Nutritional Needs in Cold and in High-Altitude Environments
Military operations are frequently conducted in locations where soldiers are exposed to desert, arctic, and high-altitude environmental extremes. The success of such operations will be influenced by how well humans can perform in these extreme conditions. Gradual adaptation to these environments aids physiological acclimatization. However, military missions rarely can be planned to allow lengthy acclimatization periods. The recent peace-keeping operation in Bosnia is an example of an operation conducted under adverse conditions with little time initially for preparation or acclimatization. Regardless of climatic conditions, troops must be supplied with food, weapons, housing, and other support facilities that will enable the immediate performance of their mission.
Previously, the Committee on Military Nutrition Research (CMNR) was requested by the U.S. Army Research Institute of Environmental Medicine (USARIEM) to provide reviews and recommendations on nutritional needs of soldiers in environmental extremes, such as the parallel review of the previous CMNR report on nutritional needs in hot climates (IOM, 1993a). In 1993, the CMNR was asked by USARIEM to review research pertaining to nutrient requirements for working in cold and in high-altitude terrestrial environments. While there are differences in the stresses imposed by cold as compared to high-altitude environments, there are enough similarities to make them suitable to address concurrently. In addition, the committee was asked to address the increased energy demands of such environments, consider whether these environments elicit an increased requirement for other specific nutrients, interpret these diverse data in terms of military applications, and make recommendations regarding the application of this information to military operational rations.
Committee members decided that the best way to review the state of knowledge in this diverse area was through a small workshop at which knowledgeable researchers could review published research and provide an update on current
knowledge, and a subgroup of the CMNR met in August 1993 to identify the key topics for review and the speakers with expertise in these topics. The workshop was convened on January 31 to February 1, 1994 and included presentations from individuals familiar with or having expertise in cold and in high-altitude topics, as well as from military commanders familiar with working and training personnel in these environments. Speakers were asked to provide reviews of their area of expertise, which in turn assisted the committee in responding to a series of 15 questions, which have been summarized into the following two overriding questions:
- Aside from increased energy demands, do cold or high-altitude environments elicit an increased demand or requirement for specific nutrients?
- Can performance be enhanced in cold or high-altitude environments by the provision of increased amounts of specific nutrients?
On the day after the workshop, the CMNR met in executive session to review the issues and draw some tentative conclusions. Committee members subsequently met in a series of working sessions to draft the summary and recommendations. The committee's report, Nutritional Needs in Cold and in High-Altitude Environments, Applications for Military Personnel in Field Operations (IOM, 1996a), was originally released in March 1996 as a preliminary report in response to troop deployment to Bosnia, and in May 1996, the full report, including 22 papers presented at the workshop, was released.
Conclusions
The energy requirement for work both in the cold and at high altitudes is increased. However, the increased requirement is adequately met by the cold weather operational rations currently in use. Energy in these rations is primarily provided in the form of carbohydrate. There is insufficient evidence at this time to support providing an increased amount of any specific nutrient in the cold or at high altitudes beyond that already provided in current operational rations.
Additionally, the CMNR emphasizes the critical importance of water discipline, availability of safe fluids for drinking, and a clear understanding on the part of all troops involved in operations or training in cold and in high-altitude environments of the importance of maintaining fluid intake. An impressive body of evidence has already been generated to define the nutritional needs of troops required to engage in military operations under environmental conditions of extreme cold and/or high altitudes.
Recommendations and Areas for Future Research
The committee's extensive list of recommendations and areas for future research can be summarized as follows:
To Commanders:
- Ensure adequate ration consumption.
- Provide high-energy, high-carbohydrate rations. When necessary, adjust rations to provide up to 40 percent of their calories in the form of calorie-dense fat to ensure an adequate supply of food energy in a form that can be quickly consumed.
- Enforce the adequate consumption of fluids through training similar to hot climates.
- Redeploy only those who have regained body mass or weight lost in prior field operations. Provide education regarding the physiological changes and symptoms of altitude-related illnesses.
To Researchers:
- Investigate the potential benefits of supplemental antioxidants, for example vitamin E, in preventing the oxidative damage that may result from work at high altitudes.
- Determine the optimum intake of micronutrients and whether micronutrient supplements will improve performance.
- Evaluate the effect of providing diet-related pharmaceutical compounds, such as caffeine and tyrosine, on the decline in cognitive function that accompanies exposure to adverse environmental conditions.
Additionally, the committee believes that the military services, through volunteer participation in studies and surveys, offer an excellent and often unique opportunity to generate research data and statistics on the nutrition, health, and well-being of service personnel. It is important that future studies include men and women representative of the fall range of ages in the active duty military. These findings can be directly applied to improve both the health of military personnel and that of the general U.S. population.
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The full conclusions and recommendations from this report are included in Appendix F.
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