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5 Answers to the Military's Questions This chapter summarizes answers to the specific questions that were posed to the committee. In an attempt to summarize the answers, descriptions of criti- cal issues are merely reviewed. For more details and in-depth discussions of the critical issues the reader is referred to Chapters 2, 3, and 4 where full discus- sions, including explanations of inconsistent results or needs for further research for promising areas are included. Therefore, for each question and to avoid re- dundancy, only a summary of the issues already addressed in other chapters are presented here; the specific recommendations for each question are also included. QUESTIONS 1 AND 2 1. Which dietary minerals are likely to have an impact on human per- formance? 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 miner- als 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 two- to three- day recovery periods that include garrison dining)? Questions 1 and 2 are closely related and will be addressed together. Based on the military's information on mineral status and performance levels (Friedl, 2005; see Friedl in Appendix B) and the commmittee's experience with the functions, metabolism, and nutrient intake requirements, six minerals--calcium, copper, iron, magnesium, selenium, and zinc--were deemed important for mili- tary performance. 219
220 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL The committee used information (the mineral composition for 3 different MREs containing 24 menus each and 3 different FSRs menus) provided by the U.S. Army Research Institute of Environmental Medicine to evaluate the se- lected minerals' content adequacy in the operational rations (see Appendix C). Content adequacy can be evaluated considering groups (i.e., is the mineral con- tent adequate for the population?) or individuals (i.e., is the mineral content adequate for each individual?). Because the committee had no data on the distri- bution of mineral intakes for military garrison training, the mineral content of menus for the population could not be evaluated. Instead, the recommended RDAMGT and AIMGT (Recommended Dietary Allowance and Adequate Intake for military garrison training, respectively) were used as benchmarks to evaluate mineral content adequacy of the various rations for individuals. (see Question 4 for the process on arriving at the new RDAMGT and AIMGT). For this exercise, the committee assumed that women will consume two MREs and men will consume three MREs. The average mineral content levels for each MRE or FSR were used to assess adequacy; in other words, three MREs or two MREs need to meet (without exceeding the Tolerable Upper Intake Lev- els [ULs]), at the minimum, the specific RDAMGT and AIMGT recommended by this committee for men and women, respectively. The content of one FSR needs to be within the recommended range for assault rations (IOM, 2006). However, consideration should be given to the fact that, although the average content might be adequate, some menus within each ration seem to be low in specific minerals (e.g., calcium). It was assumed for this study that the mix of menu choices eaten daily are sufficient to meet the average level of the minerals of interest. How- ever, individuals' repeated selection of MREs that have low levels of particular minerals presents a risk of developing mineral deficiencies. The committee rec- ommends, therefore, that menus on the low end of the mineral content range be revised to meet the recommended intake levels for both men and women. On average most mineral content in rations will meet the committee's rec- ommendations (see Table 5-1, Chapter 3 for details). The exceptions are the iron content for women (RDAMGT = 24 mg/day versus an average of 18 mg in two MREs) and the zinc content for men (RDAMGT = 15 mg/day versus an average of about 14 mg in three MREs) and women (RDAMGT = 11 mg/day versus an average of about 9 mg in two MREs). The mineral content of the FSRs appears to meet the recommendations of the current committee, except for calcium, whose average content in the FSRs (673 mg) is slightly lower than recommended in the Institute of Medicine (IOM) report, Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations (750 mg, see Table 5-1) (2006). The committee concluded that more research is needed on calcium intake and any associated risk of kidney-stone formation before lowering the range of calcium in assault rations below the AI of 1,000 mg/day. The level of specific mineral intakes depends not only on the mineral con- tent of the rations but also on the rations' composition (i.e., interaction with
ANSWERS TO THE MILITARY'S QUESTIONS 221 TABLE 5-1 Mineral Intakes: Institute of Medicine Dietary Reference Intakes, Current Military Dietary Reference Intakes, Recommended Intakes for Garrison Training (EARMGT, RDAMGT, or AIMGT), and Recommended Levels for Assault Rations IOM RDA Levels For Nutrient or AI MDRI RDAMGT or AIMGT Assault Rations* Calcium (mg) Male 1,000 1,000 1,000 750850 Female 1,000 1,000 1,000 Copper (µg) Male 900 ND 1,800 9001,600 Female 900 ND 1,500 Iron (mg) Male 8 10 14 818 Female 18 15 24 Magnesium (mg) Male 420 420 420 400550 Female 320 320 320 Selenium (µg) Male 55 55 55 55230 Female 55 55 55 Zinc (mg) Male 11 15 15 1125 Female 8 12 11 NOTE: AI = Adequate Intake; EAR = Estimated Average Requirement; MDRI = Military Dietary Reference Intake; MGT = military garrison training; ND = not determined; RDA = Recommended Dietary Allowance. *IOM (2006). other components), food consumption behavior (e.g., do soldiers eat 100 percent of the rations?), and ration selection. Therefore, the committee concluded that surveys on actual mineral intake or status--especially for calcium and iron-- need to be conducted for the adequacy of the rations' mineral content to be evaluated and that for food composition analysis should continue to be performed. QUESTION 3 3. During garrison training, do weight loss diets (energy or macronutri- ent restricted) have the potential to lead to deficiencies of specific essential minerals? The principal determinant of mineral balance in healthy individuals who are physically active is that there be an adequate intake of all essential nutrients.
