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1 Introduction The U.S. Army Health Risk Appraisal group surveyed 400,000 active duty U.S. Army personnel in the late 1990s to determine whether or not those personnel met the dietary objectives of Healthy People 2000 (HP2000), a national agenda for health promotion and disease prevention. As reported by Yore et al. (2000), Army personnel generally did not meet the HP2000 goals for nutrition even though sig- nificant progress had been made during 19911998. Although the specific aspects of diet that would be relevant to this Committee on Mineral Requirements for Cognitive and Physical Performance of Military Personnel are lacking, the find- ings from this survey suggest that there are dietary problems in the military popu- lation. The potential for adverse effects of marginal mineral deficiencies among soldiers engaged in training or military operations and the prospect of improving military performance through mineral intakes have spurred the military's interest in this area of nutrition. This chapter discusses some background information on the current knowledge regarding soldiers' eating behaviors, mineral intakes as well as on the physical and mental stress caused by the environmental circumstances (i.e. physical and mental stress) of military garrison training. THE COMMITTEE'S TASK Study Objective The study's objective is to review essential minerals and their potential effects--whether direct or indirect (by preventing diseases)--on military perfor- mance, including neuropsychological and physical performance. In addition, the role of minerals in preventing acute health issues, such as diarrheal diseases and 13
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14 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL infections that could affect performance, is reviewed, and possible prophylactic benefits are summarized. The role of zinc is of particular interest. In addition to zinc, the study specifically identifies the minerals of most importance for mili- tary physical and cognitive performance and evaluates if there is the potential for significant mineral deficiencies in specific military situations, which are outlined in the following section, Specific Questions to be Addressed. The study also assesses the adequacy of current mineral levels in operational rations and recom- mends new levels when appropriate. The mechanisms of action and physiologi- cal effects of interactions, including neural pathway interactions, are considered. Finally, the committee recommends delivery vehicles for adequate mineral lev- els and identifies research needs of military importance. Specific Questions to Be Addressed The committee task addressed the following seven questions: 1. Which dietary minerals are likely to have an impact on human perfor- mance? Are these minerals provided in adequate amounts in the meals, ready-to- eat (MREs) and the current first strike rations (FSRs)? 2. Is there a potential for any significant deficiency in essential minerals when soldiers subsist on (a) MREs during garrison training (i.e., intense training and one-day missions) or (b) FSRs during combat missions (i.e., repeated cycles of three- to seven-day combat missions, with one- to three-day recovery periods that include garrison dining)? 3. During garrison training, do weight loss diets (energy or macronutrient restricted) have the potential to lead to deficiencies of specific essential minerals? 4. Do the high-performance activities of soldiers cause excessive mineral loss, thereby raising the mineral dietary requirements? 5. Is there any scientific evidence that mineral supplements (individually or in combination) improve soldiers' performance? 6. Are the Military Dietary Reference Intake (MDRIs) for dietary minerals reflective of the Institute of Medicine (IOM) Dietary Reference Intakes [Recom- mended Dietary Allowance (RDA) or Adequate Intake (AI)]? Should the MDRIs follow the RDAs or AIs or should differences persist because of soldiers' spe- cific needs? 7. How do changes in the drinking water sources used during military deployment (e.g., U.S. public water supply versus bottled water versus field- purified water) affect the balance of essential dietary minerals? ORGANIZATION OF THE REPORT This report is organized into an executive summary, five chapters, and seven appendixes. The chapters include an introductory chapter and subsequent chap-
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INTRODUCTION 15 ters that answer the seven questions comprising the committee task. Appendix B is composed of the workshop speakers' written presentations; although the pre- sentations formed the basis for the committee's answers to the military's ques- tions, they should not be construed as representing the committee's views. Chapter 1 provides background information on the current knowledge re- garding soldiers' eating behaviors as well as on the physical and mental stress caused by military garrison training or operations. Chapter 1 also offers facts on the mineral content of rations and its intake by military personnel and addresses the potential effects of nutrient deficiencies due to inadequate intake or higher requirements during military operations. Chapter 2 provides information and recommendations on the development and uses of MDRIs and a description of strategies to increase intake of specific minerals, whether via usual foods, fortifi- cation, or supplementation. Chapter 3 features a description of the metabolism and needs for selected minerals by military personnel under garrison training, recommendations on mineral intake levels, and an assessment of mineral level adequacy in operational rations. Chapter 4 includes a prioritization of the re- search needed to answer information gaps and details of study designs required to gain such information. Chapter 5 presents a summary of some of the commit- tee's findings by answering to the specific questions posed to the committee. Appendix A presents the workshop agenda, and Appendix B features the workshop presentations organized by topic, including an introduction to infor- mation about combat rations; mineral metabolism; and the role of minerals in sustaining and improving physical and mental performance. Appendix C con- tains summary tables of nutrient recommendations for assault rations and of mineral levels in operational and restricted rations. The biographical sketches of the speakers and of the committee members are presented in Appendixes D and E, respectively. Appendix F lists acronyms and