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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations 3 General Considerations and Summary of the Ration Design This chapter summarizes the general approach followed in designing the nutrient composition of a ration for short-term, high-stress combat missions. The chapter also describes the main health concerns that were taken into consideration when recommending the nutrient composition of the ration. Some of the factors related to the food choices and ration design that might affect the level of consumption and availability of the required nutrients are also discussed. Finally, high-priority areas of research that should provide a basis for the future development of rations are highlighted. COMMITTEE’S APPROACH TO RATION DESIGN The committee used the Dietary Reference Intakes (DRIs) established by the Institute of Medicine for active young men (IOM, 2004) as the starting point or benchmark for nutrient content in formulating the assault ration because these values are the most authoritative and up-to-date standards available. Further adjustments were then made to meet the unique needs of soldiers involved in assault conditions. The Military Dietary Reference Intakes (US Departments of Army, Navy, and Air Force, 2001) were not used as the standard values because they have not yet been revised to reflect all of the new DRIs. Although the focus of this report is soldiers during sustained operations, the recommendations (see Table 3-1) may be applicable to physically fit nonmilitary personnel (e.g., firefighters, peacekeepers, and other civilian emergency personnel) under similar conditions of high-stress, intense physical activity, and negative energy balance and for the short periods of time outlined here. The committee emphasizes that this ration is meant to be used for repetitive three- to seven-day missions
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations TABLE 3-1 Ration Nutrient Composition Recommended by the Committee Nutrient or Energy Intake Recommended Amount Comments Energy Intake 2,400 kcal in basic ration Additional 400 kcal should be supplemented as carbohydrate in form of candy, gels, or powder to add to fluids, or all three. Macronutrients Protein 100–120 g Protein should be of high biological value. Preferable to add sources of protein with low-sulfur amino acids and low oxalate levels to minimize risk of kidney stone formation. Carbohydrate 350 g 100 g as a supplement Additional 100 g should be supplemented as carbohydrate in form of candy, gels, or powder to add to fluids, or all three. Amount of fructose as a monosaccharide should be limited to < 25 g. Fiber 15–17 g Naturally occurring or added. A mix of viscous, nonfermentable and nonviscous, fermentable fiber should be in the ration for gastrointestinal tract function. Fat 22–25% kcal 58–67 g Fat added to the ration should have a balanced mix of saturated, polyunsaturated, and monounsaturated fatty acids with palatability and stability the prime determinants of the specific mixture. Fat should contain 5–10% linoleic acid and 0.6–1.2% α-linolenic acid. Vitamins Vitamin A 300–900 µg RAE1 Could be added as preformed vitamin A or provitamin A carotenoids. Vitamin C 180–400 mg Highly labile in processed food. If added to foods, encapsulation should be considered to prevent degradation through interaction with pro-oxidants. Vitamin D 12.5–15 µg Estimates of dietary intake are not available. Range based on ensuring serum levels of 25-hydroxy-vitamin D. Vitamin E (α-tocopherol) 15–20 mg Should be added to foods since natural foods are mainly sources of γ- rather than α-tocopherol. Vitamin K No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods.2
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations Nutrient or Energy Intake Recommended Amount Comments Thiamin 1.6–3.4 mg Dependent on energy use and intake. Amount in foods would be adequate provided ration is at least 50% whole foods. Riboflavin 2.8–6.5 mg Dependent on energy use. Niacin 28–35 mg Dependent on energy use. The amount added to the ration should not be over 35 mg. Vitamin B6 2.7–3.9 mg Dependent on negative energy balance and loss of lean tissue. If a higher protein level is provided, the amount of vitamin B6 should be increased proportionally. Folate 400–560 µg Fortification may be needed. Vitamin B12 No recommended level Amount in foods would be adequate provided ration is at least 50 % whole foods. Biotin No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Pantothenic Acid No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Choline No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Minerals Calcium 750–850 mg Major concern for higher levels is the potential formation of kidney stones. Chromium No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Copper 900–1,600 µg If added to foods, encapsulation should be considered due to its pro-oxidant activity. Iodine 150–770 µg Could be added as iodized salt. Iron 8–18 mg If added to foods, encapsulation should be considered due to its pro-oxidant activity. Palatability should determine the amount in ration foods.