222 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL This situation would be the usual condition for soldiers in garrison training who eat prepared foods or rations that have intakes meeting the military's dietary reference intake (MDRI) requirements (U.S. Departments of the Army, Navy, and Air Force, 2001). Under some field conditions, particularly during opera- tions in training or active combat, weight loss primarily caused by inadequate intakes in relation to increases in energy expenditure is common. However, un- der other conditions weight constancy or even weight gain is common (as is reported to be characteristic of the current operations in Iraq). Mineral status during weight loss depends significantly on the severity of caloric deprivation, macronutrient composition of the diet, and mineral intake. The most severe caloric deficiency is due to total fasting, which would never be intended during military operations. Without energy or mineral intake but with adequate fluid intake, mineral balances would be negative for all of the minerals under consideration, including calcium, magnesium, phosphorus, sodium, potas- sium, zinc, selenium, copper, and iron. Such a regimen can be tolerated in obese individuals for many months so long as there is sufficient fat and water, and very obese individuals have tolerated fasting (receiving only noncaloric liquids) for up to 249 days (Bloom, 1959; Runcie and Thomson, 1970; Thomson et al., 1966). Even though there would be substantial lean-tissue loss (approximately one-quarter to one-third of the weight loss) as well as bone loss and reduced exercise capacity, death from protein-calorie malnutrition likely would occur only when there was lean-tissue loss representing about one-half of the lean tissue or about 40 percent of the initial body weight (Henry, 1990). Dysphoria, postural hypotension, and changes in mood are frequent in the early stages of starvation, but after initial adaptation to a fasting state (which occurs over the first week or so), substantial deficits in physical performance are not found until approximately a 10-percent weight loss is reached. For normal-weight individu- als (the expectation is that most individuals found in military settings would be of normal weight), total fasting is much less well tolerated, even initially. Mor- tality would happen probably within 611 weeks, and physical performance would be very poor in the later weeks. Death would take place due to an absence of stored fat sufficient to meet the energy deficit; this claim is based on the experience of the Irish Republican Army hunger strikers in Northern Ireland (Leiter and Marliss, 1982). Thus, death usually would occur because of an acute lack of energy caused by depleted body energy stores. A less severe, but still hypocaloric, diet would be described as one that provides some intake but less, often far less, than about 50 percent of caloric needs. A substantial experience with such diets occurred in the 1970s when liquid protein diets based on collagen were used as the principal source of pro- tein and calories, leading to multiple mineral deficiencies. A number of deaths occurred in obese individuals consuming such regimens for periods of at least several months; the deaths were thought to be due to a combination of lean tissue loss and mineral deficiencies, particularly of potassium, copper, and phosphorus
ANSWERS TO THE MILITARY'S QUESTIONS 223 (Amatruda et al., 1983; Isner et al., 1979; Klevay, 1979). Subsequently, similar degrees of caloric deprivation--but with adequate mineral and high biologic value protein intake, as found in semistarvation ketogenic diets--were effective for short-term weight loss of considerable degree without causing undue safety concerns in obese individuals (Palgi et al., 1985). These cases of caloric depriva- tion emphasize the importance of protein composition and mineral intake under the related conditions. However, the use of this type of regimen for military purposes was discontinued--except for unanticipated combat situations--after experience with a severely hypocaloric diet, which met less than 50 percent of the energy needs during Ranger training, led to substantial and unacceptable clinical deficits associated with greater than 10-percent weight loss (Moore et al., 1992). Caloric deficits of about 1,0001,500 kilocalories that still provide greater than 50 percent of caloric needs are well tolerated clinically for weight loss in the overweight and obese as well as during short-term military operations (IOM, 2006). Similar diets used for intentional weight loss on an outpatient basis rarely lead to a 10-percent weight loss, frequently because of a lack of compliance, and thus, lead to unchanged or even improved physical performance. In military combat settings, where other food sources are unavailable, it would be good clinical policy to avoid prolonged periods of hypocaloric feeding, which could lead to weight losses greater than 10 percent. The principal variables, in terms of mineral balance, of these mildly hypo- caloric diets are the macronutrient content (particularly if high or low in protein) and the mineral content. The minerals of greatest interest are calcium, magne- sium, and zinc, since the likely duration of use intended in a military context makes substantial imbalances for iron, copper, and selenium of little clinical relevance, particularly when these minerals are