abbreviations, and finally, Ap- pendix G provides a glossary. ENERGY EXPENDITURE AND FOOD CONSUMPTION DURING MILITARY OPERATIONS OR TRAINING As mentioned previously, this task is concerned with soldiers mainly during garrison training. Although the unique features of high-intensity operations are not the focus of this task, they are summarized so that comments on the mineral levels in IOM (2006) are put into context. The committee has defined garrison training as situations during which soldiers spend the day performing a military mission or training exercises while living in a military base; sustained operations are defined, as in a previous IOM report (2006), as repetitive three- to seven-day high-stress missions interspersed with restorative periods of one to three days. Unfortunately, data on energy expenditure and intake and on food consumption by soldiers in the field are scarce and mostly anecdotal. The committee received no information regarding soldiers' energy expenditures performing the typical
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16 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL training activities addressed in this report during deployments or when the sol- diers participate in one-day missions, or both. In the absence of actual data, estimated energy expenditure can be assumed from published literature that mea- sured energy expenditures during similar military activities, albeit performed during training at home or abroad, when in noncombat situations. Fortunately, there have been a number of such studies that have been reviewed recently by Tharion et al. (2005). Because the recent report Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations includes a detailed descrip- tion on soldiers' energy expenditure and food habits during sustained operations (IOM, 2006), this section instead will describe soldiers' expenditures during garrison training, the second scenario under consideration for this report. The reader is referred to IOM (2006), Nutrient Composition of Rations for Short- Term, High-Intensity Combat Operations for further description on energy ex- penditure and intake and on food consumption during sustained operations. The wide range in total energy expenditures of various military groups and the factors that appear to contribute to the related differences have been de- scribed previously (Tharion et al., 2005). Field studies suggest that the typical energy intake of military personnel (soldiers, sailors, airmen, and marines) under a variety of scenarios and climatic conditions is approximately 2,400 kcal/day, even though energy expenditures of soldiers in combat units range from approxi- mately 4,000 to 7,131 kcal/day depending on the level of physical activity and on the environment. Interestingly, these reports note that measured energy defi- cits for soldiers (whether in training school or in combat) were significant (Tharion et al., 2005). However, a number of these studies were conducted with soldiers in combat operations that involved an extreme level of physical exer- cise; the committee does not include these combat operations in its definition of garrison training. After these extremely demanding combat situations were ex- cluded and support activities of moderate activity level were included, energy expenditures of male soldiers in garrison training varied from 3,500 (e.g., sup- port combat soldiers involved in moderate exercise) to 4,500 kcal/day (e.g., Ranger training under intense exercise). For female soldiers, energy expendi- tures varied from 2,300 kcal/day while undergoing basic training to 3,000 kcal/ day while running medical operations in the field. The committee assumed that the energy expenditures while in garrison training will be an average of 4,000 and 2,500 kcal/day for men and women, respectively. Conversely, for male sol- diers in sustained operations (repetitive three- to seven-day missions in locations off of the military base, with rest periods of one to three days), the committee assumed an average energy expenditure of 4,500 kcal/day (IOM, 2006). During garrison training or one-day missions in the field, soldiers typically have free access in dining facilities to cafeteria-style food for breakfast and dinner and have field rations (MREs) during the day. For these situations, and because there is access to the cafeteria-style food at least twice a day, the com- mittee assumed that soldiers were in energy balance. In contrast, during the
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INTRODUCTION 17 unique circumstances of sustained operations, soldiers' energy balance is nega- tive, as suggested by data collected during intense combat training. Negative energy balance could be detrimental to health and performance if an adequate diet were not consumed or if the operation were too prolonged, or both. Such data indicate that with high-energy expenditures of 4,000 kcal/day or more, sol- diers tend to consume an average of 3,000 kcal/day, and even less when they depend on operational rations (i.e., rations designed for a wide variety of opera- tions and settings but consumed for a limited period of time, for example, MREs). In addition to the potential performance decrements due to a variety of stressors during short-term missions, underconsumption may result in a set of conse- quences ranging from body protein loss and fatigue to deficits in essential micro- nutrients; all of those consequences may impair physiologic functions and result in performance decrements. The adverse effects of stress combined with food underconsumption are of concern and have been the subject of a number of IOM reports. Although stress during combat operations is unavoidable, much can be done to improve soldiers' nutritional status. MINERAL CONTENT OF MILITARY RATIONS The mineral content of military rations has been estimated as described by Baker-Fulco (2005; see Appendix B). The data presented are derived from a variety of sources; calculations of the estimated contents vary and are based not only on actual food analysis data but also on food composition data and on the reports by the food companies manufacturing the food items. As the author points out, multiple uncertainties translate into final estimated values that either are underestimated or overestimated depending on the calculations made. Nev- ertheless, the estimated values represent the best available data. Another short- coming is that analytical data do not exist for some nutrients, for example, copper. The mineral content of food items can be used to evaluate soldiers' mineral intake (see the following section, Mineral Intake of Military Personnel), and it also can be used as a benchmark for the continued improvement of rations. Tables in Appendix C show the variability in mineral content of menus to be significant and reflect the diverse nature of the individual food items included in each menu, which is necessary to ensure the menus' acceptability. MINERAL INTAKE OF MILITARY PERSONNEL Food Intake Since the military began its continued improvement of food and rations for military personnel, there have been some studies that have examined food intake behavior and its impact on soldiers' performance and health. The military also has studied the influence of different environments (e.g., cold, high-altitude cli-
