INTRODUCTION

The U.S. Army Field Feeding System can be tailored to the tactical situation and unit mission in both training and combat environments (AR 30-21, 1990). The cornerstone of field feeding is the military ration. Generally, a ration is the nutritionally adequate food necessary to subsist one person for 1 day. A meal is a specific quantity of food provided for one person during one scheduled serving period. Military rations used for cold-weather field feeding are nutritionally adequate in accordance with the Military Recommended Dietary Allowances (MRDA) (AR 40-25, 1985). Military rations may be wet packed, i.e., they do not required additional water during preparation, or dehydrated and are divided into group feeding rations and individually packaged rations. Although any military ration may be provided to the soldier while operating in cold environments, some rations may be more suitable than others.

MILITARY RECOMMENDED DIETARY ALLOWANCES FOR COLD WEATHER

Military Recommended Dietary Allowances (MRDAs) are the recommended daily nutrient intake levels that should meet the nutritional and physiological requirements of practically all healthy 17- to 50-year old, moderately active military personnel (AR 40-25, 1985) (Table 5-1). The MRDAs are established jointly by all military services, in concurrence with the Food and Nutrition Board of the National Research Council. The 1985 MRDAs are based on the 1980 Recommended Dietary Allowances (RDAs) (NRC, 1980), with the increased requirement of certain nutrients due to the increased physical activity and, therefore, increased energy requirement of military personnel compared to their more sedentary civilian counterparts. The MRDAs are used for evaluating the nutritional adequacy of military rations, ensuring that military personnel maintain their nutritional status, health, and performance in extreme as well as temperate environments. The MRDA are currently being revised to reflect the 1989 RDAs (NRC, 1989).

TABLE 5-1

Military Recommended Dietary Allowances.

The increased energy requirement during cold-weather operations is due to the heavy cold-weather clothing and footgear (the hobbling effect), and increased effort needed for locomotion on snow- or ice-covered terrain (Gray et al 1957; Johnson and Kark, 1947; see Jones and Lee, Chapter 11 in this volume). Energy requirement increases in proportion to the amount of time spent working in the cold; thus, it is dependent on mission. The increased energy allowance does not apply to military personnel stationed in cold climates who are not engaged in field operations.

Even though the MRDAs recommend a minimum of 4,500 kcal/d for military personnel working in the cold, energy requirements for cold-weather field operations are variable and difficult to predict. Studies in which energy expenditure of military personnel working in the cold was measured using stable isotopes showed mean energy expenditures of 4,253 kcal/d (King et al., 1992) and 4,919 kcal/d (Hoyt et al., 1991).

MILITARY RATIONS USED IN COLD WEATHER

Military rations may be wet packed, i.e., they do not required additional water during preparation, or dehydrated and are divided into group feeding rations and individually packaged rations. Although any military ration may be provided to the soldier while operating in cold environments, some rations may be more suitable than others. Freezing of rations and water, and difficulties associated with preparing and serving hot foods, are inherent problems of cold-weather field feeding.

Group Feeding Rations

Group feeding rations are used whenever the opportunity to eat together as a unit is possible. The meals are prepared and served hot to military personnel. Among the group feeding rations, the Tray Pack (T Ration) is the ration most commonly used for cold-weather field feeding because it does not require refrigeration or cooking. The other group feeding rations are: (1) A Ration, which consists of both shelf-stable and perishable food items requiring refrigeration and cooking, and (2) B Ration, which consists of canned and dehydrated food items requiring cooking but no refrigeration. Because of the effects of extreme cold temperatures on the equipment required to maintain and prepare the A and B Rations, these rations are not commonly served during cold-weather field operations.

Tray Pack

The Tray Pack (T Ration) is ready to heat and serve. The ration is thermally processed, pre-prepared, shelf-stable food, packaged in hermetically sealed half-size steamtable metal containers. The containers serve as the package, heating pan, and serving tray. The containers can be heated, unopened, in boiling water for 15–50 minutes (depending on the product) or opened and heated in an oven to an internal temperature of 165°F (74°C). A special hand-held or table-mounted can opener is required to open the T Ration food containers.

The ration consists of 10 breakfast and 10 lunch-dinner menus including an entree, starch, vegetable, and dessert (Table 5-2). The T Ration is augmented with a cold-weather supplement module (Arctic T), which provides additional calories to meet cold-weather energy requirements. The supplement module consists of oatmeal, soup, candies, cookie bars, bread, and additional hot beverages. The Arctic T also contains styrofoam clamshell trays and hot cups with lids to maintain food temperature during serving. The Arctic T Ration provides approximately 2,400 kcal per meal (including approximately 1,000 kcal supplied by the cold-weather supplement module) (NRDEC, 1992).

TABLE 5-2

Menus of Military Rations Used in Cold-Weather Operations.

Individually Packaged Rations

Individually packaged rations are used when the mission or tactical scenario prevents group feeding. These rations provide singular meals that can be consumed hot or cold, but they are more palatable when they are hot. Therefore, individual flameless ration heaters are provided to the soldiers so that the rations can be heated. The chemicals in the heater pad (magnesium and iron) are activated by 2 oz (59.2 ml) of water, and it takes only 10 to 12 minutes for the entree to reach an optimal serving temperature of 140°F (60°C).

Meal, Ready-to-Eat

The standard military operational ration is the Meal, Ready-to-Eat (MRE), which is wet packed. It consists of heat-processed, shelf-stable food components that require no preparation. Twelve menus are available, each containing an entree, crackers, a spread (cheese, peanut butter, or jelly), dessert, candy, and beverage powder (Table 5-2). The water requirement is approximately 23 oz to rehydrate all beverages in one MRE; thus, the water requirement for an entire day subsisting on MREs could be 92 oz. One meal provides 1,300 kcal (15 percent protein, 49 percent carbohydrate, and 36 percent fat) and 1.8 g sodium (NRDEC, 1992). Thus, to meet the cold-weather energy requirement, the soldier requires four MREs (Table 5-3) or three MREs with an energy supplement. An example of an energy supplement commonly provided to soldiers working in the cold is granola bar, beverage powder, pouch bread (shelf-stable, water-activity controlled bread in a pouch), and trail mix.

TABLE 5-3

Approximate Nutritional Content of Rations Used in Cold-Weather Operations.

Ration, Cold Weather

The Ration, Cold Weather (RCW) is a dehydrated ration that can be reconstituted with hot or cold water or consumed dry. This ration was developed to satisfy a Marine Corps requirement in 1983 for their annual deployment of units to Norway for cold-weather training. Subsistence items and rations available at that time were unsatisfactory for three reasons: (1) they were too bulky or heavy; (2) they contained amounts of sodium and protein that were in excess of requirements and added to the metabolic water burden; or (3) their high water content made them susceptible to freezing.

The RCW consists of six menus and contains freeze-dried, cooked entrees and other low-moisture foods, such as granola bars, oatmeal, nut-raisin mix, chicken noodle soup, fruit bars, and crackers (Table 5-2). Several beverage mixes and soup are included in each menu to encourage water consumption. The water requirement is 90 oz per ration, if all components are consumed hydrated; thus the water requirement for an entire day subsisting on RCW could be 90 oz. The ration is lightweight and will not freeze. There are 2 meal bags per ration which provide food for 24 hours. The protein and sodium contents are adequate but are reduced to conserve metabolic water requirements. One ration (two meals) provides 4,500 kcal (8 percent protein, 60 percent carbohydrate, and 32 percent fat) and 5 g sodium, enough food to meet energy and nutrient requirements in cold-weather operations (Table 5-3).

Long-Range Patrol, Improved

The Long-Range Patrol, Improved (LRP I) is a dehydrated, lightweight, freeze-resistant ration which occasionally is used during cold-weather operations. This ration was designed to sustain personnel during initial assault and special operations (one ration per day). When used in cold weather, this ration can be used as a meal (e.g., one per day in conjunction with two group ration meals) or as one complete day's ration (three LRP I meals per day). The LRP I has eight menus, each consisting of an entree, cereal bar, cookie, candy component, and beverage (Table 5-2). The water requirement is 10 to 12 oz for the entree and 16 oz for the beverages; thus, the water requirement for an entire day subsisting on LRP Is could be 84 oz. One ration provides 1,500 kcal (15 percent protein, 50 percent carbohydrate, and 35 percent fat) and 2.5 g sodium (NRDEC, 1992). Three LRP Is would provide enough food to meet cold-weather energy requirements (Table 5-3).

SELECTING A MILITARY RATION FOR COLD-WEATHER OPERATIONS

The selection of military rations for cold-weather operations is influenced by the tactical situation, mission, and logistical support. These factors determine length of operations, how feasible it is to carry the rations, how often resupply would occur, how much water would be available, etc. Thus, ration weight, size, and amount of water required for reconstitution are important considerations. Table 5-4 illustrates how some military rations may be more suitable than others during cold-weather operations. For instance, a daily supply of MREs weighs approximately twice as much as a daily supply of RCW or LRP Is. This difference becomes critical when, due to length of mission, military personnel are required to carry several days' supplies.

TABLE 5-4

Characteristics of Individually Packaged Rations Used in Cold-Weather Operations.

