11 Mission Nutrition for Combat Effectiveness

Key Points

• Inadequate energy intake and/or dehydration can result in fatigue and impair your performance during combat.
• Disruptions in eating and sleeping due to all-night and high op-tempo missions can affect your overall health.
• Plan to eat before night operations to prevent fatigue.
• Environmental exposures such as heat, cold, and altitude can reduce combat effectiveness if your nutritional and hydration needs aren’t met appropriately.
• Energy and fluid requirements are typically higher than normal during combat and combat-simulated scenarios.

Adequate fueling is essential for operational performance and mission success. Operators of equipment such as Humvees, helicopters, and submarines especially need high-performance fuels to operate effectively. In some instances, fueling options are limited, but it’s critical to meet your energy and fluid requirements whenever possible. This chapter describes fu­eling options when you’re exposed to various environmental and logistical extremes.

Nutritional readiness before missions

Warfighters must be prepared to deploy at any time. Immedi­ately before, they might find themselves in the field or under lockdown on base. The two main nutritional considerations for readiness before missions are optimum glycogen stores and proper hydration.

Timing and composition of pre-mission meals

A pre-mission meal can help ensure adequate glycogen stores and maintain your blood sugar. A carb-rich eating plan (for several days before a mission, if possible) will increase glycogen stored in the liver and muscles and ensure adequate fuel stores.¹ Every Warfighter should know his or her own tolerance for timing of meals, types of snacks, and amounts of food needed to sustain performance. In general, intense physical activities demand a longer waiting period after you eat to allow for digestion and minimize gastrointestinal (GI) distress, as discussed in Chapter 9.

A pre-mission meal should be high in carbohydrates with some fat and protein. Avoid high-fat and high-protein meals because protein and fat digest more slowly than carbohydrates. Carbohydrate beverages and carb/protein drinks are excellent choices if consumed 1–4 hours before the start of a mission. The body digests and absorbs liquids more rapidly than solids, but personal taste and suitability are important in choosing what to consume. Be sure to try any new foods and beverages before deploying to ensure tolerance during missions.

Maintaining nutrition during missions

Rations

Boredom with rations and lack of time to eat contribute to decreased ration intake and weight loss. So, it’s important to consume as much of your field ration as possible to maintain optimal performance and health. Combat rations often are fortified with vitamins and minerals to optimize nutrition, so try to eat at least part of each ration item whenever possible to obtain all the essential nutrients. See Chapter 13 for more information about combat rations.

Limit substitution of non-issue food items for rations or meals since they might lack important nutrients. Save them for snacks to supplement your daily rations. When authorized by your Command, pack high-carbohydrate items such as crackers, dried fruit, trail mixes, and sports bars too. Ex­periment with new foods and timing beforehand—during training—to see what eating patterns and foods suit you best.

Hydration status

Adequate daily fluid intake is critical to maintain optimal operational performance and health. Warfighters’ fluid needs usually are greater than the recommended general guidelines (see Chapter 5) due to their intense training or work­ in extreme environments. Dehydration can affect your mental and physical performance, so stay hydrated with water, including beverages (such as juice, milk, coffee, and tea) and foods (mostly fruits and vegetables; see list in Chapter 5) that contain water.

You’ll also need electrolyte replacement if you’re (1) physically active longer than 3 hours; (2) not getting adequate nutrition; or (3) working in conditions where you sweat a lot, such as humid and hot weather conditions in the field and military exercises in­volving high mobility and strenuous physical work.² In such situations, consume fluid-replacement beverages with carbs and electrolytes (sodium and potassium) during extended missions, as discussed in Chapter 5. A carbohydrate–electrolyte beverage powder is available in rations, but if you use a commercial sports drink instead, choose one with no more than 24g of carbs per 8 oz during missions.

GI complaints

Changes in diet, dehydration, too much fiber, poor sanitary conditions, contaminated food, unfamiliar bacteria, and stress might result in diar­rhea or constipation in the field. Try to ensure adequate hydration at all times and avoid new, non-issue foods whenever possible. See Chapter 14 to learn more about relieving GI distress.

Dietary fiber

Dietary fiber makes food pass through the GI system faster, improves stool bulk and weight, and promotes regularity. Consider a low-fiber diet during extended operations. Many high-fiber foods can cause bloating and gas, especially if you don’t consume them regularly or if you don’t drink enough water. It’s important to gradually add fiber to your diet to prevent GI distress. Test high-fiber foods during training to find out how your system reacts. Avoid all dietary modifications right before a mission or operational scenario.