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations Nutrient or Energy Intake Recommended Amount Comments Magnesium 400–550 mg No more than 350 mg of magnesium salts should be present to meet the minimum daily amount of magnesium recommended. The rest should come from food sources. Also, if salt needs to be added and taste becomes objectionable, encapsulation should be considered. Manganese No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Molybdenum No recommended level Amount in foods would be adequate provided ration is at least 50% whole foods. Phosphorus 700–2,500 mg Because inorganic phosphates may cause diarrhea, it is recommended that they are added only up to 700 mg. Intakes above this amount should come from food sources only. Potassium Aim to 3.3–4.7 g Foods naturally high in potassium should be included in ration; if added to foods to achieve recommended levels, taste problems might be encountered. Selenium 55–230 µg No clear evidence of effects as an enhancer of immune function or performance. Sodium ≥3 g up to 12 g as supplement For individuals who lose salt in excess or when in extremely hot or strenuous situations, sodium could be supplemented up to 12 g total. Part of this amount should be included in the form of candy, gels, or powder to add to fluids. Palatability will limit addition of sodium to these products; therefore, salt tablets should also be provided under medical guidance. Zinc 11–25 mg If it needs to be added and taste becomes objectionable, encapsulation should be considered. Ergogenics Caffeine 100–600 mg Not more than 600 mg in a single dose. There is no evidence of dehydration at this level. 1RAE = retinol activity equivalents. 2Whole foods = food items prepared to preserve natural nutritive value.
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations that last for a maximum total period of one month and that include recovery periods between missions of about 24–72 hours. Energy and Macronutrients To develop the recommendation on the total caloric intake of the ration, the committee integrated information from several sources. First, the committee considered health risks and benefits of a high, medium, and low energy intake diet. Second, information provided to the committee regarding the eating behavior in the field was reviewed. The data included food preferences, degree of satisfaction, and actual consumption of the current rations. Finally, past studies demonstrating that soldiers do not eat enough when exposed to the high-stress situations in the field (IOM, 1995) were considered. This undereating is attributed to an array of psychological factors that are difficult to control. In fact, data collected during training exercises of various military groups (e.g., special operation forces, marines) indicate that under stressful field conditions soldiers consume an average energy intake of 2,400 kcal (see Montain, 2004 in Appendix B). This level of intake is not enough to maintain body weight; however, the weight loss is moderate if the period of low energy intake is not sustained. Taking this information into account, the committee concluded that a ration with a caloric content of 2,400 kcal—if designed with adequate macronutrients and micronutrients, and eaten entirely and for short periods of time such as three to seven days up to a month—would not pose any health risks. With the expected energy expenditures of 4,500 kcal/day during the missions, it is possible that some soldiers might lose as much as 10 percent body weight before the end of the month, even with refeeding between missions; this degree of weight loss could result in adverse but mild performance defects. Therefore, it is recommended that weight loss be measured after one month of use; if weight loss is higher than 10 percent for a soldier, he should not be sent on assault missions until weight is regained to within 5 percent of initial weight. The committee emphasizes that the ration nutrient contents recommended here are meant to be consumed for the short-term missions assumed in this report (three- to seven-day missions that last for a maximum total period of one month), not to substitute for longer periods in which Meals, Ready-to-Eat (MREs) or menus from food services constitute a more appropriate diet. The distribution, level, and type of macronutrients for the ration (see Box 3-1) were established by considering the major health risks that might be posed by eating a hypocaloric diet in a combat situation. One major health risk that needs remediation is the excessive weight loss that occurs when the energy intake is below the energy output. The typical energy deficit of 50 percent seen in combat operations leads to a negative nitrogen balance that can result in muscle loss, fatigue, and loss of performance. To minimize these potential consequences, the committee recommends a protein level of 1.2–1.5 g/kg of body weight per day,
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations BOX 3-1 General Design of the Recommended Assault Ration Basic Ration: Protein 100–120 g (400–480 kcal; 17–20% kcal) Carbohydrate 350 g (1,400 kcal; 58 % kcal) Fat 58–67 g (520–600 kcal; 22–25% kcal) Water 105 g (assuming an average of 17% moisture) Total weight (kcal) 613–642 g (2,400 kcal) Carbohydrate (and Electrolyte) Supplement: Carbohydrate 100 g (400 kcal) Water 17 g (assuming an average of 17% moisture) Sodium up to 12 g (based on palatability) Potassium up to 3.3–4.7 g (based on palatability) Total Weight (kcal) 117 g (400 kcal) Salt Tablets (Available Through Medical Personnel): Sodium up to 12 g Potassium up to 4.7 g Total Weight 16.7 g Packaging: 181 g Total Weight 0.95 kg Total Energy Content 2,800 kcal NOTE: This ration is intended for use over three- to seven-day missions for up to a month. Prolonged and continuous use of these rations as a sole source of sustenance may lead to substantial weight loss. Constraints: weight of 3 lbs (1.36 kg) and volume of 0.12 cubic feet. or 100–120 g of total protein per day. This level of protein would spare muscle protein and decrease net nitrogen loss; in addition, it would maintain an adequate level of serum proteins needed as, for example, antioxidant enzymes as well as potentially maintain immune and cognitive functions. The carbohydrate content of the ration is an important energy source and also plays a role in maintaining gastrointestinal health. Strong evidence that carbohydrate enhances cognitive function is still lacking; therefore optimizing physical performance was the rationale for the 350 g of carbohydrate recommended for the basic ration. Numerous data, however, suggest that supplementing the diet with carbohydrate throughout periods of continuous physical exercise and stress not only increases energy intake but also helps maintain and optimize