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18 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL mates or hot, desert-type climates) on soldiers' nutrient requirements and eating behavior. Johnson and Sauberlich (1982) conducted a literature review on the prolonged use of operational rations and found that as early as 1966 research indicated that more nutrient-related studies were required. For example, Consolazio's (Consolazio et al., 1966) study examined energy requirements at high altitudes and concluded that for optimal military performance and energy an evaluation of nutrient requirements, including micronutrients, was necessary to improve military rations. This conclusion was reached after blood and serum tests revealed some potential nutrient inadequacies. Later, a series of laboratory metabolic studies indicated similar conclusions regarding the need for adequate levels of minerals to maintain health (Consolazio et al., 1967). Although some studies have measured the suitability of using MREs (Edwards et al., 1991), only a few studies performed with military personnel have included mineral intake in their designs. In these cases, a comparison between the intake and the MDRIs for minerals is made (see Table 1-1 for current MDRIs for minerals). For example, the health status of 15 soldiers of average physical fitness was studied when they were eating MREs ad libitum during 12 days at 7,200 feet of altitude (Askew et al., 1986). Exercise was strenuous during 7 of the 10 of the days in the field, and a decrease in the soldiers' maximal aerobic capacity of 5 percent was reported. Caloric intake was 67 percent of energy expenditure. The mean iron intake during the study was 14 mg/day (MDRI = 10 mg/day for men [U.S. Departments of the Army, Navy, and Air Force, 2001]). Calcium and magnesium intake was 567 and 245 mg/day, respectively (MDRI = 1,000 mg/day; MDRI for magnesium = 420 mg/day for men [U.S. Departments of the Army, Navy, and Air Force, 2001]). No other essential mineral was measured. The authors concluded that the level of performance was reasonable but recom- mended supplementation with a carbohydrate source for energy. A more recent study was conducted on the physiological and psychological effects of eating foods from three different menus during 12 days of military training in a tropical environment (Booth et al., 2003). Three groups of Austra- lian Air Field Defense Guards received either freshly prepared foods or one combat ration pack (CRP) or half of a CRP. Substantial underconsumption re- sulted in slight weight loss, protein catabolism, and immune suppression in the groups eating rations; members of those two groups also reported greater fatigue than members of the group that ate fresh foods. Under these conditions de- creased serum ferritin levels (a measure of iron status) and dehydration were observed when consuming either of the rations or the freshly prepared foods (Booth et al., 2003), possibly due to overall underconsumption. However, direct association between decreased serum ferritin and performance could not be made from this study. Other studies have attempted to investigate the effect of micro- nutrient supplementation on military performance; one of them showed that for healthy adults, vitamin and mineral supplement consumption for three months did not improve military physical performance (Montain and Young, 2003).
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INTRODUCTION 19 One of the military's main interests has been zinc supplementation, espe- cially because of the potentially marginal intake of soldiers as compared to recommended requirements, difficulties in assessing zinc status, and questions regarding the body's redistribution of zinc when under stress. A lack of perfor- mance response when supplementing with zinc has been reported in two studies (Singh et al., 1994, 1999); however, in both of these studies the intake of zinc by nonsupplemented control groups was adequate. The question remains whether zinc might have beneficial effects as a supplement when dietary intake in food is compromised. Tharion et al. (2004) evaluated the adequacy of the food-service food pro- vided to Special Forces soldiers in garrison training. Among the data collected were the following mineral intake levels based on the food items consumed (as reported by the participants): · Calcium, 1,065 mg (9521,236 mg), (MDRI = 1,000 mg for men [U.S. Departments of the Army, Navy, and Air Force, 2001]); · Copper, 1.7 mg (1.52.1 mg), (no set MDRI for copper, IOM RDA = 0.9 mg for men >19 years of age [IOM, 2001]); · Iron, 19.3 mg (16.622.9 mg), (MDRI = 10 for men [U.S. Departments of the Army, Navy, and Air Force, 2001]); · Magnesium, 341 mg (306409 mg), (MDRI = 420 for men [U.S. Depart- ments of the Army, Navy, and Air Force, 2001 ]); and · Zinc, 16.3 mg (14.120.7 mg), (MDRI = 15 for men [U.S. Departments of the Army, Navy, and Air Force, 2001]). The study also reported the amount of food and nutrients that was eaten on weekdays and weekends. The large variations were associated with more food eaten outside the cafeteria on the weekends. These results are less relevant for the current task because the soldiers were eating cafeteria food at all times and not food from rations. However, the results do show that even when having free access to food, the intake of some minerals was low. For example, only about 40 percent of the subjects achieved the dietary goal for magnesium (MDRI = 420 mg for men [U.S. Departments of the Army, Navy, and Air Force, 2001]). A more relevant study by Thomas et al. (1995) assessed the nutritional intake of soldiers in a field environment during 30 days when the soldiers were provided either three MREs or two test rations and one MRE (standard field ration menu). The group with three MREs ate less and had mineral intake levels lower than the group eating the test ration; those intakes were also lower than the MDRI for calcium (868 versus 1,000 mg), zinc (9.3 versus 15 mg), and magne- sium (306 versus 420 mg). The intake of zinc was notably low. Measurements of iron status (serum levels and ferritin) were within normal levels. Serum levels for the other minerals also were normal. Serum zinc was not measured. Perfor- mance, measured by road march times, was not altered by the two diets. General
