Eating well, in combination with participating in a regular exercise program, is a positive step you can take to prevent and even reverse some diseases. Though nutrition is a broad science, this chapter focuses on some of the basics, along with how to make healthy choices in your daily food intake and how those choices can influence your ability to be active.
Too often, people associate nutrition and diet with restriction and unappealing options (note that the word “diet” refers to what you eat, not a particular weight loss plan). This chapter presents a positive view of nutrition and offers suggestions for taking control of your diet to improve how you feel. By providing your body with needed calories and nutrients, you will fully fuel your body for physical activity and exercise, as well as for competition if you are so inclined. Just as a car needs quality fuel to run smoothly, your body needs a balance of nutrients to function optimally.
The Dietary Guidelines for Americans, published jointly by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, provides general guidance regarding nutrition for people 2 years of age and older. The Dietary Guidelines provides advice about how good dietary practices can promote health and prevent chronic disease.
The Dietary Guidelines for Americans includes the following five guidelines to promote healthy eating (32):
1. Follow a healthy eating pattern across the lifespan.
2. Focus on variety, nutrient density, and amount.
3. Limit calories from added sugars and saturated fats and reduce sodium intake.
4. Shift to healthier food and beverage choices.
5. Support healthy eating patterns for all.
Key recommendations from these Guidelines include following a healthy eating pattern that accounts for all foods and beverages within an appropriate calorie level (32).
A healthy eating pattern includes the following:
· A variety of vegetables from all of the subgroups—dark green, red and orange, legumes (beans and peas), starchy, and other
· Fruits, especially whole fruits
· Grains, at least half of which are whole grains
· Fat-free or low-fat dairy, including milk, yogurt, cheese, and fortified soy beverages
· A variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), nuts, seeds, and soy products
A healthy eating pattern limits the following:
· Saturated fats and trans fats, added sugars, and sodium.
o Consume less than 10 percent of calories per day from added sugars.
o Consume less than 10 percent of calories per day from saturated fats.
o Consume less than 2,300 milligrams (mg) per day of sodium.
· If alcohol is consumed, it should be consumed in moderation—up to one drink per day for women and up to two drinks per day for men—and only by adults of legal drinking age.
These Guidelines are an excellent place to start on the path to a healthier diet. The next step is to look at the nutrients and distribution you require to meet your energy needs.
People of all ages can benefit from healthy foods.
Nutrition and Overall Health
Researchers of nearly all chronic diseases have studied the role of nutrition. (The term chronic is used to refer to diseases that often begin at a younger age and develop over time.) Six of the top 13 causes of death are related to poor nutrition and inactivity. By rank, these are heart disease (number 1), cancer (2), stroke (4), type 2 diabetes (6), chronic liver disease or cirrhosis (12), and high blood pressure (13) (20). Obesity is related to many of these causes of death; and although some have a genetic component, most are related to poor nutrition and lack of exercise, both of which are lifestyle habits.
Chronic diseases resulting from poor nutrition also lead to other disabilities, resulting in further loss of independence. For example, type 2 diabetes is one of the leading causes of blindness and amputation (22). Hip fractures are typically a result of osteoporosis, and people who suffer from a hip fracture are more likely to die within one year of their fracture or require long-term care than people who do not suffer a hip fracture (23). Approximately 69 percent of people who have a first heart attack, 77 percent of those who have a first stroke, and 74 percent of those with congestive heart failure have blood pressure higher than 140/90 mmHg (i.e., hypertension) (4). Obesity is an epidemic, with about a third of adults in the United States considered obese (8). Furthermore, about 17 percent of American children and teenagers (2 to 19 years of age) are considered obese (24).
Researchers have reported that unhealthy eating and sedentary behavior cause around 400,000 deaths per year in the United States (21). Because most Americans consume diets too high in total fat, trans fat, saturated fat, sodium, and sugar, and too low in whole grains, fruits, vegetables, and fiber, poor health and death are often related to poor nutrition. The combination of unhealthy diets and inactivity is the leading cause of death in the United States, above tobacco and alcohol use, and far above drug use and motor vehicle accidents (18). In addition, the health care costs of poor nutrition and inactivity are astronomical. Healthier diets could save billions of dollars in medical costs per year and also prevent lost productivity and, most important, loss of life.
Good nutrition and physical activity are the two most beneficial “medicines” you can use to prevent disease and live a good-quality life. Take control! You owe it to yourself to treat your body well.