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations physical performance. The supplementation of the basic ration with additional carbohydrate (up to 100 g or 400 kcal) is therefore deemed critical to optimizing performance; therefore, the committee recommends such carbohydrate supplementation in the form of gels, candy, or dry powder (to add to water) be available during combat missions. To maintain gastrointestinal health, a range of 15–17 g of a mix of both viscous, nonfermentable and nonviscous, fermentable fiber is recommended. The primary reason to add fat to the ration is to provide a readily digestible food source of high energy density. Fat is also critical for the palatability of the ration and to permit absorption of fat-soluble vitamins. Because this ration is meant to be completely consumed, it is important that the acceptability of the ration be optimized; therefore, a minimum amount of fat is required in the ration to provide palatability. In general, surveys show that high-fat foods are not preferred by soldiers in the field (personal communication, A. Young, USARIEM, August 9, 2004). The committee concluded that, among the macronutrients, adequate levels of protein and carbohydrate were a priority and that the remainder of the macronutrients (up to the energy level of 2,400 kcal) should be provided as fat. Considering published data on preferences of athletes and the energy constraints of the ration, the committee recommends providing between 58 and 67 g of fat and distributing it across a variety of foods. Micronutrients In making its recommendations for levels of micronutrients in the ration, the committee followed a general approach, which is described here. The levels recommended here are primarily based on Recommended Dietary Allowance (RDA) or Adequate Intake (AI) for 19- to 30-year-old males from DRI reports (IOM, 2004) and then modified by the committee after considering data in the literature about sweat losses and utilization under high energy expenditure and stress. Food developers designing these rations might encounter difficulties in adhering to a single level of a nutrient due to organoleptic issues, food technology issues, or the presence of certain micronutrients in foods in limited amounts. Therefore, to provide food developers flexibility, a range is recommended for most micronutrients. For most cases, the ranges are based on the RDA or AI and the 95th percentile of intake of the US population as reported in the National Health and Nutrition Examination Survey (NHANES) III, a recent population-based survey, or other surveys if NHANES III data were unavailable. To avoid adverse effects when the 95th percentile dietary intake is higher than the Tolerable Upper Intake Level (UL), then the UL is included as the upper limit of the recommended range. Unless deemed necessary to maintain health or improve performance and to avoid the addition of supplements to the extent possible, the committee recommends micronutrient levels that could be naturally occurring in foods feasible for
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations this ration; fortification of foods may result in adverse sensory effects, promote interactions with other nutrients, and, in addition, is costly. In cases such as potassium, however, it was recognized that food alone would not provide enough of a particular nutrient and that some form of supplementation might be needed. In other cases, such as for the trace elements molybdenum, manganese, and chromium, no recommendation is made because those minerals are widely distributed in foods and a deficiency is not anticipated during the short period of intake of these rations. Exceptions to this general approach are described for each particular micronutrient in Chapter 2 and include the following: (1) for the B vitamins, the committee considered the importance of energy expenditure when setting the recommendations, while for vitamin B6, negative energy balance and loss of protein were considered; (2) for vitamin C, the committee added 25 mg to account for the needs of smokers; and (3) for vitamin A, the committee recommends a minimum of 300 µg RAE (retinol activity equivalents) to minimize the risk of night blindness. In making recommendations for micronutrient requirements for soldiers during high-intensity physical activity, one factor that needs to be accounted for is micronutrient loss in the sweat or urine or both. Among factors causing increased sweat volume are exercise intensity and environmental temperature, both of which are relevant for this report. As noted in Chapter 2, data on micronutrient losses are lacking in most cases and research is needed. Although data are limited, these factors cannot be ignored when making recommendations. When specific data for additional micronutrient losses in sweat or urine during intense exercise in the heat (e.g., zinc and copper) was available, then the amount was added to the upper end level of the range recommended. In other cases, such as for sodium, an estimation of the maximum losses for intense exercise under hot climates and for salt losers was calculated from the data available on sweat sodium concentrations for different ambient conditions and activities and estimated total sweat volume. Where necessary, the committee cautions about the potential for nutrient oxidation, or interactions with other nutrients in the ration. Therefore, it advises that chemical analysis be performed on the final ration following appropriate shelf-life studies. The importance of nutrient stability and interactions is further discussed later in this chapter under the section entitled Food Matrix Considerations. In summary, in recommending levels of micronutrients, the committee considered DRIs, dietary intakes for the US population, health concerns specific to the circumstances (see below), cognitive and physical performance, heat stress, and sweat and other losses. For a summary of the recommendations for micronutrients, see Table 3-1.