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20 1930 Dietary Ration RE Minimum b µg 50 35% Women 200 3 8 0.6 0.7 8 0.7 1.2 500 45 40 200 ND ND ND 500 ND ND Restricted Daily Intake NS 1,500 Military to and b Men Intake RE Operational Daily Compared µg Rations, 91 35% 5 1.2 1.3 1.3 2.4 NSOR, Ration, Minimum NS 3,600 494 90 15 80 16 400 ND ND ND ND ND 1,000 1,000 f Population RE Restricted omen 5093 D 5 1.1 1.1 1.3 2.4 ND N 800 75 15 65 14 400 ND ND ND ND ND and W 2,300 1,000 General f Population the b RE 63119 D 5 1.2 1.3 1.3 2.4 90 15 80 16 D for ND N 400 ND N ND ND ND Military MDRI Men 3,250 1,000 Operational, 1,000 Intakes d g Feeding, e omen 46 2035% a 130 700 5 1.1 1.1 1.3 2.4 75 15 90 14 30 25 400 425 900 W 2,3502,400 1,000 Garrison AMDR Recommended in c or g Population AI, RAE e 56 2035% Dietary 130 5 1.2 1.3 1.3 2.4 55 900 90 15 16 30 35 120 400 550 900 Personnel General RDA, Men 3,1003,150 1,000 for Daily Intakes Current (mg) (kcal) (g) 1-1 Age Energy (µg) (µg) (mg) (mg) Acid kcal) (mg) (µg) (mg) (µg) NE) (µg) 6 DFE) 12 of or Intake (g) A C D E K (mg) B of (mg (µg B (µg) (mg) (mg) (µg) (% TABLE Recommended Years Nutrient Sex Energy Protein Fat Carbohydrate Vitamin Vitamin Vitamin Vitamin Vitamin Thiamin Riboflavin Niacin Vitamin Folate Vitamin Biotin Pantothenic Choline Calcium Chromium Copper
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21 and body using: Activity Reference using: older respectively weight. 2 8 2.0 2.53.5 8 Retinol respectively and age 75 28 210 ND ND 350 Dietary = older of body weight. age and RAE of years g/kg body 19 years Military = years 19 .80 years /kgg of. Rations; 19 ages 19 and 1.5 MDRI 30 to men and 0.8 for 30 women 4 15 3.2 5.07.0 55 15 of for depicts 150 420 ND ND 700 Operational of depicts Equivalents; For equation range recommendations equation (3.23.9) range Folate active; intake 3.1 15 2.5 3.6 55 12 Standards = 150 320 ND ND 700 active; Dietary requirement = level protein recommendations = requirement and level intake DFE Nutritional energy = energy activity 4 10 3.2 55 15 150 420 ND ND (4.55.5) 700 activity women) protein 5 Ranges; NSOR for estimated physical and estimated kg physical 57 2.3) equivalents. women) ( Distribution Specified; Medicine military); and Medicine Not of as for men 3 18 1.8 4.7 1.5 8 = retinol military); of kg 45 55 = as 150 310 700 for NS (same 62 RE kg Institute m (2001). (same Institute and Macronutrient (70 m using =1.63 men 2.3) Force using ( 1.75 for Equivalents; Allowance; Air = weights height kg 4 8 2.3 4.7 1.5 45 55 11 Acceptable and 150 400 700 = body (79 Niacin = Dietary expenditure, height expenditure, Navy, AMDR NE noted. reference kcal. weights energy kg; energy 50 reference Army, = reference kcal. = 57 body Intake, otherwise the kg; 50 = Recommended 70 nearest Determined; = of intake inake Medicine (µg) = unless nearest weight the of reference (mg) to (mg) (mg) Not (g) (mg) (µg) (µg) Adequate = = RDA energy the energy weight (g) to AI ND Institute military (mg) (mg) (2004a) Departments reference (2002/2005). rounding IOM U.S. Fluoride Iodine Iron Magnesium Manganese Molybdenum Phosphorus Potassium Selenium Sodium Zinc NOTE: Intake; equivalents; assuming assuming using IOM a b c reference rounding d body and e f using g
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22 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL health (constipation, diarrhea, hunger, and thirst) and mood (alertness, relax- ation, confusion, and sleepiness) status were assessed by questionnaires. As with physical performance, no differences were observed with the two diets. How- ever, the authors of this report postulated that if calcium and iron intake for male soldiers is just above the military standards, inadequate intake of these minerals by female soldiers would be likely because of their higher requirements. Thus, female soldiers could be at risk of iron and calcium deficiencies that might result in health or performance decrements. Gender differences regarding energy and nutrient intake were examined dur- ing an 11-day field training exercise; the objective of the study was to determine if the standard MREs were adequate to meet women's nutritional needs (Baker- Fulco et al., 2002). The energy intake of the female population was lower than that of the male population among the combat-support hospital personnel studies (mean intake of 1,818 kcal/day versus 2,427 kcal/day). Likewise, a larger pro- portion of women did not meet the intake standards for several nutrients, includ- ing calcium, iron, magnesium, and zinc. However, when body weight was ac- counted for, those gender differences were mostly eliminated. More than half of the women's intake for calcium, zinc, and magnesium was inadequate if the Estimated Average Requirements (EARs) were used as reference values for group adequacy. Approximately 10 percent of the women did not meet the EAR for iron. This study also revealed an interesting observation--a significant amount of energy and nutrient sources derived from nonration foods; for ex- ample, about 7 percent of the women obtained more than 20 percent of their calories from nonration foods. The results agree with an earlier study that exam- ined the health, performance, and nutritional status of U.S. Army women during training at Fort Jackson, South Carolina, for seven consecutive days (King et al., 1994). The meals consisted of three A-rations each day. Once again, the authors concluded that intake of calcium, magnesium, iron, and zinc was less than the MDRI. Low mineral intake also was noted in a study that evaluated consumption, acceptability, and performance outcomes for an experimental ration (the T-ration) consumed for 60 days as compared to a B-ration (canned, dehydrated, and dried ingredients) (Tharion et al., 2000). Intake of energy, folate, magne- sium, zinc, carbohydrate, and fiber was lower than recommended for the T- ration group; however, there were no notable decrements in physical perfor- mance (i.e., construction-type work) or mood. Another study that tested the use of a supplemental carbohydrate beverage to meet the nutritional needs of soldiers (n = 63) under intense exercise in the desert, revealed significant inadequacies in calcium, magnesium, and zinc intake (Tharion et al., 1997). It is interesting that the inadequacies were more notable for those who, in addition to receiving the unitized group ration, were supple- mented with carbohydrate; in this supplemented group, 59 (calcium), 34 (mag- nesium), 15 (iron), and 31 (zinc) percent of soldiers did not meet 70 percent of