provided daily in MDRI quanti- ties. Of the three minerals of greatest interest, magnesium is the least likely to present a clinical problem, because the body can reduce urinary magnesium losses to minute levels, even without limiting magnesium intake. Zinc is of greater concern because of its importance in immune function and the potential for occurrence of diarrheal illness in military operations [as mentioned in Hamer (2005) and in Hamer in Appendix B, diarrhea is a risk factor for zinc losses]. If however there is an absence of diarrhea and if zinc is consumed at MDRI quan- tities, then the net zinc lost due to weight loss on a hypocaloric diet reflects net nitrogen loss. Thus, minimization of net nitrogen loss would be the greater con- cern when compared with zinc loss. Studies of elemental balance in underweight subjects have demonstrated that lean tissue has a fixed ratio of nitrogen to potassium, phosphorus, and so- dium, and the three latter must all be provided in minimal amounts for lean tissue to be maintained (Rudman et al., 1975). However, these amounts are met easily by each of the minerals' RDA. Calcium balance under these conditions is dependent on phosphorus and sodium, since bone-mineral repletion can not oc-
224 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL cur in the absence of these elements (Rudman et al., 1975). Thus, the most important variable is a relatively high protein intake of 1.21.5 g/kg (IOM, 2006); benefits of a high-protein diet include a reduction in hunger (when compared with an isocaloric diet high in carbohydrates) as well as a number of metabolic benefits related to insulin action (Noakes et al., 2005). Bone turnover was in- creased with both the high-protein and high-carbohydrate diets and included an increase in both serum osteocalcin and urinary collagen cross-link excretion, markers of bone resorption (Noakes et al., 2005). The iron status (also of both diets) was well maintained and indicated no changes in hemoglobin, even though dietary iron reached RDA levels only in the high-protein diet (Noakes et al., 2005). This finding is in contrast to that of Kretsch et al. (1998) where research indicated that obese women consuming a diet providing approximately 50 percent of estimated calories led to a significant reduction in hemoglobin and hematocrit and a reduction in cognitive ability related to sustained attention. The difference in findings may be linked to the iron status at the beginning of the diet period, which appeared to be better in the former study, and perhaps as well to the higher protein intake particularly in the high-protein group (Kretsch et al., 1998; Noakes et al., 2005). The protein intake in the Kretsch et al. (1998) study was not regulated and, thus, was likely to be less than 1 g/kg. A number of studies have demonstrated the importance of higher protein in- takes to improve preservation of lean tissue during weight loss when the protein is substituted with isocaloric amounts of carbohydrate (Baba et al., 1999; Farnsworth et al., 2003; Piatti et al., 1994). However, similar benefits in terms of hunger reduction and improvement in lipid metabolism can be achieved if the carbohy- drates are provided in larger quantities as long as those used have a low glycemic index (Pereira et al., 2004). Nonetheless, for the maximal preservation of body protein with weight loss, protein intakes of 1.21.5 g/kg would need to be present. When the dietary protein is in this range, whether the protein is mostly from high- calcium dairy products (2,400 mg/day) or from mixed-protein and moderate cal- cium products (500 mg/day of calcium), the effects on fasting insulin, lipids, blood pressure, and fibrinolysis and endothelial function (i.e., metabolic parameters) are independent of diet (Bowen et al., 2005). A study from the same group did show, however, that the lower calcium intake caused a larger increase in urinary deoxypyridinoline as a marker of bone breakdown and an increase in osteocalcin in the mixed-protein diet, only suggesting a benefit for the high-dairy protein with its higher calcium in reducing bone turnover (Bowen et al., 2004). Calcium is the principal mineral of concern regarding weight loss diets, because its metabolism may be altered by dietary composition. Evidence shows that weight loss--in overweight and obese subjects as well as in postmenopausal women consuming their usual calcium intake--is associated with a loss in bone mass (Hannan et al., 2000; Ricci et al., 2001) and an increase in fracture risk (Langlois et al., 1996). Although many minerals are essential for bone health and
ANSWERS TO THE MILITARY'S QUESTIONS 225 function, the risk of calcium inadequacy in the diet is higher than risks of other deficiencies. Because of its role in bone health and potential alterations in me- tabolism if intake is inadequate, calcium is the principal mineral of concern regarding weight loss diets. In overweight postmenopausal women, weight loss resulting from moderately hypocaloric intakes leads to reduced calcium absorp- tion, but net positive calcium balance can be achieved with 1.8 g/day of calcium as compared to 1.0 g/day (Cifuentes et al., 2004). A follow-up study demon- strated that calcium supplementation at 1.7 g/day minimizes bone loss during weight loss in overweight postmenopausal women (Riedt et al., 2005). An ear- lier study on obese postmenopausal women also showed that calcium supple- mentation