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations Other Bioactives The committee reviewed (see Chapter 2) the effects of several bioactive substances due to their potential benefits in physical or cognitive performance. The reader is also referred to Costello (Costello and Chrousos, 2004 in Appendix B). Other bioactives is a broad category of components that are not considered essential nutrients but that have been suggested to function in particular cells or as performance enhancers. Caffeine is the only component for which there is compelling data showing effectiveness for combat soldiers and therefore only caffeine received the endorsement of the committee. Caffeine is often consumed in the field and its use for physical and cognitive performance was recommended in a recent Committee on Military Nutrition Research report (IOM, 2001). Some other bioactives are already consumed at liberty in either the sports community (e.g., L-carnitine, creatine, neurotransmitter precursors) or the general population (e.g., Ginkgo biloba and Ginseng extracts). Soldiers also consume these types of bioactives with the goal of increasing physical endurance. For the most part, neither the evidence for improving physical performance nor the potential adverse effects of their use or interactions with other nutrients is clear. One reason for these inconclusive results might be that the studies have not been conducted in a randomized and blinded manner. For example, it is uncertain whether creatine actually builds muscle tissue or simply increases muscle bulk due to water accumulation (Tarnopolsky et al., 2004). However, the literature is fairly compelling regarding the benefit of creatine supplementation in the enhancement of muscle strength during resistance training as well as improvement of repetitive bouts of high-intensity activity (Terjung et al., 2000). Due to its usage, the committee suggests pursuing randomized, blinded trials to elucidate the risks, including withdrawal effects, and potential benefits of taking creatine; ideally, these trials should be conducted under conditions that mimic combat situations. Flavonoids are a subclass of polyphenols that might provide some benefit as antioxidants against the oxidative stress occurring during intense exercise and mental activities. It is believed that the antioxidant properties of these compounds might act in a synergistic manner with other dietary antioxidants (e.g., vitamin C, vitamin E) or antioxidant enzyme system (Liu, 2004) but most of the research has been done in vitro. More in vivo studies are needed to explore this possibility. In the meantime, and consistent with previous statements in this report, the committee recommends including foods such as fruits, vegetables, tea, and chocolate that contain significant amounts of flavonoids. Supplementary Carbohydrate and Electrolytes As mentioned above, the supplementation of the basic ration with additional carbohydrate is critical to optimizing performance. Therefore, the committee
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations recommends that such supplementation in the form of gels, dry powder to add to water, or candy be available during combat missions. In this way, small amounts of carbohydrate will be supplied as an extra source of energy. Similarly, small amounts of extra sodium can be added in the form of powders to add to fluids or in candy or gels. Additional sodium can be made available in salt tablets under medical guidance. The extra sodium will ensure that, in cases of excessive salt loss such as under conditions of hot climate or for excessive salt losers, sodium balance is not compromised. HEALTH CONCERNS General Gastrointestinal Tract Considerations Among the possible effects on gut function by specific ration nutrients, the following were considered: Potential Effects on Diarrhea Literature reports indicate that diets very high in fructose may cause gastrointestinal distress and osmotic diarrhea. It is important to limit the use of fructose as a monosaccharide to less than 25 g (see Chapter 2) and measure its level in the final product, since there is some indication of high levels of fructose in the ration beverages. Potential Effects on Nausea There have been some reports on nausea caused by high amounts of dietary zinc; however, the levels recommended in the assault ration are unlikely to be high enough to cause nausea. Also, high amounts of potassium, particularly in the form of potassium chloride, are linked to unpleasant taste, nausea, gastrointestinal inflammation, and gut distress. Potassium is less likely to cause such effects in a food matrix. Although further research needs to be done on these points, the committee concludes that the levels of these nutrients in the assault ration are not excessive. Addition of Prebiotics or Probiotics Various probiotics were also considered for possible inclusion in the ration. The extremely long shelf-life required by the ration specifications precludes the use of any probiotic, since their stability to fulfill elements of long shelf-life is insufficient at this time.