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INTRODUCTION 23 the recommended MDRI. The authors suggested that when a carbohydrate sup- plement is provided, changes in consumption patterns may compromise the in- take of essential micronutrients. From the few studies described, it can be inferred that the mineral intake of soldiers is compromised, even if marginally in some instances (see Table 1-1 for current MDRIs). Magnesium and zinc appear to be the minerals that are more often consumed at inadequate levels. Studies evaluating nutrient intake ideally would assess women and men separately since their needs and intake differ. In general, as Baker-Fulco concluded (Baker-Fulco, 2005; see Appendix B), the data are insufficient to have a clear picture of all the mineral intake from food. Information on nutrient intake when eating food from the dining facilities or when eating food from rations would help in designing food items with a more adequate nutrient density, especially for women; this is ultimately necessary in order to ensure that the military requirements for nutrients are met by most military personnel, both men and women. To calculate nutrient intake accu- rately, better data on nutrient composition of food items need to be collected. Supplement Intake If data on mineral intake from foods are scarce, as the evidence in the previ- ous section suggests, then, data on the intake of supplements by military person- nel are even less abundant. Recent personal communications by U.S. Army Re- search Institute of Environmental Medicine (USARIEM) officials confirm that information on dietary supplement intake by soldiers is scarce (personal commu- nication, K. Friedl, USARIEM, June 13, 2005). Nevertheless, it is a fact that soldiers have access to and readily use dietary supplements, especially weight loss supplements, protein supplements, creatine, and energy drinks. Although anecdotal data suggest that soldiers also might take calcium supplements, there are no published data either to confirm or refute that statement. The extent of dietary supplement and vitamin and mineral intake levels obtained via supple- mentation are unknown. There is, however, one relatively recent study that addresses the intake of dietary supplements by U.S. Army Special Operations candidates (Arsenault and Kennedy, 1999). To collect the data, the authors administered 2,215 surveys to males entering the U.S. Army Special Forces and Ranger training schools. The results show that about 85 percent of men were using or had used dietary supple- ments in the past and that 35 percent were using them daily. These findings suggest that use among military personnel might be much higher than that by the general U.S. population (about 45 percent of the U.S. population reports using dietary supplements [Radimer, 2003]), possibly because of soldiers' concerns over the importance of adequate nutrition and health status for military training. For example, studies on supplement consumption by athletes, a population that might better resemble the military personnel than the general population, find
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INTRODUCTION 25 In other situations, such as garrison training, underconsumption does not appear to be of concern, according to military sources. In these cases, soldiers eat mainly at dining facilities and follow a more normal eating schedule; nega- tive energy balance and weight loss seemingly do not occur. Although during garrison training the physiological consequences are not so well described, the stress endured still could be detrimental to the immune and endocrine responses and contribute to dehydration, kidney stone formation, and gastrointestinal dis- turbances (Montain, 2006; Montain and Young, 2003). Consequences on Physical and Cognitive Performance As described by Montain (2006), performance of simple and well-learned motor tasks (e.g., weapon handling) does not appear to be compromised by sustained operational stress (Haslam, 1982). Endurance time, however, is im- paired frequently during aerobic exercise tasks (VanHelder and Radomski, 1989), and there is a higher perception among subjects of an increased effort needed to perform the same task. Nindl et al. (2002) reported a 25 percent lower level of work productivity from test group subjects, as compared to control group sub- jects, on a physical persistence task (building a wall for 25 minutes) after test group subjects were fed a hypocaloric diet (caloric content of diet was at least 50 percent less in kilocalories than the soldiers' energy expenditures) and allowed to sleep for only 1 h/day over a four-day period. This is consistent with the hypothesis that sustained operations compromise performance when tasks are prolonged and monotonous. Operational effectiveness also is affected if sleep is inadequate, independent of energy intake (Rognum et al., 1986). Effects of Energy Balance and Nutrient Intake The weight loss observed during sustained operations appears to have incon- sistent effects on soldiers' performance (Montain and Young, 2003); this possibly could be due to several factors--lack of the validity of the physical performance test used in the study design, severity and length of the energy deficit, or other factors related to the study design (e.g., small sample sizes). Earlier, shorter dura- tion studies with minimal lean body mass loss generally showed little or no decre- ment in muscle strength, power, or fatigability (Bulbulian et al., 1996; Guezennec et al., 1994; VanHelder and Radomski, 1989). A study by Booth et al. (2003), concluded that a 3-percent weight loss after 12 days was unlikely to be detrimental to military performance. On the other hand, another study, in which male soldiers were on three different energy intake levels (1,800, 3,200, 4,200 kcal/day) while performing a sustained physical activity for one week, resulted in reduced maxi- mal aerobic power and endurance only when consuming the lowest energy diet (1,800 kcal/day) (Guezennec et al., 1994).