Determining Calorie Needs
Because total calorie requirements are addressed throughout this chapter, this section explains the factors that influence your daily caloric needs and shows you how to estimate the number of calories you need. Total energy expenditure (TEE) is the total number of calories your body needs on a daily basis and is determined by the following:
· Your basal metabolic rate (BMR)
· The thermic effect of food (also known as dietary-induced thermogenesis)
· The thermic effect of your physical activity
Basal metabolic rate is defined as the energy required to maintain your body at rest (e.g., breathing, circulation). To precisely determine your BMR, you would need to fast from 8 to 12 hours and then undergo a laboratory test in which you sit quietly for about 30 minutes while the air you exhale is analyzed. This test determines how many calories you are burning at rest. Basal metabolic rate is 60 to 75 percent of TEE. Typically, the larger and more muscular a person is, the higher the BMR is.
The thermic effect of food is the energy required to digest and absorb food. The thermic effect of food is measured similarly to BMR, although the measurement time is usually about 4 hours after you have consumed a meal. The thermic effect of food is 10 to 15 percent of your TEE.
The thermic effect of activity is the amount of energy required for physical activity. It can be measured in a laboratory when you are exercising on a stationary bike or treadmill. The thermic effect of activity is the most variable of the three major components of TEE because it can be as low as 15 percent for sedentary people and as high as 80 percent for athletes who train 6 to 8 hours per day.
One other component of TEE that plays a role is nonexercise activity thermogenesis (NEAT), which is energy expended in unplanned physical activity. Nonexercise activity thermogenesis is characterized by any unplanned physical activity that is not exercise but is more than just sitting still. This can include taking the stairs instead of the elevator, sitting on a balance ball at your desk, parking farther from your destination in a parking lot, fidgeting, and other calorie-burning activities. By figuring out BMR, thermic effect of food, thermic effect of physical activity, and NEAT, an estimate can be made of how many total calories a person would need in a single day, or the individual’s TEE.
What is a calorie?
A calorie is defined as the heat required to raise the temperature of 1 gram of water 1 degree Celsius. Because this is a relatively small amount, scientists use the larger unit Calories (uppercase C), also called a kilocalorie (abbreviated as kcal). The Calorie, or kilocalorie, is equal to 1,000 calories. Food labels in the United States display Calories, or kilocalories. This is all pretty technical and does not reflect typical usage in everyday language. In this book, the word “calories” refers to Calories, or kilocalories (i.e., 1,000 calories), which is common usage.
Although determining your energy needs in a laboratory is precise, you do not need to go to that expense to estimate the number of calories you use. Simpler yet less precise methods of estimation require first calculating your BMR based on your age, sex, height, and weight (13, 19) and then adding in the thermic effects of food and of activity, but this method can be rather time-consuming. For general purposes, the easiest way requires some simple math that allows you to quickly estimate your energy needs. Keep in mind that this method, although the simplest, is the least accurate and should be used only as a rough estimation. See table 3.1 for the estimated daily caloric intake needed to maintain your current weight (34). To calculate your needed daily calorie intake, look at the first column, then find the activity level that best represents your current status. If you know your body weight in pounds, multiply that number by the estimated number of calories per pound in the second column; if you know your weight in kilograms, look at the third column in the table.
Take a moment to do this calculation based on your body weight and activity level. Keep in mind that your final estimate is just that—an estimate. Your actual daily calorie needs may vary somewhat, but this provides an approximate starting point. To maintain your body weight, this is about how many calories you should consume. To lose or gain weight, you will need to adjust your food intake accordingly.
Determining Nutrient Needs
Nutrients include carbohydrates, proteins, fats, vitamins, minerals, and water. The first three—carbohydrates, proteins, and fats—are found in larger (“macro”) quantities in the body and thus are referred to as macronutrients. Vitamins and minerals are found in smaller (“micro”) amounts and are referred to as micronutrients.
Macronutrients (carbohydrates, proteins, and fats) provide energy for daily activities and during exercise, recreational activity, and sport training. They provide slightly different numbers of calories per gram, as follows:
· Carbohydrates provide about 4 calories per gram.
· Proteins provide about 4 calories per gram.
· Fats provide about 9 calories per gram.
These values show clearly that on a gram per gram basis, fat is much denser with regard to calories than carbohydrate or protein. This is the reason a food high in fat provides more calories than a food lower in fat. Chapter 18 provides additional information on the macronutrients as they pertain to weight management. Although alcohol is not a required nutrient, it has its own unique calorie content of 7 calories per gram.