Caffeine

Caffeine is a stimulant found in energy drinks, coffee, tea, many sodas, some dietary supplements, and a few components of military rations. Research on caffeine shows it positively affects military-relevant tasks such as marksmanship, reaction time, vigilance, and logical reasoning.^3-7 In athletics, caffeine can help reduce perception of fatigue and allow you to sustain your targeted (or intended) intensity for a longer period of time.

Caffeine can increase your alertness and possibly even delay fatigue during extended operations. Caffeine (in moderate doses up to 200 mg) can improve cognitive performance in rested, sleep-deprived, and fatigued individuals.^8-10 However, the effective dose can vary, depending on your habitual caffeine intake and sensitivity to caffeine, and higher doses can cause unwanted side effects such as nausea, anxiousness, insomnia, and restlessness, which can have a negative effect on performance.^8,11

Caffeine-rich beverages and foods are among the most popular forms of nutrition to help Warfighters maintain alertness at night. Sources of caffeine in First Strike Rations and Modular Operational Ration Enhancement include caffeinated chocolate pudding (200 mg), Mocha First Strike Bar (mini; 110 mg) and caffeinated mints and gum (100 mg per piece, 5 pieces per package). In addition, coffee is available in the Meal, Ready-to-Eat (MRE), FSR, and Meal, Cold Weather (MCW) rations (80–100 mg per package).

For more about caffeine and performance, see the Operation Supplement Safety (OPSS) Caffeine & Performance infographic and Tables 11–1 and 11–2 below. Despite its effects on alertness and performance, caffeine shouldn’t be used as a substitute for healthy habits (adequate sleep, regular meals, etc.).

Table 11–1. Caffeine Content of Selected Beverages*

*Except where noted otherwise, caffeine content was obtained from the USDA Food Composition Databases.¹² Actual caffeine content can vary depending on brand and preparation.
**Caffeine content obtained from product’s marketing website or third-party retail website.

Table 11–2. Caffeine Content of Selected Foods and Over-the-Counter Drugs*

*Except where noted otherwise, caffeine content was obtained from the USDA Food Composition Databases. ¹² Actual caffeine content can vary depending on brand and preparation.
**Caffeine content obtained from product’s marketing website or third-party retail website.

Sustained night operations

Night exercises require acute cognitive awareness and the ability to react quickly to sudden and potential compromised situations. Missions include both Sustained Operations (SUSOPS) and Con­tinuous Operations (CONOPS), which frequently can result in fatigue and sleep deprivation. SUSOPS—work periods of 24 hours or more—usually result in physical and mental fatigue as well as sleep loss. In contrast, CONOPS involve periods of uninterrupted activity of “normal shift length” followed by “normal” sleep, but not always sufficient to recover or prepare for SUSOPS.^13-14

Under-fueling while exposed to these strenuous circumstances can lead to weight loss, fatigue, and mental impairments, including confusion, depression, and loss of vigilance.¹³ Nutritional interventions can partially offset the detrimental effects of fatigue and sleep deprivation on physical and mental perfor­mance. You need high-carb meals and snacks to maintain muscle glyco­gen stores and blood glucose. If you fail to fuel properly during sustained missions, your blood glucose levels will fall, resulting in hypoglycemia (low blood sugar) and a decline in performance. Symptoms of hypoglycemia include headache, dizziness, blurred vision, weakness, fatigue, sweating, confusion, and unconsciousness.

Missions in the heat

Repetitive movement along difficult terrain with heavy gear, such as during land-warfare operations, is strenuous under any environmental condition, but it’s particularly grueling with extreme heat and humidity. Land-warfare scenarios in which Warfighters carry heavy loads or injured com­rades increase overall effort, energy expenditure, and fluid and electrolyte needs. The major concerns during operations in a warm or hot environment are fluid and electrolyte balance. Working or exercising in the heat worsens water and electrolyte loss through sweating. The amounts of sweat and fluid lost depend on:

• Environmental temperature and humidity
• Work rate
• Fitness level and acclimatization
• Volume and rate of fluid replacement
• Genetics