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations General Immune Considerations Certain essential nutrients (vitamins A, C, B6, B12, E, pantothenic acid, folate, and minerals such as selenium, zinc, copper, iron, and phosphorus) are known to cause immunodeficiency when provided for prolonged periods (e.g., weeks or months) in less than required amounts. The proposed assault ration is designed to contain adequate amounts of each of these nutrients. Other nutrients (e.g., arginine, glutamine, vitamin C and E in large amounts, ω-3 fatty acids and β-glucan) and other bioactives (e.g., Echinacea extracts) have been proposed to enhance immune function. As described in this report, the current evidence does not support a recommendation to include them in the assault ration. General Dehydration Considerations Although the committee was not asked to consider water requirements in its recommendations for the proposed assault ration, certain hydration issues were considered important to the optimal composition of the ration. For example, since the sodium content would be closely linked to water needs, the committee recommends a dietary sodium content that would accommodate moderate sweat losses of 6.5–10.5 L/day. For those that lose salt in excess, supplemental salt would be required. Furthermore, the committee supports continued use of the camel-back to provide water and also recommends that a mechanism be developed to provide the option of flavoring the water so as to encourage fluid intake. Another important facet of diet design related to hydration is the potential for renal stone formation. Although the most important variable to reduce the risk of renal stone formation is water intake sufficient to meet sweat losses, sodium, calcium, and oxalate content of the proposed assault ration were also considered to minimize this complication. The effect of specific macronutrient levels, namely carbohydrate and protein, on water needs was also discussed. The importance of providing enough water during these missions so that water needs due to sweat losses and the nature of the ration are met, cannot be overemphasized. Finally, gastrointestinal fluid and electrolyte losses due to diarrhea illness can also severely stress water balance. Providing a palatable assault ration that will likely meet anticipated levels of energy intake under these short-term combat conditions should limit the use of local foods which might increase the risk of diarrheal disease. In addition, the recommendation of using fiber, both viscous and nonviscous, should support better gastrointestinal function. FOOD MATRIX CONSIDERATIONS Food rations meant for short-term, high-intensity operations use present a unique challenge to the product developer and nutritionist. With careful planning, it should be possible to provide complete nutritional needs in a restricted
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations potential decreased bioavailability due to interactions, the use of encapsulated forms for some nutrients may be necessary. Electrolytes (sodium and potassium) and other minerals (zinc and magnesium) are known to have objectionable tastes to some, possibly at the levels recommended. Palatability of the ration components is a primary concern. The ration is intended for short-term consumption, that is, during repetitive missions that last for three to seven days, possibly over a relatively short period of time, such as a month. Safe use of the ration is an important consideration. Although the rations could provide sufficient nutritional value for longer term if more than one ration is eaten, the committee does not recommend consuming two or more rations per day. Because the foods that will be included are highly processed, they may not provide as complete an array of food components as a regular diet. Also, the distribution of the energy-providing nutrients is atypical for US diets. Therefore, the committee’s recommendations assume a short-term consumption regimen. Monotony, induced by limited food choice, is known to reduce the amount of food consumed, as well as lower acceptability of the items (Kramer et al., 2001). Thus, providing a variety of acceptable products for the short term is necessary. Taste An important consideration under the high-intensity physical activity of combat situations is that rehydration must occur with replenishment of electrolytes. The high levels of electrolytes sodium and potassium recommended by the committee will affect the taste and flavor of the ration components. Most of the published work on taste quality and preference of electrolytes has been done on sodium. Very high or very low levels of salt in foods are generally liked less, but there is a strong dependence on the food matrix (Beauchamp et al., 1983; Drewnowski et al., 1996). The preferred level of salt in soups is about 200 mmol/L (approximately 500 mg sodium/100 mL). Processed foods, such as canned soups, can contain as much as 1,000 mg sodium per serving (240 mL). Addition of sodium and potassium salts via sports drinks or gels provides less than 50–100 mg per serving. The recommended level of sodium in a rehydration beverage is at least 50 mmol/L (Maughan and Shirreffs, 1997; Maughan et al., 1997). Palatability does not appear to be a problem with concentrations from 40–60 mmol/L (Passe, 2001; Shirreffs et al., 1996). Little research has been done on the taste sensations elicited by potassium, magnesium, or zinc in foods. Potassium chloride (KCl) is the most common form of potassium used in foods, primarily as a salt substitute. This compound has a bitter, soapy taste at high concentrations. Bertino et al. (1986) reported that palatability decreased for KCl in soup and crackers at 0.13 mol/L and 1.8 percent, respectively. Fortification with potassium salts is possible in baked products and liquid solutions, if the concentration is kept under 400 mg potassium/100 g and salts other than KCl (e.g., potassium bicarbonate and various potassium
