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

At the request of the U.S. Army Research Institute of Environmental Medicine (USARIEM), the Committee on Military Nutrition Research met in Washington, D.C. on March 15–17, 1993 to assist the Army in reviewing and evaluating the results of a nutritional intervention project conducted during the training program for the U.S. Army Ranger Class of November, 1992 (Ranger II). This activity was a followup to the Committee's review and evaluation of the results of the Army 's study of the Ranger Training Class of November, 1991 (Ranger I) (IOM, 1992). The CMNR was asked to review the results of this nutritional intervention study conducted by USARIEM, answer five specific questions, evaluate the nutritional health and well-being of Ranger trainees, and make recommendations for future research. For this project, the Committee invited a special consultant to increase its expertise in the areas of energy metabolism and clinical medicine.

The Ranger Nutritional Intervention Study evaluated the health and performance of Ranger trainees under conditions of exposure to caloric and sleep deprivation with intensive physical activity. The Committee 's three-day meeting culminated in the production of the report, Review of the Results of Nutritional Intervention, Ranger Training Class 11/92 (Ranger II) (Marriott, 1993). On the first day, the Committee heard presentations on the research

results of the Ranger study. It met in executive sessions on days two and three to review the research results and develop its recommendations.

The Committee reviewed the Ranger assessment data provided by the Army scientists and the material covered during the oral presentations. A summary of the CMNR responses to the five questions posed by USARIEM are provided here.

1. Was the nutrition intervention (increasing energy provision by 10-15 percent) effective in decreasing medical risk?

   There were several variations in the Ranger II study compared to Ranger I, but the significant intervention variable was the increase of approximately 15 percent in calories, along with additional protein. This change in intake appeared to reduce the severity of the weight loss of the groups and reduced the extremes of weight loss seen in the Ranger I study. A slightly reduced stress on immune function was also noted.

2. Should an even greater increase in energy intake be recommended (assuming it is consistent with Ranger training goals)?

   Overall, the caloric supplement appeared compatible with Ranger goals. However, the value of additional increases in energy intake requires further study.

3. Should any specific supplementation of vitamins, minerals, or protein be considered?

   No. Except for zinc, the data do not suggest any problems with regard to vitamin or mineral nutriture. (It was a rare, unusual, and unexplained finding that average plasma zinc concentrations were elevated in the trainees.) The more hypocaloric the state of the individual, the more protein will be required to minimize negative nitrogen balance.

4. Are the immunological changes noted related to the plane of nutrition during Ranger training or to other (e.g., sleep deprivation) stressors?

   Some are clearly caused by the decreased plane of nutrition. Other concomitant stressors (e.g., loss of sleep and minor infections) could also contribute to the observed immune system derangements.

5. Are the decrements in cognitive function a cause for concern?

   On the basis of data collected during a single study, it is premature to draw definitive conclusions. Answering this question requires full consideration of the nature of activities in which the trainees are engaged.

The Committee divided recommendations for further research into three components: general research issues, questions that can be answered through further analyses of the existing data, and questions that can be answered by additional studies. Among the recommendations are the following:

General The Ranger studies offer the opportunity to collect invaluable information that is of health benefit to both the Army and the civilian population. Continue research with the Ranger Training Classes, particularly under varying environmental conditions. Refine the data analyses so that consideration of data on an individual subject basis is emphasized.

Additional analyses of the Ranger I and II data Investigate adequacy of protein intake, particularly during field training exercises. Determine possible correlations between initial body composition and the outcome physiological variables measured in the studies. Evaluate the composition of the weight regained and the length of time to restore lean body mass following the training program. Determine the cause of the hyperzincemia noted during the training.

Future studies Conduct a future study of U.S. Ranger Training that begins in winter. Develop a protocol to more completely assess recovery from Ranger Training. After training, continue studying a small number of people with the most weight loss; perhaps this project could be conducted in a metabolic unit and include muscle biopsies as well as indirect calorimetry to gain additional data during the recovery phase. Conduct additional immunological studies in the recovery stage. Include, in a future followup study, additional increments of calorie intake and/or sleep to evaluate the degree of the intensity of training necessary to achieve the desired outcome. Establish a procedure for evaluating individual participants longitudinally.

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