When the same task carried out in a more neutral-temperature environment is per­formed in a hot environment, energy requirements increase slightly due to the increased work of maintaining thermal balance.¹ If you’re acclimated to heat, you likely won’t need to increase your calories. However, working in the heat might decrease your appetite or alter your food preferences, so it’s important to monitor your food intake and any changes in body weight.¹⁵

Fluids—Drink early and often

High work rates in hot, humid surroundings can significantly increase fluid and electrolyte losses. Losses of 1–2 quarts (32–64 fl oz) per hour or even more are likely when Warfighters wear special clothing such as chemical protective gear or body armor.¹⁵ Your risk of performance mishaps is greater when you start any operation without being adequately hydrated. In addition, failure to replace fluids lost from sweating will result in dehydration and possible heat injury. When engaging in light to moderate activity in a temperate climate (under 86°F), you should aim to drink 2–5 quarts of fluids per day, but when working in the heat, your daily fluid needs can double.² Fluid-replacement beverages are most useful for rehydration. If it’s available, fruit also provides some carbs, electrolytes, and fluid to help hydration.

Don’t rely on thirst as a guideline to drink. By relying solely on thirst, your hydration can lag several hours behind fluid needs.¹⁶ Try to set a pre-determined drinking schedule to ensure you’re consuming enough fluids. Make sure to drink some type of beverage (water, juice, milk, iced tea, or sports drink) with all meals and snacks too.

Although such “forced drinking” is recommended during training and missions in a warm environment to ensure adequate fluid replacement for performance, drinking too much water can result in hyponatremia (as discussed in Chapter 5). Symptoms of hyponatremia include headache, vomiting, fatigue, confusion, and disorientation. Do not drink more than 1.5 quarts (48 fl oz) of water per hour or 12 quarts (384 fl oz) per day.¹⁶

Electrolyte balance

Excessive loss of electrolytes (sodium and potassium) from sweating can lead to other severe medical problems. You can help minimize electrolyte losses if you stay in excel­lent physical condition. To maintain electrolyte balance, you might need to consume snacks that contain sodium and potassium, fluids with electrolytes, or electro­lytes in the form of gels or chews during and after mis­sions. Dried fruits are optimal food choices for potassium. For ex­ample, a small box of raisins (1.5 oz) provides 320 mg of potassium. Adding salt to foods (½ teaspoon provides 1,200 mg) or including sodium-rich foods in your diet will help retain water and avoid a sodium deficit. MREs provide sodium within the food components and in the salt packet.¹⁶ Sodium is the most critical electrolyte for maintaining fluid balance. The Military Dietary Reference Intake for sodium is <2300 mg for men and women.² Adequate sodium intake should offset hyponatremia.

Missions in the cold

Exposure to a cold environment seriously challenges the human body. Blood vessels tighten to conserve heat, and shivering gener­ates heat and guards against hypothermia (a dangerously low core body temperature). Side effects of these responses are increases in urine out­put and energy metabolism.

Energy intake

Energy requirements can increase 10–40% during cold-weather operations as compared to warm-weather operations.¹⁷ Factors that can increase your calorie needs include:

• Added exertion due to wearing heavy gear
• Shivering to maintain body temperature
• Greater exertion traveling over snow and icy terrain
• Increased activity to keep warm

Energy expenditure for Warfighters during periods of physical exertion in the cold might range 4,200–4,600 calories per day, with some situations requiring as much as 6,000 calories per day.¹⁷ A high-carb eating plan can provide the carbohydrates you need to replenish the glycogen your body uses to maintain core temperature. The high-calorie needs of cold weather operations can be difficult to meet. Both fat and carbs are significant energy sources, so you might need an eating plan that provides 35% of the energy as fat. Consume 3–4 standard MREs or 3 MCW/LRP rations per day to meet your energy needs.

Supplementing regular meals with frequent snacks between meals and before bed also can help you meet your calorie needs. High-carb snacks, many of which can be stored in your pockets for portable access, include:

• Granola or power bars
• Oatmeal cookies
• Hot or cold protein or carb beverage
• Bagel with jam
• Pretzels
• Trail mix
• Dried or fresh fruit
• Crackers with hard cheese
• Popcorn, corn chips, or tortilla chips

Keep in mind that the increase in energy requirements doesn’t apply to Warfighters located in cold-climate regions unless they are actually exposed to outdoor temperatures.¹⁷

Fluid status

Becoming dehydrated in cold environments is easy because of cold-induced increase in urine output, increased fluid losses through breathing, involuntary reduction in fluid intake, and sweating. Since dehydration decreases your performance and might lead to various medical prob­lems, it’s crucial to drink plenty of fluids and monitor your hydration, as discussed in Chapter 5. Fluid needs depend on physical activity level, but most Warfighters require 3–6 quarts (96–192 fl oz) per day for adequate hydration.¹⁷ Try these tips to help maintain your fluid status.