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations phosphates) are used (Mentavlos, 2002). Magnesium also has a bitter taste that seems to be detectable at similar concentrations (0.3 mol/L; Delwiche et al., 2001). Zinc salts that are often included in nutritional supplements and mouth care products are known to produce astringent sensations, but not strong sour, bitter, sweet, or salty tastes (Keast, 2003). Calcium salts generally do not have objectionable tastes and may minimize other mineral taste sensations (Lawless et al., 2003). Nutrient Density and Satiety Much of the research on the impact of nutrient density on food intake is related to its potential link to obesity. The consumption of high-energy-density, high-fat foods is associated with increased total intake of calories (de Castro, 2004). How nutrient density affects the satiety value of various foods or food components is an important concept in formulating military rations. Factors affecting eating behaviors that lead to food underconsumption, an ongoing problem for troops in combat situations, were described in Not Eating Enough (IOM, 1995). The effects of food composition and nutrient density and their impact on satiety are recognized and detailed in that publication. From a biological standpoint, food consumption is driven by a feeling of hunger, which stimulates eating. Satiation occurs when the feeling of hunger dissipates, usually due to a feeling of fullness (Blundell et al., 1996). Satiety occurs after food is eaten, and this tends to delay the next eating bout. Merrill et al. (2004) considered satiety to be the result of both biological and psychological effects resulting from food consumption. Gerstein et al. (2004) point out that studies of macronutrient effects on satiety suggest that, when in isolation, protein is the most satiating macronutrient, followed by carbohydrates and fat. A number of recent studies, however, indicated that greater satiety results from consumption of foods higher in protein and carbohydrate than fat (see, for example, Blundell and MacDiarmid, 1997; Holt et al., 1999; Marmonier et al., 2000). Anderson and Moore (2004) reviewed studies of protein effects on food intake regulation in humans, and although they came to the same conclusion, these authors pointed out that further research is needed. Many of the observations of macronutrient impact on satiety were made with pure sources of the energy-providing nutrients, and not foods, which are mixtures of several of these and other nutrients (Bell et al., 1998; Rolls, 1995; Rolls and Shide, 1992). Some research shows that energy-dense foods that are rich in fat tend to have lower ability to lead to satiety (Holt et al., 1995). On the other hand, high-fat foods tend to be well liked, and because they are less likely to contribute to a feeling of fullness or satiation, they will be overconsumed (Blundell et al., 1996; Nasser et al., 2001). Foods high in sucrose have high satiety value (Holt et al., 1995), which suggests that a mix of carbohydrate-rich and fat-rich foods is needed to provide a balance in the assault ration. The satiety value of a variety of
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations Army rations was assessed by Merrill and coworkers (2002, 2004). Their research focus has been on “the perceptual consequences of eating” in an attempt to measure and predict the perceived satiety of meal ration components, including some from the FSR and MREs. These provide a preliminary database that could assist in further development of foods that will stimulate consumption of more calories and counter the underconsumption and weight loss observed under combat operations. Nutrient Stability and Possible Nutrient Interactions Vitamin stability and degradation in processed food and has been reviewed extensively (Gregory and Kirk, 1981; Karmas and Harris, 1988; Labuza and Riboh, 1982; Villota and Hawkes, 1992). Heat, light, ultraviolet and gamma radiation, oxidation, water content, and activity all influence the rate of loss (Gregory, 1996; Labuza, 1980; Nelson and Labuza, 1994). In addition, specific vitamins exhibit different rates of destruction. Water-soluble vitamins, such as ascorbic acid and folate, are subject to degradation in higher water content and water activity foods (Gregory, 1996; IOM, 2002). Fat-soluble vitamins, such as vitamins A, D, E, and K, are subject to oxidation, which is often accelerated by light and heat (Ottaway, 1993). When vitamins are added as fortificants, they are often encapsulated or coated. This technology provides a physical barrier, primarily to prevent nutrients from oxidation, catalytic reactions, and degradation and to prevent changes in flavor, color, or texture that might be affected by oxidation products. Numerous patented processes for doing this have been developed in recent years (Brazel, 1999; Risch and Reineccius, 1995). The actual procedure used for vitamin coating or encapsulation will depend on the vitamin’s properties, as well as the presence of pro-oxidants. Fat-soluble vitamins may be stabilized by antioxidants, including dl-α-tocopherol or butylated hydroxyanisole or butylated hydroxytoluene. Vitamin C can be coated with various substances, such as ethyl cellulose, cyclodextrins, or lipids, to prevent contact with iron, copper, or nickel. Encapsulation of vitamin C slows its degradation under high heat and moisture conditions (Uddin et al., 2001). It should also protect it from oxidation by metals, such as iron. Because vitamin C can enhance nonheme iron absorption from foods and improve absorption of nonchelated iron used for fortification, the interactions between these two nutrients has been considered in fortification programs (Hurrell, 2002b; IOM, 2000). The questions of iron absorption and iron bioavailability from iron fortificants has been addressed extensively in the context of alleviating global iron deficiency anemia (Foege, 2002; Hurrell, 2002a). Embedded in these discussions are references to the undesirable changes in color, flavor, and texture, as well as shelf-life stability due to lipid oxidation, caused by various iron fortificants. Sensory changes due to the various classes of iron compounds, however, are not well
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations documented, as reviewed by Bovell-Benjamin and Guinard (2003). Hurrell (2002b) pointed out that “the most soluble and absorbable iron compounds often cause unacceptable color and flavor changes when added to foods.” In a review of iron fortification, Hurrell et al. (2002) noted that iron is the most difficult mineral to add to food. Ferrous sulfate is the most common water-soluble form of iron used in infant formulas, bread, and pasta; however, fat oxidation catalyzed by this compound can cause loss of shelf-life due to flavor and color changes. Other less soluble forms such as ferrous fumarate and ferric saccharate can be used and they cause slightly less change in flavor, but have lower bioavailability. Elemental iron powder, specifically electrolytic iron powder, is often used for infant cereal fortification, but it, too, can cause color changes visible to the mother, but accepted by infants (Bovell-Benjamin and Guinard, 2003; Hurrell