of 1 g/day reduced urinary collagen pyridinium crosslinks, osteocalcin, and parathormone during weight loss (Ricci et al., 1998). The effect was not observed in obese premenopausal women (Shapses et al., 2001). The relationships between weight loss, level of protein intake, calcium in- take, and bone health have not been studied in physically active premenopausal women, a population that would be relevant to the military. However, to safe- guard against potential bone deficiency during weight loss higher protein intakes and calcium intakes of at least 1 g/day--with, perhaps, even greater benefit if intakes are in the 1,5001,700 mg/day range--are recommended. These recom- mended intake levels should be tested on young adults who are intentionally dieting for weight loss; if weight loss is a consequence of the training itself and the reduced energy intakes found in military scenarios, then, the high protein/ high calcium intake should be tested in not obese, or even overweight soldiers. With regard to weight loss and its impact on the other essential minerals-- including magnesium, zinc, selenium, copper, and iron--there is little evidence to show that there is either (1) a reduced efficiency of use, and thus a need for increased mineral intakes, or (2) a reduced need for mineral intakes during peri- ods of modest hypocaloric intakes (1,0001,500 kcal/day) that provide at least 50 percent of daily caloric needs. Hence, providing the essential minerals in the amounts proposed in this report should be sufficient to maintain optimal function during weight loss. QUESTION 4 4. Do the high-performance activities of soldiers cause excessive min- eral loss, thereby raising the mineral dietary requirements? There is evidence to believe that exercise-related mineral loss, occurring mainly through the sweat but also through feces and urine, might be significant. However, many of the studies addressing mineral secretion and exercise cannot be applied to the military environment, or have design flaws, or both. Nonethe- less, because of the number of studies suggesting that the losses are real, the committee has increased the requirements for iron, copper, and zinc, based on the best available data and on their expertise and reasonable judgements (see
226 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL Table 5-1). Chapter 3 details the recommendations. These values should be con- sidered provisional and should be reconsidered after new studies (following the design recommendations in Chapter 4) become available. The data for copper are variable partially due to differences in sweat collec- tion and copper quantification methods. Based on the best data available, the committee concluded that male soldiers in garrison training will lose at least 500 µg/day of copper (female soldiers will lose at least 350 µg/day) through sweat. The data on iron, with regard to sweat losses, come from civilian studies and vary considerably. However, the committee concluded that sweat losses might be significant during exercise and need to be considered when establishing iron requirements. The committee believes soldiers could lose as much as 1 mg/day of iron (0.6 mg/day for women) through sweat. Likewise, studies on zinc increases in the sweat generated by exercise reveal that as much as 2.0 mg/day and 1.3 mg/day, for men and women, respectively, could be lost because of garrison training conditions. Calcium requirements may also be higher under the stress of physical activity and environmental conditions normally experienced by military personnel in garri- son training. There is evidence indicating that factors like increased sweat losses, loss of bone mass with oral contraceptives, or increased losses with weight loss could raise the requirements. Other factors encountered during training, however, such as the beneficial effects of exercise on bone metabolism, may compensate for those losses. All these various factors that affect calcium and bone metabolism act concomitantly and the overall impact of garrison training on requirements is still uncertain. The committee concluded that there is not enough evidence to change the calcium dietary requirements for soldiers in garrison training but urged re- searchers to conduct appropriate studies that could address this issue. In all cases, acclimatization to heat and exercise is likely to occur, but ques- tions regarding the extent of acclimatization remain unanswered. In addition, new models (designed according to Chapter 4's recommendations) that better simulate military garrison training conditions need to be developed, and the resulting data on mineral losses must be collected. There was not enough data to assess whether or not physical activity would increase urinary or fecal mineral losses. However, there are suggestions to this effect (i.e., substantial fecal iron losses could occur with extreme exercise); research in this area also is warranted (see Chapter 4). Nutrient standards for military personnel in garrison training or in opera- tions should be derived as indicated in Box 5-1. Based on the sweat loss find- ings, the committee adjusted the IOM Estimated Average Requirements (EARs) and calculated new EARs and RDAs (EARsMGT and RDAsMGT) for copper, iron, and zinc (see Table 5-1). The committee recommends using the current IOM AI level of calcium for the general population as the AIMGT until more research becomes available (see Table 5-1).
