked to assist a collaborative developmental program between scientists at the U.S. Army Research Institute of Environmental Medicine (USARIEM) and the U.S. Army Natick Research, Development and Engineering Center (NRDEC) by evaluating the performance-enhancing capabilities of food components—specifically tyrosine, other amino acids, complex carbohydrates, caffeine, carnitine, choline, and long-chain fatty acids. The Committee was asked to indicate which if any of these food components offered the most promise for future research that could lead to the development of prototype ration components for testing in laboratory and controlled field settings. In addition, it was asked to address six general questions dealing with enhancement of performance, summarized as follows:

• Is enhancement of physical and mental performance in normal, healthy, young soldiers by diet or supplements a potentially fruitful approach?

• With current scientific knowledge, is it possible to achieve a 10 –15 percent enhancement of soldier performance in certain combat situations through the use of rations and/or nutrients?

• Which food components are the best candidates to enhance military physical and mental performance?

• What is the best way for soldiers to be supplemented—through fortified foods, special foods or beverages, or “vitamin pills?”

• Are there ethical issues that need to be considered with this type of research?

• What regulatory issues must be considered with the types of food components being evaluated by the Army?

There is a large volume of scientific literature on the topic of performance enhancement, but it is of diverse quality. The Committee reviewed the state of knowledge in this disparate area through convening a workshop that was held at the National Academy of Sciences in Washington D.C. on November 16–17, 1992. Prior to the workshop the CMNR asked the Army to develop several scenarios that illustrated the hypothetical application of food components in rations. The workshop included invited presentations from individuals familiar with or having expertise in cognition, endocrinology, exercise physiology, food science and engineering, immunology, metabolism, neuropsychology, nutrition, nutritional biochemistry, performance psychology, and sports medicine.

The Committee's report, Food Components to Enhance Performance (Marriott, 1994), provides responses to the six questions the CMNR was asked to address and includes recommendations for future research. The report also includes the 21 invited papers presented at the workshop. The Committee

formulated its conclusions and recommendations on the basis of the workshop presentations and subsequent discussions and by its deliberations in executive session.

The Committee recommended that the military ensure that troops are fed and hydrated adequately prior to military operations. The CMNR stated that prior to deployment, troops are presumably in good physical condition and have been consuming adequate rations to meet their nutrient needs; therefore, vitamin and mineral supplements are unlikely to improve performance. Stimulants such as caffeine given during continuous operations may help to overcome the effects of physical and mental fatigue. However, the Committee believes that the Army Science and Technology Objective (STO) (Army Science Board, 1991) of a 10–15 percent enhancement in performance of its well-fed, physically-fit soldiers by fiscal year 1998 can be obtained through consumption of specific rations or nutrients is overly optimistic. The CMNR believes there might be opportunities to meet this objective only if enhanced performance is defined as preventing or restoring all or part of the decrease in performance that is usually encountered overextended field operations (since troops in such circumstances tend to reduce food intake, lose weight, and sometimes dehydrate).

The Committee concluded that sufficient evidence exists to conclude that carbohydrates, caffeine, tyrosine, and choline have the potential to sustain performance in militarily relevant situations. The Committee stated that carnitine and structured lipids were food components of theoretical importance but currently offer a low probability of demonstrating improved performance under anticipated conditions in military operations. The following represents a summary of the CMNR recommendations:

Carbohydrates This macronutrient is a fuel source for extended physical activity. Carbohydrate supplements are most useful for persons engaged in continuous, moderate physical activity over at least 1.5 to 2 hours, as it can extend the time to exhaustion. Carbohydrates may also affect behaviors such as mood, performance, and satiety. Research in evaluating the benefits of supplemental carbohydrates on performance should include evaluations of their effects on motivation to operate under stressful conditions such as combat and on coping under such conditions. Laboratory studies indicate that consumption of supplements with a high ratio of carbohydrate to protein increase fatigue. Based on these results, the CMNR suggests that research on sleep promotion could address the macronutrient ratio in supplements.

Caffeine Caffeine affects the central nervous system by blocking adenosine receptors, which tend to delay sleep and reduce the deterioration of performance associated with fatigue and boredom. The principal side effects include nervousness, jitteryness, and decreased sleepiness which may persist for several hours. Caffeine should definitely be considered in developing performance-enhancing rations or ration components. Doses of 300–600 mg/70-kg person will achieve the desired stimulus in those nonhabituated to caffeine. Research is required to determine the effective dosage for those with higher habitual caffeine intakes.

Tyrosine Under highly stressful conditions, this amino acid, the precursor of dopamine, norepinephrine, and epinephrine, may be the limiting substrate for the synthesis of these neurotransmitters. Tyrosine supplements have reduced the adverse effects of hypoxia, cold, body negative pressure, and psychological stress both in humans and animals. Additional research is needed on tyrosine to demonstrate the generalizability of its effects across a wider range of stressors, establish a dose-response function for its beneficial effects, determine whether it is helpful in chronic stress paradigms, determine the safety of its administration, assess the risks and benefits of acute versus chronic administration, and determine the most appropriate method for providing it as a supplement.

Choline Choline has a variety of functions in the body, but its best-known function is as a component of the neurotransmitter acetylcholine. There is evidence that diets low in choline reduce muscle performance. Choline supplements enhance memory in humans; in animals (particularly aged ones), choline supplements enhance memory as well as reaction time. Choline is a normal constituent of many foods and is safe at high levels of intake, so the CMNR recommends that it is worth evaluating to determine whether it may enhance the physical or cognitive performance of soldiers functioning in stressful environments.

Given that the cognitive, emotional, and physical aspects of performance is of crucial importance to all service branches, the Committee further recommended that the military establish an interservice committee to coordinate and facilitate research and development activities in this area. Some of the necessary animal research might be accomplished through the Army-funded neuroscience research at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, to complement and support the human studies at USARIEM.

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The full conclusions and recommendations from this report are included in Appendix I.