et al., 2002). Sodium iron ethylenediaminetetraacetic acid (Hurrell, 1997) and ferrous bisglycinate (Bovell-Benjamin et al., 2000) are among newer, more expensive forms of iron fortification that are being studied, and even they cause color changes. Encapsulated ferrous salts are available (Zlotkin et al., 2001) but not widely used due to the heat instability of some coatings and lack of information about bioavailability. In formulating the FSRs, encapsulation of vitamin C and use of various soluble forms of iron should be considered. Compared with vitamins, minerals are much more stable, even under extreme conditions of heat and humidity. Although some minerals are water-soluble, the likely food products will be relatively low in water content and water activity. When iron is added for fortification, care must be taken to protect vitamins A and C and thiamin, due to the possibility of accelerated degradation. Iron also catalyzes oxidative rancidity of polyunsaturated oils and fats, which can produce undesirable changes in color and flavor. Fortification of food with copper could accelerate vitamin C degradation and interfere with bioavailability of other minerals, such as zinc; however, copper is naturally present in food and would probably not be added. Zinc-copper interactions are not envisioned to present a concern at the levels recommended here. Iodine is stable in foods, and can be added to the ration in the form of iodized salt. Although some food manufacturers have had concerns about the use of iodized salt in processing due to possible effects on flavor and color, there is little evidence to support this concern (West et al., 1995). Shelf-Life Stability Standard procedures for shelf-life testing should be employed during the development and testing of the ration components. As noted in an earlier IOM report on an emergency relief food product (IOM, 2002), shelf-life testing is an integral part of the development process. Most commercial products do not have the extended storage life expected of either military or emergency foods. Accelerated shelf-life testing is often used to predict stability over long time periods
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations under extreme conditions (Labuza and Schmidl, 1985, 1988). Other prediction models have also been proposed (Cardelli and Labuza, 2001; Gacula and Singh, 1984; Nelson and Labuza, 1994). Decisions about shelf-life and length of storage are made based on changes in at least one characteristic of the food, such as sensory quality, vitamin content, or lipid oxidation. Changes due to aging include texture deterioration, browning due to Maillard Browning or oxidation, staling, and off-flavor development (Lawless and Heymann, 1999). Carefully planned shelf-life studies can lead to prediction models for storage stability (Labuza and Schmidl, 1988). Acceptable analytical techniques are critical to the success of conducting shelf-life studies and to guaranteeing specific levels of nutrients in the ration at the end of the projected storage period. The analysis of each ration component for vitamin and mineral content should be part of the routine quality control program. Sensory testing should also be integral to quality assurance. General Concerns and Recommendations An assault ration must provide a concentrated source of designated nutrients in foods that are highly acceptable to trained soldiers in physically and psychologically stressful situations. The military should continue to evaluate food preferences of soldiers when they are under stress and in strenuous circumstances and to reformulate or replace products accordingly. Existing food products already in the marketplace should be considered for inclusion when they meet nutritional and sensory needs and stability requirements. Specific foods that are high in needed nutrients, such as potassium in fruits, can be included to formulate rations, in lieu of relying upon vitamin or mineral fortification. The ration is expected to be stable for long periods of time (up to three years) and to retain its sensory quality and nutritional value; the stability of the ration must be monitored carefully by planned analytical testing. Product developers should capitalize on existing and innovative processing technologies for future products and for fortification. MONITORING RATION PERFORMANCE AND USE The ration recommended here was designed with the best available data. Some of the data, however, derive from studies in which the environment or the subjects were substantially different from the ones for which this ration is to be utilized. For example, much of the data on optimizing physical performance come from studies performed with athletes; to extrapolate the conclusions regarding athletes to highly trained soldiers deployed in short combat missions is
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations generally not ideal. The committee believes that further work needs to be conducted to confirm that the current ration provides optimal performance and maintains health or to have the opportunity of improving the ration by making necessary adjustments. Additionally, little is known about food preferences of subjects under such stress. The military should consider conducting studies to test the performance and acceptability of the ration under the real circumstances of combat and under different environments (e.g., cold versus hot versus high altitude) with attention to actual duration of use of such rations. The military should closely monitor the actual use of the ration. This ration was designed for the rigorous operational conditions assumed, specifically, short-term missions to which highly trained male soldiers are deployed. For health reasons, it should not be used as a substitute for other rations when military personnel are in garrison or in other types of extended missions. The committee’s recommendations on adding carbohydrate and salt supplements are critical to maintaining the health and performance of soldiers. They are particularly important for individuals who lose salt in excess, for missions in hot climates, or during strenuous exercise. Due to the stressful circumstances or other factors, some soldiers may not be always aware or knowledgeable of their health status or nutrient requirements. Soldiers required instructions on the use of these carbohydrate and salt supplements and should be reminded of their use at appropriate times. The military should be attentive to the quality of the ration from both a microbiological and a chemical composition standpoint. For some of the nutrients, such