ANSWERS TO THE MILITARY'S QUESTIONS 227 BOX 5-1 Establishing Nutrient Standards for Military Personnel Recommendation: Nutrient standards for military personnel in garrison training should be derived as follows: 1. EARMGT : Modify the current IOM EAR by adjusting for the variable of interest (e.g., level of sweat losses). 2. RDAMGT : Add 2 × SD (standard deviation) of the EARMGT, to ensure that 97 98 percent of soldiers will have adequate intake. There were not enough data addressing the impact of sweat losses on mag- nesium and selenium levels to recommend an increase in dietary intake (see Chapter 3 for details). Research on sweat, urinary, and fecal losses under mili- tary garrison training conditions also is warranted (see Chapter 4). The commit- tee recommends using the current IOM RDAs for magnesium and selenium for the general population as the RDAMGT until more research becomes available (see Table 5-1). QUESTION 5 5. Is there any scientific evidence that mineral supplements (individu- ally or in combination) improve soldiers' performance? There is no definitive evidence that specific mineral supplementation in amounts greater than those recommended as dietary requirements will improve soldiers' physical or cognitive performance. Therefore, the committee has not recommended the intake of supplements to this effect. There are, however, sci- entific studies that strongly suggest the potential for improved performance and are summarized below (see Chapter 3 for details). A positive relationship between physical activity and calcium intake on bone density has been demonstrated in postmenopausal women and children, although not in age groups or lifestyles relevant to the military (Lau et al., 1992; Prince et al., 1991; Specker, 1996; Specker and Binkley, 2003). However, related research with premenopausal women has shown mixed results (Recker et al., 1992; Valimaki et al., 1994). The type of exercise may influence bone turnover as well as dietary intake. In research conducted on cadets, only males showed that milk consumption positively influences bone health; there was also a significant im- pact on cortical thickness related to milk consumption and exercise (Nieves, 2005; see Nieves in Appendix B). Calcium also appears to improve mood states, especially premenstrual distress syndrome (PMS) and depression (Penland and Johnson, 1993; Thys-Jacobs et al., 1989). Although results are encouraging for
228 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL calcium to relieve negative mood states, this has been done only with civilians and nonstressful situations; this suggestion needs to be demonstrated under the environmental and stressful conditions of garrison training. The reader is re- ferred to Chapter 3 for more details. Although the few studies performed in the military population do not sug- gest a relationship between iron status and cognition and mood states, there is sufficient evidence from studies in the civilian population that supports an asso- ciation between iron status and improved cognitive functions and behavior (e.g., Bruner et al., 1996; Groner et al., 1986, see Chapter 3). Some of these conclu- sions come from studies on iron deficiency. One of the pieces of evidence comes from a 16-week intervention study using women who, as part of the study, were provided with iron supplements (see Beard and Murray Kolb in Appendix B). After 16 weeks, some women had improved their iron status independently of the iron supplementation. There was a strong association between the women who reached the highest iron status (due to iron supplementation or other rea- sons) and improved measurements of attention, learning skills, and memory func- tions. Although one cannot ensure that iron supplementation will have a benefi- cial effect in all cases, it appears that improved iron status, possibly beyond the current recommended 15 µg/L of ferritin (level at which iron stores are present), may have beneficial effects in cognitive functions relevant for the military. Studies conducted to determine the effects of iron supplementation on mood states also indicate that depression can be alleviated by treating iron deficiency (Beard et al., 2005; Corwin et al., 2003). Although there is no doubt that the data are promising, all of the studies linking cognition and behavior with iron status have been done with civilians. Therefore, the committee concluded that before requirements for iron are increased with the objective of improving cognitive performance or mood states, more research is needed focusing on the subjects and environment of interest to the military. A few studies also have been performed on the potential relationship be- tween magnesium nutrition and improved effects of sleep deprivation that might affect future recommendations for military personnel. The association between selenium and zinc and mood states also has garnered interest. The data for these relationships, though, are still preliminary and, thus, merely suggestive. Taken all the research together, the committee concluded there is no scien- tific evidence to raise the recommendations for minerals with the objective of improving physical or cognitive performance or behavior. The committee also determined that it would be worthwhile to allocate enough resources for answer- ing questions on the potential effects of supplemental calcium on physical per- formance and mood states, supplemental iron on cognitive functions, and supple- mental magnesium on sleep deprivation effects and mood states. In addition, the relationship between supplemental zinc and cognition and mood states, as well as supplemental selenium and improvement of mood states, also could be con- sidered (see Chapter 4).