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26 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL Despite the seemingly contradictory results and different study designs, the data available suggest that moderate levels of weight loss (35 percent) have limited ill effects on the ability of soldiers to perform military tasks. The recent IOM report (2006) Nutrient Composition of Rations for Short-Term, High- Intensity Combat Operations, recommends that a hypocaloric ration should be used in a continuous manner during sustained operations (repetitive three- to seven-day missions with one- to three-day resting periods during which dining facilities are available) only if soldiers' weight is maintained within 10 percent of the original weight. The committee recommended that any soldier who loses more than 10 percent of his original weight not be sent to sustained operations again until he regains no less than 5 percent of his original weight. In that same report, the committee concluded that for optimization of mili- tary performance under very short periods of time a ration with the appropriate mixture of macronutrients and micronutrients was more critical than a ration for maximizing energy intake. The available scientific data support the development of a high-protein, high-carbohydrate ration to optimize soldiers' physical and cognitive performance during short-time sustained operations. The committee recommendations, however, were limited by the scarce data available, especially in regard to specific nutrients; nevertheless, the committee recognized that pre- liminary data show promise for some nutrients and dietary supplements. More studies need to be conducted so that rations will continue to improve; it is par- ticularly important that military situations in which stress and intense exercise are a daily constant be emulated in such studies. According to the IOM report (2006), the micronutrients warranting further study are vitamins C and E; the B vitamins; and minerals, including zinc, sele- nium, iron, and copper. Their potential contribution to antioxidant systems, im- mune systems, and physical and cognitive performance is a subject of debate. There is less scientific certainty on the effects of other potential bioactive sub- stances, such as creatine. In addition to nutrient level and energy content, other factors--including time of meal ingestion; content of the previous meal; and psychosomatic factors that affect acceptability of the ration--might influence soldiers' eating behavior and military performance. These additional factors might explain the previously described divergent results on performance effects of eating meals with varying energy intake. Effects of Mineral Status Minerals are essential nutrients, and researchers have observed the signs and symptoms that develop as a result of inadequate status from poor intake or from various diseases. Even when deficiencies are marginal, physical and cognitive functions that are important to military performance might be affected. Although not studied in military situations, adverse outcomes due to profound mineral
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INTRODUCTION 27 deficiencies could include impairment of the immune system, decreased work productivity, increased prevalence of infections, cognitive decrements, and sleep disturbances. There is little known about the potential effects of nutritional or pharmachological interventions with dietary minerals intended either to restore normal mineral status or to enhance the status with the goal of improving a particular function (e.g., the immune responses to infection). As explained by Friedl (2005; see Appendix B), there is no clear and direct evidence that marginal deficiencies among military personnel affect their physi- cal or cognitive performance. The lack of evidence, however, might stem from the fact that many variables have not been taken into account or obscure other effects. For example, as stated previously, dietary intake data are limited and, moreover, data have seldom been collected by gender. Given the different re- quirements and activities of men and women, the absence of data by gender is an impediment when attempting to describe mineral intake and potential effects of deficiencies. Furthermore, the mineral status of "at-risk" populations (e.g., physi- cally active women and their need for iron) has not been evaluated routinely, and therefore, the relationship between mineral status and performance of subgroups within the military cannot be established with a high level of confidence. Many of the field-related activities and scenarios common during military life could have a measurable impact on soldiers' mineral status. For instance, higher-than-normal sweat losses or minerals redistribution among body com- partments due to exercise or stress might increase the need (and therefore re- quirement) for certain minerals. Because numerous studies have linked certain mineral deficiencies with decreased work productivity, higher prevalences of infection, and cognitive decrements in the general population, there is interest in ensuring soldiers' optimal mineral status. Unfortunately, many of the studies on minerals and these outcomes have been conducted with children and often in developing countries where other nutrient deficiencies prevail. Even in studies that are conducted with adults, extrapolation to unique military circumstances is challenging at best. Nevertheless, the idea that mineral status could be an impor- tant factor in maintaining a soldier's performance is an interesting proposition that needs to be explored. One of the studies performed during Ranger training provides some interest- ing results regarding the effect of exercise on mineral status. As indicated by Friedl (2005; see Appendix B), within the first few weeks of the exercise and training course male subjects experienced a decrease in iron status, however, their iron status was corrected by the end of the course. Likewise there were no differences in zinc or copper status between the baseline and the end of the training course. The author explains that periodic re-feeding corrected any defi- ciencies and that the loss of muscle mass in this study would have provided a steady supply of minerals and nutrients into the circulation. Thus, even though the direct link between mineral deficiency and perfor- mance decrements in the military has not been established, enough scientific