Although some diets (e.g., the Atkins diet) seem to suggest that carbohydrates are the villain when it comes to weight management, carbohydrates are actually vital for the optimal functioning of your body. For example, your brain and central nervous system rely on carbohydrate or glucose in the blood for energy. Carbohydrates are also an important source of energy during physical activity. Without sufficient carbohydrate in your diet, you will not be able to fully enjoy a vigorous workout or competition because your body will not have the fuel it needs to perform.
Carbohydrates exist in the form of sugars, starches, and fiber. Sugars are naturally found in items such as fruit and milk products. Sugar is also added to various products for flavor and taste. Cutting down on products with added sugar is recommended (e.g., candy, nondiet soda, and fruit drinks). These are rather obvious, but checking food labels can reveal added sugars that aren’t as obvious. When searching for added sugars in foods, first check the ingredients list. Added sugars can be identified by many different names, including brown sugar, corn sweetener, corn syrup, dextrose, high-fructose corn syrup, glucose, honey, lactose, maltose, malt syrup, molasses, and sucrose. Be especially careful when these items are listed among the first few ingredients on the food label because components are listed in the order of predominance by weight (31). Based on the 2015 Dietary Guidelines for Americans, the recommendation is to limit calories from added sugars to 10 percent per day (30, 32).
Focusing on fruits, vegetables, and whole-grain products maximizes the health benefits of carbohydrates. Starches are a more complex form of carbohydrate that the body can use for energy and are found in products such as vegetables, dried beans, and grains. Starches are different from sugars because they are chemically composed of long chains of sugars linked together. Consumption of whole grains can help prevent cardiovascular disease, type 2 diabetes, and other chronic diseases mainly because they are high in vitamins and minerals, as well as antioxidants (15, 25). More information on disease prevention appears in part IV of this book.
The third category of carbohydrate—fiber—includes parts of food that the body cannot break down and absorb. Sources of fiber include vegetables, fruits, and whole grains. Consuming higher-fiber foods promotes greater feelings of fullness as well as bowel health. Higher-fiber diets have been found to reduce the risk of diabetes, colon cancer, and obesity (32). Table 3.2 provides examples of good sources of carbohydrates, including the contribution made by fiber (29).
Approximately 45 to 65 percent of your calorie intake should be from carbohydrates (10). This is a relatively wide range to account for the variety of nutritional approaches while avoiding deficiencies or adverse health consequences. Out of this 45 to 65 percent, strive to consume a variety of these types of carbohydrates. Typical diets tend to over consume the simple sugars and under consume starches and fiber. The Daily Value listed on food labels (see the full discussion later in this chapter) is based on 60 percent of the calorie intake. If you are active, or if you are a competitive athlete, keeping your carbohydrate intake near the upper end of this range provides sufficient fuel for your working muscles. Now that you know about how many calories you need per day, as figured from table 3.1, you can determine how much carbohydrate is recommended. For example, for someone who needs 2,500 calories per day, approximately 1,125 to 1,625 calories should be from carbohydrate. This would be calculated as follows:
2,500 calories per day × 0.45 (45%) = 1,125 calories from carbohydrate
2,500 calories per day × 0.65 (65%) = 1,625 calories from carbohydrate
To determine the number of grams of carbohydrate you need, recall that each gram of carbohydrate supplies 4 calories. Simply take the number of calories from carbohydrate and divide by 4 to determine how many grams you need:
1,125 calories / 4 calories per gram = 281 grams from carbohydrate
1,625 calories / 4 calories per gram = 406 grams from carbohydrate
Reading Food Labels
Food labels are important windows of information for products that have them (fresh produce does not). Because there is not enough room to place all the nutrient information on a food label, the label provides only a quick look at the nutrient content. Reading labels, however, can be confusing; the following clarifies the information that labels provide. See figure 3.1 for an example of a food label (33).
Figure 3.1 Sample food label.
Source: U.S. Department of Health and Human Services.
Serving size is usually the first item listed on a food label. Serving sizes are standardized for similar foods. Pay close attention to the serving size, because in some cases, food companies package items in a set of two or more (i.e., the serving size is half of the total amount in the package). Consider a regular-size bag of microwave popcorn. If you eat the whole bag, you have consumed two or three servings of popcorn! Some products list values per serving as well as per package. Paying attention to the serving size helps you track your calorie intake and avoid overeating and gaining weight over time.
Calories and Calories From Fat
You should always check the total number of calories provided in a food item, as well as the total number of calories from fat. Paying attention to serving size is key to determining your overall calorie intake of each food item. As a quick guide to calorie intake, consider the following (31):
· A food item providing 40 calories per serving is considered “low calorie.”
· A food item providing 100 calories per serving is considered “moderate calorie.”