ANSWERS TO THE MILITARY'S QUESTIONS 229 QUESTION 6 6. Are the Military Dietary Reference Intakes (MDRIs) for dietary min- erals reflective of the Institute of Medicine (IOM) Dietary Reference In- takes (Recommended Dietary Allowances [RDAs] or Adequate Intakes [AIs])? Should the MDRIs follow the IOM RDA or AIs or should differ- ences persist because of the specific needs of soldiers? The MDRIs have been developed as a variant of the IOM Dietary Reference Intakes (DRIs) to account for the different environments and physical activity encountered by soldiers and to plan appropriate nutrient intakes and rations for them. The MDRIs and the nutritional standards for operational rations (NSORs) were established most recently in 2001 and were based on the IOM DRIs that were current at that time (U.S. Departments of the Army, Navy, and Air Force, 2001). Many of the MDRI values are similar to the DRIs, with the notable exception of sodium. The current MDRIs for minerals are the same as the IOM RDAs or AIs. There are reasons, however, to establish reference nutrient intakes that would apply specifically to the military population and help them to maintain a nutrient balance. First, the military population is different from civilians in terms of anthropometric criteria--that is, military personnel are slightly different in height, weight, and body fat and are generally more physically fit--and perfor- mance activity levels (typically higher in soldiers). Mineral values in the MDRIs should reflect the differences in anthropometry and in the mineral losses caused by high-performance activity. Second, the military lifestyle includes unique circumstances that are rarely encountered by civilians. These circumstances include multiple physical and psychological stressors (e.g., intense and continuous exercise while carrying heavy weight, sleep deprivation, stressful combat situations, extreme weather conditions) that can alter a soldier's physiology. The third reason for establishing military-specific nutrient requirements is to optimize the health and performance of enlisted men and women. The criteria for establishing requirements for the general population by the IOM has been to maintain health, so most of the data would ideally come from balance studies. However, one of the military's main objectives is to suceed in operations that demand ultimate physical and cognitive performance--consequently, if perfor- mance benefits are demonstrated, then the military would recommend higher nutrient levels. As science emerges regarding the unique nutrient needs of mili- tary personnel, additional adjustments will be necessary to meet those needs. The MDRIs should continue to reflect the IOM DRIs, with modifications made to specific nutrient requirements if sufficient scientific evidence demon- strates related needs and benefits. Also, the MDRIs can be used as guidelines for rations development for the individual soldier. The IOM DRIs can be used for dietary assessment and planning to guaran- tee a low prevalence of inadequate nutrient intakes (IOM, 2000, 2003). To plan
230 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL menus or rations for a large group, planners should know the EAR (and its distribution) of the target population, not only the mean and standard deviation, but also the percentile intake levels. However, when planning diets for individu- als, using only the RDAs or AIs is appropriate and sufficient (IOM, 2003). The MDRIs could be used to plan and assess menus for military personnel in the same way that the IOM DRIs are used for civilians. The difficulty in assessing the nutritional adequacy of menus for soldiers in garrison training is, as mentioned previously, that determinations will depend not only on the mean or median intakes but also on the range of the intake distribution, which is unknown for the military population. Instead, MDRIs could be used by cafeteria menu planners as a useful benchmark for what levels of nutrients are needed in foods on the menus. The IOM report Applications in Dietary Planning (IOM, 2003) should serve as a guide for using the MDRIs to plan the diets of military personnel. For the present, food-service managers should guarantee that cafeteria food is nutritionally diverse (contains selections from all food groups) and adequate, so that the options offered are likely to meet an individual's MDRI. To assist in the design of cafeteria food choices, food- service managers should include dietitians and nutritionists who are capable of applying nutrition guides, such as the Dietary Guidelines for Americans (http://www.healthierus.gov/dietaryguidelines/) and