The macronutrient distribution of these rations is similar, except for the percent energy provided by protein. Where most of the rations provide approximately 15 percent of total calories from protein, the RCW provides only 8 percent (NRDEC, 1992). The RCW was designed to be lower in protein than other rations to conserve metabolic water in the cold. Still, the RCW is adequate in protein, providing over 90 percent of its MRDA. Studies conducted by scientists from the U.S. Army Research Institute of Environmental Medicine (USARIEM) have shown similarities among the nutritional intake of soldiers consuming MREs, RCWs, LRP Is, and Arctic Ts during cold-weather field training exercises (Edwards et al., 1991, 1992; King et al., 1992). These studies also showed that even though the soldiers were provided with an adequate supply of rations, they did not consume enough food to meet their energy requirements. Overall ration acceptability was reported at or above ''neutral" score for MREs, RCWs, LRP Is, and Arctic Ts, suggesting that the low intake was not caused by poor acceptability (Edwards et al., 1991, 1992; King et al., 1992).

AUTHOR'S CONCLUSIONS

The Army Field Feeding System provides commanders with a variety of alternatives for cold-weather field feeding; thus, the system can be tailored to tactical situation and unit mission (AR 30-21, 1990). Each feeding modality and ration has intrinsic advantages and disadvantages. For instance, whereas group feeding promotes socialization that increases morale and food intake, it may interfere with military operations. Further, group feeding rations require kitchen equipment and utensils. While wet packed rations are more convenient to use than dehydrated ones, they are heavier, bulkier, and prone to freezing. On the other hand, the dehydrated rations require additional hot water to make them more palatable and increase their consumption.

While the provision of adequate nutrition and hydration to military personnel remains a major problem during cold-weather operations, the commander must consider ration characteristics together with the environmental conditions, unit tactical situation, mission, and logistical support. The final decision should be made carefully to optimize mission accomplishment and military performance. The consequences of poor nutritional intake and dehydration are increased medical problems and decreased unit effectiveness. Command leadership and enforcement of ration consumption and water discipline are crucial to prevent these consequences. Most often, a combination of rations, such as Arctic T breakfast, LRP I lunch, and Arctic T dinner, provides maximum flexibility for the commander and increases ration consumption.

REFERENCES

• AR (Army Regulation) 30-21 1990. See U.S. Department of the Army, 1990.
• AR (Army Regulation) 40-25 1985. See U.S. Departments of the Army, the Navy, and the Air Force, 1985.
• Edwards, J.S.A., and D.E. Roberts 1991. The influence of a calorie supplement on the consumption of the Meal, Ready-to-Eat in a cold environment. Milit. Med. 156:466–471. [PubMed: 1961428]
• Edwards, J.S.A., D.E. Roberts, and S.H. Mutter 1992. Rations for use in a cold environment. J. Wilderness Med. 3:27–47.
• Hoyt, R.W., T.E. Jones, T.P. Stein, G.W. McAnninch, H.R. Lieberman, E.W. Askew, and A. Cymerman 1991. Doubly labeled water measurement of human energy expenditure during strenuous exercise. J. Appl. Physiol. 71:16–22. [PubMed: 1917738]
• King, N., S.H. Muter, D.E. Roberts, E.W. Askew, A.J. Young, T.E. Jones, M.Z. Mays, M.R. Sutherland, J.P. DeLany, B.E. Cheema, and R. Tulley 1992. Nutrition and hydration status of soldiers consuming the 18-Man Arctic Tray Pack Ration Module with either the Meal, Ready-to-Eat or the Long Life Ration Packet during a cold weather field training exercise. Technical Report T4-92. Natick, Mass.: U.S. Army Research Institute of Environmental Medicine.
• King, N., D.E. Roberts, J.S.A. Edwards, R.D. Morizen, and E.W. Askew 1994. Cold-weather field feeding: An overview. Mil. Med. 159(2):121–126. [PubMed: 8202237]
• NRC (National Research Council) 1980. Recommended Dietary Allowances, 9th revised ed. A report of the Committee on Dietary Allowances, Food and Nutrition Board, Division of Biological Sciences, Assembly of Life Sciences. Washington, D.C.: National Academy Press.
• 1989. Recommended Dietary Allowances, 10th ed. A report of the Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition board, Commission on Life Sciences. Washington, D.C.: National Academy Press.
• NRDEC (U.S. Army Natick Research, Development and Engineering Center) 1992. Operational Rations of the Department of Defense. Natick Pamphlet 30-2. Natick, Mass.: U.S. Army Natick Research, Development and Engineering Center.
• U.S. Department of the Army 1990. Army Regulation 30-21. "The Army Field Feeding System." September 24. Washington, D.C.
• U.S. Departments of the Army, the Navy, and the Air Force 1985. Army Regulation 40-25/Naval Command Medical Instruction 10110.1/Air Force Regulation 160-95. "Nutrition Allowances, Standards, and Education." May 15. Washington, D.C.

Footnotes

1

Nancy King, Nutrition Care Division, Brooke Army Medical Center, Fort Sam Houston, TX 78234-6306. Formerly of Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007