· A food item providing 400 calories or more per serving is considered “high calorie.”
Throughout the course of a typical day, you will likely consume food items in various categories. As long as you keep an eye on the total calories you consume over the course of the day, you will be able to remain in energy balance (i.e., your consumed calories will match the number of calories you expend).
Percent Daily Value
Another item to pay attention to on a food label is the “% Daily Value” (%DV) listed for certain nutrients on all food labels. These values are based on a 2,000-calorie diet. Although this caloric intake might not be a direct match of the calories you need on a daily basis, it does provide general guidance and covers a wide range of people. Daily value reflect recommended levels of intake. For some nutrients (e.g., total fat, saturated fat, cholesterol, and sodium), it is better to aim to consume less than the recommended amount; however, for others, such as total carbohydrate and dietary fiber, it is important to try to consume at least the recommended amount. In general, a %DV of less than 5 percent is considered low, and 20 percent or greater is considered high (31).
When looking at the section of the label focused on fat, note that both saturated and trans fats are listed. You should restrict trans fats as much as possible from your diet and consume no more than 10 percent of total calorie intake in the form of saturated fat. Similarly, keeping cholesterol and sodium levels in check is important. For carbohydrate, the subcategories of dietary fiber, sugars, and added sugars are listed. Limit amounts of added sugars. You should try to increase, rather than limit, your intake of dietary fiber.
Proteins are made of small units called amino acids, which are considered the building blocks of the body. Proteins promote muscle growth and are required for many body functions, including assistance with chemical reactions and hormones. Even though proteins can provide 4 calories per gram, you typically do not use protein for energy unless you are deficient in your intake of carbohydrate or fat. This is so the protein you consume can be used to promote growth and for normal body functions. See table 3.3 for the protein content of various foods (29).
Proteins should account for about 10 to 15 percent of total calories (AMDR is 10 to 35 percent for adults—see What Do All the Abbreviations Mean later in this chapter for a definition of AMDR) (10). As with carbohydrates, a range is provided to account for differences in diet and to suggest a safe upper limit. Depending on your total calorie intake, you may be near the low or high end of this range. Your personal protein requirement is based on your body weight; you should consume approximately 0.36 grams of protein for each pound of body weight. Simply multiply your body weight in pounds by 0.36 to determine approximately how many grams of protein you need to consume each day. If you know your body weight in kilograms, multiply that value by 0.8 (3). For example, for a 150-pound or a 68-kilogram person, this would be figured as shown:
150 pounds × 0.36 = 54 grams protein × 4 calories/gram = 216 calories from protein
68 kilograms × 0.8 = 54 grams protein × 4 calories/gram = 216 calories from protein
Note that protein requirements are increased for athletes and are different depending on the sport, the intensity and frequency of the workout, and how experienced the athlete is. Typical recommendations for strength-trained athletes (e.g., American football players, bodybuilders) and endurance athletes (e.g., marathon runners) are between 0.55 and 0.77 grams of protein per pound of body weight (or 1.2 to 1.7 grams of protein per kilogram of body weight) (3). Because many Americans already consume more than the Recommended Dietary Allowance for protein, athletes or other highly active people may already be consuming adequate protein. For those with inadequate intake, increased focus on consuming a variety of protein foods is recommended (30).
Do protein requirements change with age?
It is often believed that as individuals age, protein needs change. This is not necessarily true for the average healthy adult. The Dietary Reference Intakes recommend that adult males consume 56 grams of protein per day and adult females consume 46 grams of protein per day, regardless of their age (29). It is important to remember that these numbers are general guidelines for the average individual. Protein needs always vary depending upon the individual.
Determining Calorie Needs and Nutrient Ranges
Determining the number of required calories and target amounts from carbohydrates, fats, and proteins requires some simple calculations. As an example, consider a very active female (body weight is 135 pounds or 61.4 kg) who is in training for a marathon and includes resistance training a couple days per week as well. The first step is to determine how many calories are needed and then what targets she should have for various nutrients.
To provide an estimate of her calorie needs, check table 3.1 for the number of calories she needs per unit of her body weight. She is in the “very active” category given her running and resistance training activities. Thus, to determine calories needed, her body weight (135 pounds) is multiplied by 16.
135 × 16 = 2,160 calories
To keep things simple for calculating, round this off to 2,100 calories needed per day. Next the amount of calories she needs to consume from carbohydrates, fats, and proteins is determined. Starting with protein is easiest because this is based on her body weight. Because of her higher level of endurance training, an appropriate target is 0.55 grams per pound of body weight. Thus, body weight is multiplied by 0.55:
135 × 0.55 = 74.25 grams of protein
To check the percentage of calories from protein, multiply the grams by 4 (because there are 4 calories per gram of protein):
74.25 × 4 = 297 calories from protein
Thus, about 14 percent of her calories should be from protein (297 calories from protein divided by 2,100 total calories = 0.14, which is the decimal representation of 14 percent). For carbohydrate, an appropriate amount for someone with her high level of aerobic training is 60 percent of calories, so the remaining 26 percent should come from fat. The calculations are as follows:
2,100 × 0.60 = 1,260 calories from carbohydrate
2,100 × 0.26 = 546 calories from fat
These calculations provide some general targets to help create balance in her diet. Not every meal has to fall precisely within these percentages; rather, this is more appropriate to consider over the course of the entire day. Some meals may be higher in protein, whereas others may have more fat or carbohydrate. She needs to reflect on the foods and beverages consumed over the course of the day rather than becoming too focused on each food item or meal.
Now it’s your turn! Take this time to calculate your estimated calories from carbohydrate, protein, and fat. You can start with your daily caloric needs that you calculated earlier in this chapter. Remember that when calculating your calories you should choose the appropriate percentages for your lifestyle based on the ranges for each category. The ranges are 45 to 65 percent for carbohydrate, 10 to 15 percent for protein, and 20 to 35 percent for fat.
Fats, also called lipids, are provided in the diet from such sources as animal protein, butter, oils, nuts, and many refined products. Fats are often thought of as bad, a myth perpetuated by the many fat-free products flooding store shelves. However, fats are needed in appropriate amounts for normal functioning in the body (3). For example, lipids are the main component of each cell in your body. In addition, fat is a major source of energy, especially when you are at rest or performing low- to moderate-intensity physical activity. Excessive consumption of fat is unhealthy, but concerns also arise when fat intake is too low. A balanced approach to fat intake provides the necessary amount of fat for optimal health.
Fats are present in a number of forms, including saturated fats, monounsaturated fats, and polyunsaturated fats. These designations have to do with the chemical structure of the fat. Trans fats are found naturally in some animal products (mainly meat and dairy products), but also are a result of a manufacturing process called hydrogenation. Hydrogenation changes the structure of a fat to make it more stable and as a result more like saturated fats (which are solid at room temperature). Food companies hydrogenate fat to increase the shelf life of the product, to make it taste more like butter, and to save money because it is less expensive to hydrogenate oil than it is to use butter.
In general, health concerns result from consuming too much saturated and trans fats. Trans fats have been shown to increase the “bad” cholesterol in blood (low-density lipoprotein cholesterol, or LDL-C), even more so than saturated fats. Sources of trans fats include animal products, margarine, and snack foods. The good news is that as a result of health concerns, the food industry is reformulating many products to remove or at least reduce the amount of trans fat. Many restaurants have also now gone “trans fat free.” Companies that make processed food products are required to list the amount of trans fat in their products. Although some products have labels that state they are “trans fat free,” this actually means that they contain no more than 0.5 percent trans fat.
Monounsaturated fats, such as olive oil, canola oil, avocados, walnuts, and flaxseeds, have been shown to be protective against heart disease and type 2 diabetes mellitus. That is not to say that you can consume as much monounsaturated fat as you want; however, selecting monounsaturated fats instead of saturated fats may lead to better health (e.g., healthier blood cholesterol levels). Polyunsaturated fats, such as safflower oil, corn oil, and fish oils, have also been shown to be protective against many diseases. Fish oils (eicosapentaenoic [EPA] and docosahexaenoic [DHA]) have been shown to decrease inflammation within the body and may protect against heart disease, type 2 diabetes, and arthritis. This does not mean that EPA and DHA are protective against everything, but they are important to overall health. Therefore, you should try to consume 2 to 3 ounces (56 to 85 g) of fatty fish (e.g., tuna, salmon, and sardines) at least two days per week (30). Fish oil supplements may also be warranted (consult with your health care provider to see if this is appropriate for you).
Saturated fats are found in products such as butter, cheese, meat, palm oil, and whole milk. Because of the increased risk of disease associated with saturated fats, less than 10 percent of your calories should come from saturated fats (30, 32), with an even better target of less than 7 percent (32). Trans fats also should be limited to as little as possible (30). Because of the focus on saturated and trans fats, the nutrition labels on food products include total fat as well as the amount of saturated and trans fats (see figure 3.1).