as fructose, a change in the recipe (i.e., a substantial increase in fructose) may have adverse gastrointestinal tract effects on a number of individuals. It is critical not only to advise the food manufacturer to carefully follow the formulation of a food as prescribed but also to perform in-house nutrient analysis of the products. Tests to determine the microbiological stability of the products for safety and quality reasons are also indispensable in all food quality control operations. FUTURE NEEDS The committee finds that gaps in knowledge exist and that additional data in the following general areas of investigation should prove particularly beneficial to future development and refinement of an optimal ration for the military operations envisioned: (1) additional knowledge regarding nutrient requirements and food technology issues; (2) deeper understanding of food preferences under high-stress situations; (3) more information on conditions under which the ration is actually used; and (4) development of methods to identify individuals at risk of losing excess electrolytes or developing kidney stones. Specific suggestions for future research needs can be found for each individual nutrient in Chapter 2. The following are specific areas of research that the committee considers of priority
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations to continue the efforts in developing rations to enhance physical and cognitive performance during high-stress, short-term situations. The committee emphasizes the importance of conducting studies under conditions that approximate the combat situations for which the ration is required; in addition, the physical and cognitive performance outcome measurements should be relevant and appropriate for those conditions (e.g., shot pattern tightness, complex reaction time, vigilance rather than objective or self-reported measurements of mood states). Research on Nutrient Requirements Conduct research to determine whether the hypocaloric status of soldiers reported in combat has an effect on physical and cognitive performance measures that are relevant in combat situations. Confirm the effects of high-carbohydrate and high-protein diets on performance under hypocaloric conditions and stress on physical and cognitive performance; the effects of a high-protein diet on muscle loss and immune function should be specifically tested under those scenarios and under various climates (e.g., hot and cold temperatures). Study the potential benefits of carbohydrate supplementation for soldiers under hypocaloric conditions and stress on cognitive and physical performance; to minimize the confounding effects of energy intake, these studies should be conducted at the same energy intake level for all subjects. Conduct further research on the potential benefits of adding specific amino acids in addition to protein when subjects are consuming a hypocaloric diet under the environmental conditions and high-stress situations of combat missions. There is suggestive evidence obtained under significantly different conditions that warrants continuing research, specifically with arginine for immune enhancement and wound healing, and glutamine for intestinal function and immune function. Investigate the potential synergistic effects of a mixture of antioxidants (e.g., vitamin C, vitamin E, and flavonoids) from antioxidant-rich foods and fortified foods on physical performance and immune function in a randomized trial. Before such studies are conducted, valid markers of antioxidant activity that will permit comparison of studies across laboratories are needed. Determine the requirements of certain micronutrients (e.g., vitamins C and E, B vitamins, zinc, selenium, iron, copper) when individuals are consuming a hypocaloric diet under the environmental conditions and high-stress situations of combat missions (e.g., intense physical activity, high energy expenditure and reduced caloric intake, and hot and humid conditions). This would include evaluating the losses of minerals through sweat, urine and feces, as appropriate. This would also include assessing
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Nutrient Composition of Rations for Short-Term, High-Intensity Combat Operations the potential benefits of supplementing some nutrients in maintaining or improving health and performance. Pursue randomized, well-controlled trials to elucidate the risks (e.g., withdrawal effects) and potential benefits (e.g., cognitive performance) of taking selected bioactives that are often consumed in the field, such as creatine; these trials should be conducted under conditions that mimic combat situations. Investigate and document the feasibility of using such rations in emergency disaster, high-stress situations when adequate rations to sustain energy balance may be impossible to provide. Research on Food and Ration Development and Field Use The committee concludes that the US Army Research Institute of Environmental Medicine and the Natick Soldier Center should continue the existing systematic approach to ration development for combat missions. As currently practiced, in addition to the required nutrients, such an approach should incorporate early in the design process issues of palatability and food preferences of end-users. Other critical factors to consider are the required long shelf-life of the rations, nutrient interactions, and packaging considerations. Study the combined effects of intense physical activity, acute stress, and energy deficit on hunger and appetite. Evaluate the acceptability of the assault ration under field conditions to determine percentage eaten and food preferences. The extent of selectively trading and discarding ration items under combat conditions needs to be evaluated by surveys. Monitor the actual use of rations with respect to duration and frequency of use under actual field conditions. Create innovative ways of adding certain nutrients to foods without compromising palatability; specifically, pursue research to improve palatability characteristics of foods with the high concentrations of sodium and potassium recommended. In addition, develop ingredients to hide bitterness qualities of metals and other nutrients. Test the safety and quality of products in the ration throughout their shelf-life. This should include chemical analysis of the recommended nutrients. REFERENCES Anderson GH, Moore SE. 2004. Dietary proteins in the regulation of food intake and body weight in humans. J Nutr 134(4):974S–979S.
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Representative terms from entire chapter: