19.3 Nutrition & Performance
Key Takeaways
- Carbohydrates and protein each provide four calories per gram; fats provide nine calories per gram.
- General macronutrient recommendations are 45-65 percent of calories from carbohydrates, 10-35 percent from protein, and 20-35 percent from fats, with saturated fats under 10 percent of daily calories.
- The optimal post-recovery composition is a four-to-one carbohydrate to protein ratio.
- The Dietary Guidelines recommend adults limit sodium to 2,300 milligrams per day, and at-risk groups to about 1,500 milligrams.
- Total daily water consumption is generally 2.7 liters per day for women and 3.7 liters per day for men, and dehydration occurs with fluid losses greater than two percent of body weight.
Energy Balance
"Airmen are responsible for being mission ready at all times and must recognize that nutrition plays an important role in maintaining good health and performance." Calories from food and beverages need to be balanced with calories burned through metabolism and physical activity.
Estimated calorie needs by age, sex, and physical activity level:
| Group | Range |
|---|---|
| Adult women | 1,600 to 2,400 calories per day |
| Adult men | 2,000 to 3,000 calories per day |
Within each category, the low end is for sedentary individuals and the high end is for active individuals.
A healthy eating pattern includes a variety of vegetables, fruits, whole grains, fat-free or low-fat dairy, proteins, and healthy fats.
AFH 1 recommends the same goal-setting framework used in Chapter 13: "It is helpful to make SMART goals when trying to target these areas." Its examples are worth noting because they show the level of specificity expected: "I will exercise (bike or jog at a moderate heartrate) for 30 minutes, 5 days a week, for one month starting today" and "I will reduce my fast food consumption to one (non-supersized) meal, one time per week, for two months starting today."
The health risk note: being overweight or obese increases the risk of high blood pressure, high blood cholesterol, heart disease, stroke, Type 2 diabetes, arthritis, breathing problems, and some cancers.
Food for Fuel
Carbohydrates can be digested relatively quickly and turned to energy readily available within 30 to 60 minutes. After a workout, a snack or light meal may help replenish carbohydrates burned during exercise and convert them into energy storage (glycogen), and adding protein helps rebuild muscle fibers worked during exercise.
The post-recovery ratio is a reliable item:
"An optimal composition of a post recovery beverage or snack is a four-to-one carbohydrate to protein ratio" — for every four grams of carbohydrate, one gram of protein.
AFH 1's example: an eight-ounce glass of chocolate milk contains about 29 grams of carbohydrates and eight grams of protein, which serves as a great post-recovery replenishment.
Simple healthy snack ideas: low-fat yogurt, nuts and dried fruit, string cheese, and fruit bars.
Micronutrients and Macronutrients
Micronutrients include vitamins, minerals, trace elements, amino acids, and other essential nutrients, required in very small amounts and important for normal function. Eating micronutrient-rich foods promotes healthy brain, heart, blood, and metabolism functions and can prevent micronutrient deficiency disorders.
Macronutrients "make up the bulk of the diet, supply energy, and provide many essential nutrients."
The Calorie-per-Gram Values
| Macronutrient | Calories per gram | Recommended share of total calories |
|---|---|---|
| Carbohydrates | 4 | 45–65 percent |
| Protein | 4 | 10–35 percent (0.8–1.2 grams per kilogram of body weight) |
| Fats | 9 | 20–35 percent |
Four, four, nine. Fat is more than twice as calorie-dense as either of the others, and that single fact answers most macronutrient items.
Carbohydrates
"Carbohydrates are the primary fuel source used during exercise," and an appropriate amount maintains glycogen stores for energy reserve.
| Type | Behavior | Sources |
|---|---|---|
| Simple | Increase blood glucose levels rapidly rather than gradually | Table sugar, brown sugar, corn syrup, honey, fruit drinks, soft drinks, and candy — often in packaged or processed foods |
| Complex | Increase blood glucose levels slowly over a longer period, providing a more sustainable source of energy | Fruits, breads, cereals, grains, milk, and starchy vegetables (potatoes, corn, peas, squash) |
An estimated serving size is about the size of the palm of your hand.
Fiber: found in oatmeal, oat bran, nuts and seeds, legumes, whole wheat bread, barley, brown rice, and most vegetables and fruits. The average American consumes 12–15 grams per day, whereas the recommended total intake is 20–35 grams per day to aid digestion and help balance the absorption of sugar into the bloodstream.
Protein
Used for tissue maintenance, replacement, function, and growth of muscles. "If our body is not getting enough calories from dietary sources or tissue stores, protein may be used for energy."
Sources: meats, poultry, fish, legumes, tofu, eggs, nuts, seeds, milk, milk products, and grains. Focus on lean meats and low-fat milk products to reduce saturated fats.
"The recommended serving size of meat is the size of a deck of cards and contains about 21 grams of protein."
Fats
Fats "are a major energy source and help our bodies maintain temperature and protect organs from trauma." Sources: oils, high-fat cuts of meat, baked sweets, whole-fat milk and cream, butter, cheeses, nuts and seeds, avocados, and fish.
| Type | Health effect and sources |
|---|---|
| Trans fats | Linked to coronary heart disease; intake should be kept as low as possible. Found in small amounts in fatty parts of meat and milk products and in foods containing partially hydrogenated oils — frozen pizzas, frozen pies, cookies, margarine spreads, and other processed foods. Typically made from vegetable oils through hydrogenation |
| Saturated fats | Linked to coronary heart disease; should make up less than 10 percent of daily calories. Usually solid at room temperature — high-fat cheeses, high-fat cuts of meat, whole-fat milk, cream, butter, ice cream, and palm and coconut oils |
| Unsaturated fats | Can reduce risk for heart disease and improve high-density lipoprotein (good cholesterol) levels. Typically liquid at room temperature, including monounsaturated and polyunsaturated. From plant sources — canola oil, olive oil, nuts, seeds, flaxseed, avocado — and fish such as trout, herring, and salmon |
Solid at room temperature = saturated; liquid = unsaturated. That is the fastest discriminator, and less than 10 percent of daily calories is the saturated-fat ceiling to memorize.
Sodium
Sodium is a necessary element, but "high sodium intake raises blood pressure which is a major risk factor for the nation's leading cause of death — heart disease."
| Figure | Value |
|---|---|
| Average American daily consumption | About 3,400 milligrams |
| Dietary Guidelines recommendation for adults | 2,300 milligrams per day — about one teaspoon of table salt |
| "At-risk" groups — those with high blood pressure, diabetes, or kidney disease | About 1,500 milligrams per day |
3,400 actual, 2,300 recommended, 1,500 for at-risk. The best way to keep sodium low is to eat whole foods — fresh or frozen fruits and vegetables, lean and unprocessed poultry and fish, unsalted nuts, whole grains, and low-fat dairy.
Supplements
Supplements may include vitamins, minerals, herbs, botanicals, amino acids, or other substances sold as pills, powders, bars, packs, gels, drinks, or shakes.
The warning is specific and testable: "bodybuilding, performance enhancement, and weight loss products most likely contain undeclared ingredients that may be presented as proprietary blends or delivery systems on the label. These blends do not specify the amount of each ingredient and increase the risk of overdosing on ingredients, such as creatine or caffeine."
Two rules follow:
- "The Food and Drug Administration does not test supplements before they are sold."
- "Look for third party verification/certification labels before purchasing."
"Airmen on flying status must consult with their flight surgeon before taking supplements; however, all Airmen are encouraged to discuss supplement use with their healthcare provider."
Hydration
"The body is made up of about 60 percent water." Water maintains fluid balance, transports nutrients, regulates body temperature, and digests food.
| Figure | Value |
|---|---|
| Total daily water consumption — women | 2.7 liters per day |
| Total daily water consumption — men | 3.7 liters per day |
| Dehydration threshold | Fluid losses greater than two percent of body weight |
| Over-hydration limits | No more than 6 cups an hour and 48 cups a day |
Dehydration increases risk for cognitive and mental performance problems, heat illness, exhaustion, and stroke. But over-hydration is also dangerous, producing chills, vomiting, dizziness, disorientation, altered mental status, fatigue, headache, and even death. "The key with fluid intake is to replace losses and monitor signs and symptoms of under/over hydration."
What Does and Does Not Hydrate
| Beverage | AFH 1's verdict |
|---|---|
| Water | Generally best for remaining hydrated |
| Sports drinks | May be preferred during prolonged exercise or physical exertion to replace electrolytes and carbohydrates; contain carbohydrates, sodium, and potassium, which have been shown to improve exercise performance |
| Caffeine | "Caffeine does not hydrate." Used in moderation has been shown to improve cognitive performance. A cup of coffee typically has 100 milligrams. Large doses — roughly 400–500 milligrams at one time — can result in "caffeine intoxication," leading to nausea, vomiting, agitation, nervousness, headache, electrolyte imbalances, or worse life-threatening symptoms |
| Energy drinks | "Energy drinks are not meant to hydrate." Their effect on athletic performance is inconsistent, and they carry warnings due to stimulants such as caffeine, green tea extract, guarana seed extract, yerba mate, acacia rigidula, taurine, ginseng, or other proprietary blends, which can contain novel, untested ingredients |
| Alcohol | "Alcohol does not hydrate." The Dietary Guidelines advise one drink per day for women and two per day for men. Serving sizes: beer 12 ounces, wine five ounces, 80-proof distilled spirits 1.5 ounces. The average serving has about 150 calories with no nutritional value |
Three beverages that do not hydrate — caffeine, energy drinks, and alcohol — and water, then sports drinks for prolonged exertion, are the pairings the exam tests.
The alcohol serving sizes (12 / 5 / 1.5 ounces) and the 100-milligram cup of coffee versus the 400–500 milligram intoxication threshold are the two numeric sets most likely to appear. Excessive alcohol may increase risk for high blood pressure, liver cirrhosis, and several forms of cancer, and may lead to excess weight gain, chronic diseases, osteoporosis, stress injuries, and impaired short- and long-term cognitive function.
How many calories per gram do carbohydrates, protein, and fats each provide?
What does AFH 1 identify as the optimal composition of a post-recovery beverage or snack?
Which statement about hydration matches AFH 1?