Although not technically a fat, cholesterol is in the lipid family and is found in animal products. Your body needs a certain amount of cholesterol; thus, even if your diet contained none, the liver would produce what your body needs. The problem arises when cholesterol levels in the blood become too high. Total blood cholesterol levels, as well as LDL-C levels, are predictors of heart disease (for more information, see chapter 12). Although you consume cholesterol in your diet, a major factor influencing your blood cholesterol levels is the amount of saturated and trans fats you consume. Thus, limiting saturated fat intake to no more than 10 percent of your calories is recommended (no more than 7 percent is even better) (30, 32).
Total fat intake should be between 20 and 35 percent of calories (30). Most of these calories should come from monounsaturated and polyunsaturated fats (e.g., fish, nuts, vegetable oils), and your consumption of saturated fat should be limited. For example, for someone with a target of 2,500 calories per day, total fat intake should be between 20 and 35 percent of total calories. In this example, a target of 28 percent is selected (middle of the range). This would be approximately 700 calories from fat and would be calculated as follows:
2,500 × 0.28 = 700 calories
To keep saturated fat at no more than 10 percent of total calories, the calories from saturated fat would total only 250, determined as follows:
2,500 × 0.10 = 250 calories from saturated fat
To determine how many grams this represents, the calories from fat can be divided by 9 (recall that each gram of fat provides 9 calories). Thus, in this example, total fat would be around 78 grams (700 / 9 = 78), and saturated fat would be no more than around 28 grams (250 / 9 = 28).
Some of the food groups contributing to saturated fat intake are cheese, beef, milk products, frozen desserts, snack foods (e.g., cookies, cakes, doughnuts, potato chips), butter, salad dressings, and eggs. Making small changes in the foods you select could result in meaningful decreases in the saturated fat and calories you consume. See table 3.4 for some comparisons between higher- and lower-fat food selections (30).
What Do All the Abbreviations Mean?
Understanding what you need in your diet can be difficult. You can gain clarity by examining the Dietary Reference Intakes (DRIs) and Acceptable Macronutrient Distribution Range (AMDR), which are reference values and ranges for the amounts of nutrients your body needs. This looks like alphabet soup; however, each set of standards is helpful (9, 10).
DRI is an umbrella term. It includes the Estimated Average Requirement (EAR), the Recommended Dietary Allowance (RDA), the Adequate Intake (AI), and the Tolerable Upper Intake Level (UL). The DRIs are focused on the nutrition requirements of nearly all healthy people (i.e., they focus on 97 percent of that population). The DRIs are set by a committee established by the Food and Nutrition Board of the National Academy of Sciences.
· EAR—The nutrient values established when there is enough scientific information. Once an EAR is established, an RDA can be established for that particular nutrient.
· RDA—Target values established by scientists with a focus on preventing nutrition-related diseases.
· AI—Values set for nutrients when there is not enough scientific evidence to support establishing the RDA.
· UL—The upper limits established for nutrients to prevent toxic consumption levels (11). These were set because so many people take vitamin and mineral supplements.
The AMDR is not under the main umbrella of DRIs but rather provides ranges for the amount of carbohydrates, fats, and proteins (i.e., macronutrients) you should consume. The macronutrients are given in a range because the requirements vary among people more than those of the micronutrients (i.e., vitamins and minerals, which are covered by the DRI).
It is not necessary to obtain 100 percent of the established DRI for every nutrient every day; however, it is good to strive for at least 70 percent of the established DRI per day for each nutrient (9, 10). As you will see later in this chapter, the AMDR also provides guidance for dietary choices. All of the nutritional choices you make on a daily basis can make a difference for your health.
Micronutrients include vitamins and minerals. Minerals and vitamins, although part of energy-yielding reactions in your body, cannot provide energy directly. Many have antioxidant, or cell-protecting, functions (e.g., vitamins A, C, and E; copper; iron; selenium; and zinc). It is important to consume the DRI amounts for vitamins and minerals (or at least obtain 70 percent of the DRI) to maintain overall health (9, 10). It is beyond the scope of this chapter to discuss all the vitamins and minerals in detail; however, table 3.5 provides a listing of the major vitamins and minerals, including common sources as well as concerns with consuming too much or too little (11, 34).
Maximize Nutrient Density
Nutrient density reflects foods and beverages that provide vitamins and minerals with little or no added fats, sugars, refined starches, or sodium (30, 32). For example, dairy products are excellent sources of calcium, but many milk options are available. Consider 2 percent milk or nonfat (skim) milk. Which one would be preferred to optimize calcium intake while minimizing caloric intake? A 1-cup serving of each provides the same amount of calcium, vitamins, carbohydrate, and protein, but the 2 percent milk has a third more calories than the nonfat milk, all coming from added fat. See figure 3.2 for a comparison of the food labels for the two (31). Thus, the nonfat milk might be a better option since it provides the same amount of calcium at a lower number of calories.