• Drink fluids (water, juice, tea, sports drinks, and coffee) with meals.
• Force yourself to drink 16–32 fl oz of warm fluid at hourly intervals.
• Avoid alcoholic beverages because alcohol tends to increase heat and urine losses.
• Drink beverages with carbs to increase your energy intake.
• Don’t eat snow without first melting and purifying it.

Vitamin and mineral needs

Your requirements for some vitamins (for example, thiamin) and minerals (such as magnesium or zinc) are greater when you’re work­ing in the cold due to increases in energy metabolism or urinary losses.¹⁸ People who are deficient in iron, copper, or zinc sometimes have difficulty regulating their body temperature. In most cases, you can meet your energy (calorie), vitamin, and mineral requirements by eating all ration components.

Missions at altitude

Ascent to altitude and flying can cause a variety of disturbances and increased oxidative stress, so adequate nutrition is crucial to maintain performance. The major nu­tritional concerns at altitude are:

• Weight loss
• Carb intake
• Dehydration

Weight loss

At altitudes greater than 10,000 feet, energy needs greatly increase (by as much as 25%), especially for Warfighters performing extremely strenuous activities.¹⁹ Virtually all people who go to high altitudes experience loss of weight and lean body mass due to greater energy needs, reduced food intake, loss of body fluids from increased breathing, decreased fluid intake, decreased absorption of nutrients, and GI symptoms (nausea, vomiting, and decreased appetite) related to Acute Mountain Sickness (AMS).¹ Over a period of several weeks or longer, bodyweight loss of approximately 5% or less is typical and usually won’t affect the performance of most tasks.²⁰

The only way to minimize weight loss is to be vigilant about your energy intake.

Carbohydrate intake

High-carb foods are the preferred energy source at altitude and in flight because they:

• Replete glycogen stores
• Provide the most efficient energy source
• Can delay the progression or severity of AMS and reduce its symptoms (nausea, vomiting, and headache)
• Maintain blood glucose

During strenuous activity, long flights, and recovery, eat high-carb snacks between meals and drink beverages that contain carbs to help meet your carbohydrate goals. Warfighters at altitude should aim to consume a minimum of 400 grams of carbs per day.²⁰

Dehydration

Exposure to high altitude increases your loss of water, resulting in significant risk of dehydra­tion, cold injury, and AMS. Factors that cause dehydration at altitude include:

• Greater respiratory losses due to increased ventilation (breathing)
• Increased urine output associated with altitude and cold temperatures
• Failure to drink water
• Limited access to water

Don’t over-exercise before a flight because strenuous exer­cise can deplete body water, which might be difficult to replace quickly. Re­cent illness (including AMS), fever, diarrhea, or vomiting also will greatly affect your degree of dehydration.

Warfighters at altitude should follow the same guidance for fluid intake as for those in hot environments.²⁰ Maintain a drinking schedule and monitor your hydration status (see Chapter 5) daily to avoid AMS. Take regular sips of water before you feel thirsty to help prevent dehydration as well.

Missions in water and at depth

As with exposure to altitude and cold environments, water operations (espe­cially cold-water operations such as diving) are associated with greater energy expenditure and fluid losses.

Energy intake

When working at the same rate in water as on land, the energy expen­diture to accomplish the same task is greater. The reasons for this increased energy expenditure during water operations include:

• Greater resistance offered by water
• Decreased efficiency of movement when thermal protective clothing is worn

Your body uses glycogen stores rapidly when you’re performing hard work in cold water. It’s important to replace these stores between operations to prevent performance decrements. Increasing carb intake before an anticipated dive has been shown to improve and extend exercise performance during prolonged dives.

Fluid intake

Immersion in water alone doesn’t significantly increase hydration needs. However, water depth and water temperature do affect hydration. Since immersion dulls the thirst response, voluntary water intake might decrease.²¹ Without adequate hydration, a diver can quickly become dehydrat­ed and suffer performance decrements, so it’s important to consume fluids even when you aren’t thirsty.