MyPyramid (http://www.my pyramid.gov/), that will meet the military's needs. Although the nutrient intake levels for soldiers who eat rations are unknown, it can be assumed safely that they will not vary too much if all of the rations issued are consumed. When planning, rations should meet the new military MDRIs (RDAMGT or AIMGT) for minerals. In situations where gender differences exist, rations should contain the highest recommended amounts, but those amounts should remain lower than the UL for the age range. Hence, the current NSORs based on MDRIs are established to represent the minimal levels of nutri- ents in operational rations. When adjusted as described, RDAMGT (and AIMGT) would be the basis of NSORs and would provide adequate levels for military personnel in garrison training. The committee supports the use of NSORs--modified accordingly as new sci- entific data become available--as minimum levels of nutrients in operational rations. The NSORs might vary depending on specific military situations; for instance, NSORs for military garrison training and for sustained operations may differ. QUESTION 7 7. How do changes in drinking water sources during military deploy- ment affect the balance of essential dietary minerals (e.g., U.S. public water supply versus bottled water versus field purification water)? The military's great efforts to educate soldiers on the need for water con- sumption have resulted in an improved conciousness regarding water intake.
ANSWERS TO THE MILITARY'S QUESTIONS 231 Consequently, water could become a method to deliver minerals. By virtue of the diverse water sources processed for the military, water could be a source of mineral intake variation with potential consequences on military performance. However, due to purification processes, it appears that the mineral content of the water for consumption is fairly low and would not contribute significantly to dietary intakes of minerals. The military provides soldiers with water from sources that meet the stan- dards for chemical and microbiological levels. During foreign deployments, drinking water may come from local water supplies and undergo additional treat- ments such as filtration and chlorination for bacterial control and removal of dissolved solids. For example, currently deployed soldiers consume mineral wa- ter that is produced at eight different sites and inspected by the military for bacteria, contaminants, and mineral content. In order for the water to be shipped to the soldiers, the mineral content has to be as low as what is found in U.S. commercially available mineral water; minerals are added in some cases (e.g., calcium is added to improve the taste). Soldiers also have access to nonbottled water that is essentially mineral free because it has been filtered through reverse osmosis purification units. The bioavailability of each mineral from water would depend on the salt form in the water. However, scant research exists to suggest that water can be a source of essential minerals. Considering the typical water consumption volumes of approximately 3 L/ day, the committee concluded that due to processes applied to fresh water for human consumption, differences in mineral content of water are not such that will affect the total intake levels of minerals by military personnel and do not contribute to the balance of essential dietary minerals. The committee concluded that the addition of calcium and magnesium to water consumed by military per- sonnel is warranted only when improving the taste is the desirable outcome. There is no evidence to suggest that the addition of substantial levels of calcium and magnesium would be an efficient strategy to meet nutritional standards; in addition, there is little research on bioavailability of minerals from water. Addi- tional cost evaluation of using water as a vehicle for minerals should be con- ducted if it is to be considered for implementation. REFERENCES Amatruda JM, Biddle TL, Patton ML, Lockwood DH. 1983. Vigorous supplementation of a hypocaloric diet prevents cardiac arrhythmias and mineral depletion. Am J Med 74(6):1016 1022. Baba NH, Sawaya S, Torbay N, Habbal Z, Azar S, Hashim SA. 1999. High protein vs high carbohy- drate hypoenergetic diet for the treatment of obese hyperinsulinemic subjects. Int J Obes Relat Metab Disord 23(11):12021206. Beard JL, Hendricks MK, Perez EM, Murray-Kolb LE, Berg A, Vernon-Feagans L, Irlam J, Isaacs W, Sive A, Tomlinson M. 2005. Maternal iron deficiency anemia affects postpartum emotions and cognition. J Nutr 135(2):267272.
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