Figure 3.2 Comparison of two milk products.
Source: U.S. Department of Health and Human Services.
You may be feeling overwhelmed thinking about consuming each of the macronutrients and the micronutrients (all the vitamins and minerals) each day. However, if you consume a diet that is varied, includes five to eight servings of fruits and vegetables per day, and is composed mostly of whole foods and less of processed foods, you will be doing your body good. You may also feel daunted by the idea of consuming five to eight servings of fruits and vegetables per day, but remember that these servings include fruits and vegetables (not five to eight servings of each!), and that a serving can be a medium banana, 4 ounces (118 mL) of 100 percent fruit juice, 1/2 cup of broccoli, and the like. The website ChooseMyPlate.gov can help you better understand serving sizes, as well as your particular requirements. See figure 3.3 for a peek at the premise behind the plate (28). When making food choices, consider the following simple guidelines:
· Whole grain is better than processed or white grain.
· More color is better than less color (e.g., dark green leafy vegetables, deep red vegetables and fruits, and dark blue or purple fruits have more vitamins and minerals than those with less color).
· Less-processed foods are best.
Figure 3.3 Illustration for MyPlate.
USDA Center for Nutrition Policy and Promotion.
Often, contemplating how to improve your diet is difficult because it is hard to know where to start. As with any change it is important to focus on short-term and long-term goals. Consider a long-term goal of cutting down on fat intake as well as improving the nutrient content of your diet (e.g., increasing consumption of whole grains, fruits, and vegetables). A short-term goal might be, I will pack my lunch (including vegetable sticks, lean meat sandwich on whole-wheat bread, piece of fruit, and a yogurt cup) rather than stopping at fast-food restaurants each day for the upcoming week. This is a SMARTS goal (see chapter 4 for more on SMARTS goals) (1). It is specific in terms of the activity as well as the time frame. At the end of the week, you can reflect on whether you packed a lunch (measurable). The goal provides for specific action to be taken (i.e., it is action-oriented) and is an activity that can be accomplished without excessive difficulty (i.e., it is realistic). A specific time frame is provided so that the action starts now rather than being too open-ended (i.e., it is timely). And finally, as you set goals, each will be self-determined. Following are other examples of short-term goals:
· To stop at a local farmer’s market each weekend for the next month to select enough fruit to provide at least two selections each day
· To include a salad with romaine lettuce, tomatoes, onions, peppers, and carrots, topped with low-fat vinaigrette dressing, for dinner on at least two days during the upcoming week
· To replace an afternoon candy bar from the vending machine with a piece of fruit and some almonds
Another, more in-depth way to monitor eating is to use an online tracking tool. Online tracking tools allow you to enter in the foods you eat in a given day and give you a breakdown of all your nutrients and the food groups you consumed within that day. Although there are many online tools to use, SuperTracker (www.supertracker.usda.gov), developed by the U.S. Department of Agriculture (USDA), has an extensive in-depth database (28). SuperTracker works by allowing you to track your meals by entering them into a personal profile. After meals are entered, the online tool is able to give an extensive breakdown of calories, carbohydrates, proteins, fats, and micronutrients. This can help you identify changes that you may need to make in your diet, whether it be increasing or reducing the intake of a certain food group or nutrient or increasing or changing your exercise routine (SuperTracker also allows for tracking of physical activity).
Although many tools are available for use, it is important that you focus on your own unique lifestyle and behaviors. Building on short-term goals and maintaining those healthy behaviors will ultimately result in success at reaching your long-term goal.
Water is a required nutrient for all living beings. Water is important for hydration; however, it may be valuable for disease prevention as well. For example, researchers have found a relationship between water intake and reduction of gallstones and kidney stones, as well as between water intake and colon cancer (6, 7, 16, 27). Similarly, maintaining a sufficient intake of water during flying may help reduce the risk of blood clots (12).
With respect to physical activity, water is important for hydration. When you are active, you need to remain in a euhydrated (balanced) state (26). The DRI for water is 2.7 liters (91 oz or 11 cups) per day for women and 3.7 liters (125 oz or 16 cups) per day for men (9). Water balance means that you are replacing the fluid you lose through sweating and urine production.
This may sound daunting, but remember, hydration does not occur just from drinking water. Water intake can be obtained from food, which makes up about 20 percent of total water intake, and as well as from other beverages. Thus, although water is an excellent source of fluid, other beverages, such as tea, milk, coffee, and 100 percent juice, can also fulfill your fluid needs (9).