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28 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL data derived from studies on the general population are available to suggest that a more in depth analysis of the potential link is warranted (see Appendix B). Furthermore, the limited military data available suggest that dietary intake for some minerals might not be adequate and that mineral status might be compro- mised by the multiple stressors of military activity. Effects of Sleep Deprivation Anecdotal evidence indicates that during garrison training, soldiers generally do not suffer from sleep deprivation. However, as indicated in the IOM report (2006) Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations, surveys conducted in the field during combat missions point to fre- quent instances of sleep deprivation (e.g., some soldiers sleep an average of 4 h/ day; most of them, however, sleep 56 h/day). A recent CMNR report included a review on the consequences of sleep deprivation on military personnel (IOM, 2004b). The efficiency of combatants in sustained operations can be compromised significantly by inadequate sleep (Krueger, 1991). The 2006 IOM report noted that by the end of three days without sleep, combat service members may be consid- ered totally ineffective in the operational setting, especially if they are performing complex tasks such as operating computerized command-and-control centers. Al- though three days of sleep deprivation are rare in scenarios of sustained operations, decreases in cognitive function still may be expected since assault operations pro- vide shortening of sleep time and can last up to a month. Likewise, even though it appears that a major loss of sleep during training is not usual, one can imagine that, at times, unpredictable events can happen during battle and wartime and, conse- quently, sleep deprivation can occur. Critical abilities such as vigilance and atten- tion suffer, reaction time is impaired, mood declines, and some personnel begin to experience perceptual disturbances. Numerous studies have demonstrated that cog- nitive abilities as well as marksmanship are compromised, both of which can have irreversible, adverse consequences. Interestingly, when task durations extend be- yond 15 to 20 minutes, performance deteriorations from fatigue become far more pronounced than when the task durations are shorter (Caldwell and Ramspott, 1998; Wilkinson, 1969; Wilkinson et al., 1966). Despite the fact that not all types of performance are affected to the same degree by sleep loss, fatigue from pro- longed duty periods clearly jeopardizes unit readiness in the operational context. This is especially the case for tasks that are not only lengthy but also boring or devoid of performance feedback. Effects of Stress The stress response consists of two major components--the neuroendocrine arm, or hypothalamic-pituitary-adrenal axis; and the adrenergic arm, comprising the sympathetic nervous system and adrenal medulla. Together these organs and
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INTRODUCTION 29 nerves release a cascade of hormones: hypothalamic corticotropin releasing hor- mone (CRH), pituitary adrenocorticotropin, and adrenal glucocorticoids; and the adrenergic neurotransmitters and hormones (norepinephrine and adrenalin) that jointly constitute the physiological stress response. At the same time as the stress response is activated, the parasympathetic cholinergic mediated responses (such as digestion and gut motility) are generally inhibited (Marques-Deak et al., 2005). Activation of the stress response and inhibition of the cholinergic nervous system set into motion a series of behavioral, physiological, and metabolic re- sponses that prepare the organism to fight or flee. These behavioral changes in- clude focused attention, increased vigilance, and inhibition of appetitive behaviors (including eating and drinking). At the same time, some aspects of the immune response are enhanced, and white blood cells are mobilized from immune organs and carried to injury sites (Viswanathan and Dhabhar, 2005). Although such ef- fects are beneficial in acute stress situations, such as those that occur under assault conditions, long-term chronic stress can be detrimental to health. During chronic stress, immune responses generally are suppressed, or shifted from a TH1 (cellular) pattern to a TH2 (humoral) pattern of immunity. Pro- inflammatory cytokine production is suppressed, and anti-inflammatory cytokine production is enhanced. At a clinical level, chronically stressed individuals show decreased antibody production to vaccination, prolonged wound-healing, and greater severity of viral infection (Cohen et al., 1997; Glaser and Kiecolt-Glaser, 2005). Both acute and chronic stress may affect nutritional status by suppressing appetite, food intake, and digestion and by changing nutrient metabolism. In addition, nutrient metabolism and decreased food and water intake can indirectly alter immune responses and susceptibility and resistance to infection. During chronic stress, the stress response may shift from a primarily CRH-driven stress response to one that is driven by vasopressin and may be, therefore, associated with alterations in thirst, salt preference, and drinking behavior. While the stress hormones and mediators alter appetite and feeding behav- ior, they also alter metabolism. Glucocorticoids increase gluconeogenesis and glucose mobilization, amino acid absorption, and protein metabolism (Barthel and Schmoll, 2003; Elnif et al., 2005; Nzang Nguema et al., 2005). Inhibition of cholinergic systems during acute stress slows gut motility and delays digestion and absorption (Chang et al., 2003). Furthermore, activation of the stress response, and the concomitant release of stress hormones (glucocorticoids) and noradrenergic neurotransmitters and adrenalin, directly affects immune responses; glucocorticoids tend to suppress immunity (Webster et al., 2002), and adrenergic mediators tend to enhance im- munity (Sanders, 2005). In addition, the cholinergic nervous system directly affects inflammation--the activation of the cholinergic pathways is generally anti-inflammatory (Pavlov and Tracey, 2005). The time-course and intensity of stress, whether acute, sub-acute, or repetitive (chronic), affect these outcome