Water is important for hydration during physical activity.
Sweating during exercise is one way the body tries to cool you (2). Sweat is composed of water as well as other substances such as electrolytes (sodium, potassium, and chloride) (17). The amount of electrolytes in sweat varies among people depending on sweat rate, fitness level, and electrolyte intake, as well as the temperature of the environment. Sodium (salt) is one electrolyte you may have noticed dried on your skin after prolonged sweating. Replacement of sodium lost in the sweat is not an issue for most people, considering that, in general, Americans consume far more salt than their bodies need (see chapter 12 for insight into how sodium intake can influence blood pressure).
You should start focusing on water balance before you are active by consuming fluids in advance of your exercise bout. While you are exercising, your goal should be to avoid excessive dehydration. For shorter workouts (less than an hour), consuming water is fine (26). For longer workouts, consider using a sport performance beverage that provides fluids as well as some carbohydrate and sodium (14). Ideally, by consuming adequate fluids, you can avoid dehydration. One simple way to check your hydration status is to look at the color of your urine; it should be a clear, pale yellow color (5). The darker the color of your urine the less hydrated you are. Another way to track fluid lost during exercise is to check your body weight before and after your workout. For each pound (0.45 kg) lost during exercise, you should consume about 16 to 20 ounces (475 to 600 mL) of water or sport performance beverage (26).
Nutrition and Weight
When you consume basically the same number of calories as you expend, your body weight remains relatively stable. If you want to gain or lose weight, you must manipulate this balance between calories consumed and calories expended.
Some people have a difficult time gaining weight. This can be a result of a higher than normal BMR or a high physical activity level. When weight gain is a goal, the focus is on gaining muscle and not fat weight. To do this in a healthy way, you should consume more frequent meals with healthy snacks. For example, in addition to three main meals, consume three snacks per day. Consuming about 300 to 500 calories more per day would result in about a 1-pound (0.45 kg) per week weight gain. Healthy snacks include yogurt, peanut butter and jelly sandwiches, cereal with milk, fruit smoothies, and turkey sandwiches. It is also important to continue to exercise to ensure that the weight gain is mostly muscle. In particular, resistance training is an important factor for building muscle (see chapter 6 of this book for more information on resistance training). Although it will take some time, the slower the weight gain, the more likely it will be to consist of muscle gain and not fat or water gain.
Weight loss is a more common goal than gaining weight. Losing weight involves a negative energy balance. This can be achieved by increasing exercise and decreasing caloric intake. See chapter 18, “Weight Management,” for more details on weight loss.
There are a number of supplements on the market today, resulting in a multibillion dollar industry. It is beyond the scope of this chapter to discuss all of the nutritional supplements that are sold. If you are thinking about taking a multivitamin–mineral supplement, you should analyze your diet first to assess if a supplement is required. The best way to obtain nutrients is through whole foods (e.g., fruits, vegetables, whole grains; foods that are not processed). An analogy that can serve is this: If a bucket is already full, there is no need to continue to fill it. If you are interested in taking a supplement, you should first check with your primary health care provider. If you do decide to take a multivitamin–mineral supplement, consider taking it every other day to enhance your ability to digest and absorb it and to save money.
When considering a supplement, be cautious, as dietary supplements are not regulated by the Food and Drug Administration (FDA). Reports have been made of supplements being contaminated or not containing what is stated on the label (i.e., either more or less). One way to check the safety of supplements is to look for third-party testers (e.g., NSF Certified for Sport, http://nsfsport.com/). These testers take common supplements and test them to see if their labels accurately represent what is actually in them, check that no adulteration has occurred, and report on their safety.
The best way to know if a supplement is harmful, helpful, or neutral is to meet with a Registered Dietitian, especially one who specializes in sports nutrition. In addition, some supplements interact or interfere with medications. A Registered Dietitian will be able to guide you on safe and correct choices. A reliable website that can also help you to know if a supplement is beneficial or harmful is from the National Institutes of Health (34):www.nlm.nih.gov/medlineplus (and see the Drugs and Supplements section).
Understanding the importance of macronutrients, micronutrients, water, and the Dietary Guidelines for Americans provides a framework for improving your diet. Knowing how to read labels and how to calculate your energy needs helps you make healthy choices regarding your diet. A healthy diet should include a wide variety of foods that you enjoy. Following the Dietary Guidelines for Americans is a good start to working toward consuming a healthy, varied, and nutrient-dense diet that will help prevent disease and give you more energy each day.