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30 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL measures differently. Acute stress may enhance immunity, particularly delayed- type hypersensitivity (Dhabhar and Viswanathan, 2005). Repetitive stress with- out adequate recovery time between stress episodes (chronic stress) tends to suppress immunity (Glaser and Kiecolt-Glaser, 2005). Also different types of stress--whether physiological (pain, blood loss, dehydration, sleep deprivation) or psychological--may differentially activate neural pathways and different ef- fector arms of the stress response, and thus may differentially affect appetite, thirst and drinking behavior, and immune responses (Li and Sawchenko, 1998). Consequently, in optimizing nutrition in garrison training or combat, these physiological constraints should be taken into account. The decrease in caloric intake and change in drinking behavior and taste that personnel experience in the field may not be voluntary but might be, at least in part, related to activation of the stress response, which is in turn necessary for optimal performance. In this case, attempts to voluntarily increase intake may not be successful. Therefore, rations should be designed taking into account this acute altered physiological status and should not tax the system's coping ability. Such strategies are impor- tant in preventing further compromise, since extreme weight loss in itself may further suppress immune function (IOM, 1999). DEVELOPMENT AND USE OF MILITARY NUTRIENT STANDARDS The U.S. Army's Surgeon General has the responsibility of establishing and overseeing two different types of nutrient standards for military personnel: (1) the MDRI for military feeding and (2) nutritional standards for operational ra- tions (NSORs). The current military standards, as well as the RDAs and AIs for the general population, are shown in Table 1-1. The military standards apply to hospital and other food service programs and to the Department of Defense Combat Feeding Program. The Surgeon General also must identify the effects of environmental factors on energy and nutrient requirements. As scientific information is gathered and new standards for the general population are updated, the Surgeon General is responsible for revising the military nutrition standards and ensuring that nutri- ent composition of the rations and planned menus meet the military standards. The current military nutrient standards (MDRIs and NSORs) were revised in 2001 (U.S. Departments of the Army, Navy, and Air Force, 2001). The standards were based on the recommendations for the U.S. general population as described in various IOM reports (IOM 1997, 2000b; NRC, 1989). The MRDIs are mostly identical to those used for the general population, except for cases in which the idiosyncrasies of the military environment call for different criteria to be consid- ered. For example, working in a hot environment (as is often the case in recent years), results in larger losses of fluids, sodium, and potassium; these situations call for higher intake of those electrolytes, as described in Army Regulation 40-25 (U.S. Departments of the Army, Navy, and Air Force, 2001).
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INTRODUCTION 31 MDRIs are intended for use by nutritional specialists to develop menus and ensure adequate nutrition of military personnel. The use of MDRIs to plan menus for individuals or groups has proven to be a complex exercise; as such, it re- quires the involvement of nutritional experts that are versed in the development of nutrient standards, as well as in the uncertainties and limitations of IOM's nutrient standards. Failure to apply the standards appropriately could result in menus with inadequate nutrient content, and as a result, might lead to adverse consequences, including health and performance decrements. Two IOM reports (IOM, 2000a, 2003) provide advice and examples of appropriate processes to use when planning and assessing menus and rations. The advice in those reports must be applied correctly for the planning and assessment to be appropriate for and beneficial to the military. The NSORs are specifications for the nutrient composition of rations con- sumed by military personnel involved in diverse off-base military activities-- ranging from field training exercises to combat missions. These nutrient speci- fications are designed to maintain health and performance over multiple days of continuous subsistence. In practice, the rations are used in many ways. For example, during one-day training activities, soldiers might have breakfast in the cafeteria, operational rations for lunch at the training site, and dinner again in the cafeteria. However, the primary intended use of operational rations is during combat missions where there is no fixed military facility to provide meal service. The NSOR specifications are used by both designers and manufacturers of combat rations. They represent the minimal levels of nutrients that should be in the ration. There are two types of NSORs. The first apply to standard operational rations which are intended to be nutritionally complete (if consumed as indi- cated) and can be used for long periods of time. The second apply to specialized rations in situations where mission requirements impose size, weight and/or wa- ter content limitations to the ration composition that significantly restrict energy and nutrient density. These restricted energy rations are inappropriate as a sole, continuous, long-term source of subsistence. To provide some flexibility to ration designers but to avoid potential ad- verse effects of inadequate intakes, the average meal menu should meet one- third of the NSOR level but no single meal menu should be 20 percent above (if standard is a maximum, such as for sodium) or below (if standard is a minimum, such as for vitamin C) one-third of the NSOR limits (Baker-Fulco et al., 2001). For essential minerals, which are the nutrients of interest for the current task, the standards have been set at the highest gender-specific RDA or AI for adults. The NSORs for restricted rations are set arbitrarily by the military at 50 percent of the corresponding operational ration standard for each nutrient. Rations developers who use these standards also consider other food-related factors--such as bioavailability and storage losses of nutrients--that may influ- ence the actual nutrient level needed in the food items.
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Representative terms from entire chapter: