Lesson 23.1: Food and Nutrients
Lesson 23.1: Food and Nutrients
Lesson Objectives
Identify classes of macronutrients and describe their roles in the body.
Describe balanced eating and explain how it helps prevent obesity.
State functions and food sources of vitamins and minerals.
Describe eating disorders, their causes, and treatment.
Introduction
Did you ever hear the saying, “You are what you eat”? It’s not just a saying. It’s actually true. What you eat plays an important role in your health. Eating a variety of healthful foods promotes good physical health and provides energy for growth and activity. Many common diseases and their symptoms can be prevented or helped with healthful eating. Knowing what your body needs can help you choose foods to meet those needs.
Nutrients, Energy, and Building Materials
Nutrients are chemical elements or compounds that the body needs for normal functioning and good health. There are six main classes of nutrients: carbohydrates, proteins, lipids, water, vitamins, and minerals. The body needs these nutrients for three basic purposes: energy, building materials, and control of body processes.
A steady supply of energy is needed by cells for all body functions. Carbohydrates, proteins, and lipids provide this energy. Chemical bonds in molecules of these nutrients contain
energy. When the bonds are broken during digestion to form simpler molecules, the energy is released. Energy is measured in units called kilocalories (kcal), commonly referred to as Calories.
Molecules that make up the body are continuously broken down or used up, so they must be replaced. Some nutrients, particularly proteins, provide the building materials for this purpose. Other nutrients—including proteins, vitamins, and minerals—are needed to regu- late body processes. One way is by helping to form enzymes. Enzymes are compounds that control the rate of chemical reactions in the body.
Nutrients can be classified in two groups based on how much of them the body needs:
Macronutrients are nutrients that the body needs in relatively large amounts. They include carbohydrates, proteins, lipids, and water.
Micronutrients are nutrients the body needs in relatively small amounts. They include vitamins and minerals.
The exact amount of a macronutrient an individual needs depends on many factors, including gender and age. Recommended daily intakes of three macronutrients for young people of both genders are shown in Table 23.1.
Table 23.1: Recommended Daily Intakes of Carbohydrates, Proteins, and Water
GenderAnd Age Carbohydrates(grams/dParyo)teins(grams/day) Water*(liters/day)
Includes water in foods as well as beverages
Carbohydrates
Carbohydrates are organic (or carbon-containing) compounds consisting of the elements carbon, hydrogen, and oxygen. The elements are arranged in small molecules called sac- charides. Carbohydrates are classified as either simple or complex, based on the number of saccharides they contain.
Simple carbohydrates contain just one or two saccharides. They are all sugars. Examples of sugars in the diet include fructose, which is found in fruit, and lactose, which is found in milk. The main function of simple carbohydrates is to provide the body with energy. One gram of carbohydrate provides four kilocalories of energy. Glucose is the sugar that is used most easily by cells for energy. It circulates in the blood, providing energy to cells throughout the body. Glucose is the only source of energy used by the brain.
Complex carbohydrates, called polysaccharides, generally contain many saccharides. They include starches and fiber. Starches are found in plant foods such as vegetables and grains. They are broken down during digestion to form sugars that provide energy. Fiber consists of indigestible starches and other materials such as cellulose. It is present in all plant foods.
Fiber may be soluble or insoluble.
Soluble fiber dissolves in water as it passes through the large intestine. It helps form substances that keep blood levels of glucose stable and blood levels of harmful lipids low (see below).
Insoluble fiber does not dissolve but attracts water as it passes through the large intestine. This helps keep waste moist and moving easily through the intestine.
Proteins
Proteins are relatively large organic compounds containing carbon, hydrogen, oxygen, and nitrogen. The elements are arranged in small molecules called amino acids. Amino acids are the building blocks of proteins. They bond together to form long chains, called polypeptides. Proteins consist of one or more polypeptides.
Proteins play many vital roles in the body, including:
Making up the majority of muscle tissue.
Regulating many body processes.
Forming antibodies that destroy bacteria and other “foreign invaders.”
Regulating the salt-water and acid-base balance in body fluids.
Transporting nutrients and other vital substances in the blood.
Dietary proteins are broken down during digestion to provide the amino acids that cells need to make proteins for the body. Twenty different amino acids are needed for this purpose. Ten of these amino acids can be synthesized by cells from simple components. The other ten cannot be synthesized and must be obtained from foods. They are called essential amino acids because they are essential in the diet.
Proteins that contain all ten essential amino acids are referred to as complete proteins. They are found in animal foods such as milk and meat. Proteins that are missing one or more essential amino acids are referred to as incomplete proteins. They are found in plant foods such as legumes and rice. By eating a variety of different plant foods containing incomplete proteins, you can include all ten essential amino acids in your diet.
If you eat more protein than needed for the synthesis of new proteins by cells, the excess is used for energy or stored as fat. One gram of protein provides four kilocalories of energy. This is the same amount of energy that one gram of carbohydrate provides.
Lipids
Lipids, or fatty acids, are organic compounds that consist of repeating units of carbon, hydrogen, and oxygen. They provide the body with energy. The heart and skeletal muscles rely mainly on lipids for fuel. One gram of lipids provides nine kilocalories of energy, more than twice the amount provided by carbohydrates or proteins. Lipids have several other functions as well. Lipids form an insulating sheath around nerve cells that helps nerve messages travel more quickly. Lipids also help form substances that regulate blood pressure, blood clotting, and blood lipid levels. In addition, lipids make up the membranes that surround cells.
The term fat is often used interchangeably with the term lipid, but fats are actually a particular type of lipid, called triglycerides, in which three fatty acids are bound to a compound called glycerol. Fats are important in the body. They are the main form in which the body stores energy. Stored body fat is called adipose tissue. Stored fat not only provides an energy reserve but also cushions and protects internal organs. In addition, stored fat insulates the body and helps prevent heat loss in cold weather.
Although lipids and fats are necessary for life, they may be harmful if they are present in the blood at high levels. Both triglycerides and the lipid called cholesterol are known to damage blood vessels if their concentrations in the blood are too high. By damaging blood vessels, triglycerides and cholesterol also increase the risk of heart disease.
Lipids are classified as either saturated fatty acids or unsaturated fatty acids. This classifi- cation is based on the number of chemical bonds between carbon atoms in lipid molecules.
Saturated fatty acids have only single bonds between carbon atoms. This gives them properties that make them unhealthful. Their amount in the diet should be kept as low as possible. If consumed in excess, they contribute to high blood levels of cholesterol and triglycerides. Saturated fatty acids are found in animal foods, such as meat, whole milk, and eggs.
Unsaturated fatty acids have at least one double bond between carbon atoms. This
gives them properties that make them more healthful. Eaten in appropriate amounts, they may help lower blood levels of cholesterol and triglycerides and decrease the risk of cardiovascular disease. They are found mainly in plant foods.
The human body can synthesize all but two of the fatty acids it needs: omega-3 fatty acids and omega-6 fatty acids. Both are unsaturated fatty acids. They are called essential fatty acids because they must be present in the diet. They are found in salmon, vegetable oil, flaxseed, eggs, and whole grains. Small amounts of these two fatty acids may help lower blood pressure as well as blood levels of harmful lipids.
Unsaturated fatty acids known as trans fatty acids (or trans fats), are manufactured from plant oils and do not occur naturally. They are added to foods to extend their shelf life. Trans fats have properties like saturated fats and may increase risk of cardiovascular disease. They should be avoided in balanced eating. Many manufacturers no longer add trans fats to food products, and their use in restaurants has been banned in some cities.
Water
You may not think of water as a food, but it is a nutrient. Water is essential to life because it is the substance within which all the chemical reactions of life take place. An adult can survive only a few days without water. Table 1, above, shows water requirements for young people.
Water is lost from the body in exhaled air, sweat, and urine. Dehydration occurs when a person does not take in enough water to replace the water that is lost. Symptoms of dehydration include headaches, low blood pressure, and dizziness. If dehydration continues, it can quickly lead to unconsciousness and even death. When you are very active, particularly in the heat, you can lose a great deal of water in sweat. To avoid dehydration, you should drink extra fluids before, during, and after exercise.
Taking in too much water—especially without consuming extra salts—can lead to a condition called hyponatremia. In this condition, the brain swells with water, causing symptoms such as nausea, vomiting, headache, and coma. Hyponatremia can be fatal, so it requires emergency medical care.
Balanced Eating
Balanced eating is a way of eating that promotes good health. It includes eating several medium-sized meals regularly throughout the day. It also includes eating the right balance of different foods to provide the body with all the nutrients it needs. Table 1, above, lists macronutrient needs for young people, and you just read about foods that provide each of these macronutrients. How much of these foods should you eat to get the right balance of nutrients? Two tools for choosing foods that provide balanced nutrition are MyPyramid and nutrition labels on food packages.
MyPyramid
MyPyramid was developed by the U.S. Food and Drug Administration. It shows how much you should eat each day of foods in different food groups. MyPyramid is shown in Figure
23.1. You can visit the MyPyramid.gov website for more details or to customize MyPyramid for your gender, age, activity level, and other factors.
Guidelines for Using MyPyramid
The six colored bands represent six food groups:
Brown = Grains—At least half should be whole grains.
Green = Vegetables—Choose a variety of vegetables, including dark green and orange vegetables, dry beans and peas.
Red = Fruits—Include a variety of fruits, and consume whole fruits instead of fruit juices.
Yellow = Oils—Choose mainly unsaturated nut and vegetable oils.
Blue = Milk—Dairy products should be low-fat or fat-free choices.
Purple = Meat and Beans—Choose fish and low-fat meats, as well as beans, peas, nuts, and seeds.
The width of each colored band shows the proportion of food that should come from each food group.
The figure climbing stairs reminds you to balance food with exercise: 30–60 min/day of moderate-to-vigorous activity is recommended for most people.
Each food group represented by a colored band in MyPyramid is a good source of nutrients. The wider the band, the more you should eat from that food group. For example, the brown band is widest, so the largest proportion of foods should come from the grains group. The white tip of MyPyramid represents foods that should be eaten only in very small amounts or very infrequently. They include foods such as ice cream and potato chips that contain few nutrients and may contribute excess kilocalories to the diet.
The figure “walking” up the side of MyPyramid in Figure 23.1 represents the role of exercise in balanced eating. Daily exercise helps you burn any extra energy that you consume in foods. The more active you are, the more energy you use. Light activities, such as golfing, typically use only a few hundred kilocalories per hour. Strenuous activities, such as running, may use over 900 kilocalories per hour.
Harvard University recently developed an alternative healthy eating pyramid, which is shown in Figure 23.2. It differs from MyPyramid in placing more emphasis on exercise and a greater focus on eating fruits, vegetables, and healthy plant oils. It moves red meats and starchy, low-nutrient foods, such as white bread and white rice, to the category of foods to eat in very limited amounts. Some experts think that the Harvard pyramid is less confusing than MyPyramid and represents an even healthier way of eating.
Food Labels
Packaged foods are required by law to carry a nutrition facts label, like the one in Figure
23.3, showing the nutrient content and ingredients in the food.
Reading nutrition facts labels can help you choose foods that are high in nutrients such as protein and low in nutrients such as fat. Nutrition facts labels can also help you choose foods that are nutrient dense. Nutrient density is the ratio of nutrient content, measured in grams, to total energy content in kilocalories.
Table 23.2: Consider the following two foods:
Food A
Protein: 15 g
Energy: 300 kcal Nutrient Density:
15g/300 kcal = 0.05 g/kcal
Food B
Protein: 10 g
Energy: 120 kcal Nutrient Density:
10g/120 kcal = 0.08 g/kcal
Figure 23.2: Healthy eating pyramid. (3)
Figure 23.3: Nutrition facts label. (5)
In terms of protein, Food B is more nutrient dense than Food A, because it provides more protein per kilocalorie. Eating nutrient-dense foods helps you to get enough of each nutrient without taking in too many kilocalories.
Reading the ingredients list on food labels can also help you choose healthful foods for balanced eating. At the top of the list, look for ingredients such as whole grains, vegetables, and fruits. These are foods you need the most of in a balanced diet. Avoid foods that contain processed ingredients, such as white flour or white rice. Processing removes nutrients. As a result, processed foods generally supply fewer nutrients than whole foods, even when they have been enriched or fortified with added nutrients.
Weight Gain and Obesity
Any unneeded energy in food, whether it comes from carbohydrates, proteins, or lipids, is stored in the body as fat. An extra 3,500 kilocalories of energy results in the storage of one pound (0.45 kg) of fat. People who consistently consume more food energy then they need gain weight. People who continue to store fat and gain weight may eventually become obese.
Obesity occurs when the body mass index is 30.0 kg/m2 or greater. Body mass index (BMI) is a simple way to estimate the percentage of fat in the body. It is calculated by dividing an individual’s weight (in kilograms) by the square of the individual’s height (in meters). For example, a man who weighs 88 kilograms and is 1.7 meters tall has a BMI of:
88 kg ÷ (1.7 m)2 = 30.4 kg/m2.
Compare this BMI with the BMI values in Table 23.3. The man’s BMI is greater than 29.9 kg/m2, so he would be considered obese.
Table 23.3: Body Mass Index and Weight Status
BMI Value (kg/m2) Weight Status
<18.5 Underweight
18.5–24.9 Normal weight
–29.9 Overweight
>29.9 Obese
People who are obese are at greater risk of many serious health problems, including metabolic syndrome. Metabolic syndrome is a cluster of conditions that together greatly increase the risk of cardiovascular disease. The conditions include type 2 diabetes, high blood pressure, and high blood levels of LDL cholesterol and triglycerides. A wide range of other disorders may also be related to obesity, including menstrual disorders in females, certain types of cancer, osteoarthritis, and depression. In addition, people who are obese have a lower life expectancy.
From 1980 to 2002, the number of obese adults in the U.S. doubled. By 2004, almost one- third of U.S. adults aged 20 years or older were obese. The prevalence of obesity in the U.S. is the highest in the developed world. Given its prevalence and serious health risks, obesity is now a leading public health problem in this country.
The combination of eating too much and moving too little generally causes obesity. The best way to lose weight and avoid obesity is to eat less and exercise more. However, many factors may play a role in obesity, making it difficult for most people to eat wisely and lose weight. These factors may be genetic or environmental.
Several genes have been identified that control appetite and may contribute to some cases of obesity. An important environmental factor that contributes to obesity is the availability of high-fat, high-Calorie fast foods. Other environmental factors that may influence eating habits and contribute to obesity include stress, cultural traditions, and food advertisements. Some people who are obese have an eating disorder called binge eating. Eating disorders are discussed below.
Vitamins and Minerals
Unlike the major macronutrients, micronutrients—including vitamins and minerals—do not provide energy. Nonetheless, adequate amounts of micronutrients are essential for good health. The needed amounts generally can be met with balanced eating. However, many people do not eat enough of the right foods to meet their requirements. They may need vitamin or mineral supplements to increase their intake of micronutrients.
Vitamins
Vitamins are organic compounds that are needed by the body to function properly. There are 13 vitamins that humans need. They are described in Table 23.4, which also includes recommended daily vitamin intakes for teens.
Vitamins play many roles in good health, ranging from helping maintain vision to helping form red blood cells. Many vitamins are components of enzymes. For example, vitamin K is a component of enzymes involved in blood clotting. Several vitamins, including vitamins C and E, act as antioxidants. An antioxidant is a compound that neutralizes chemicals called free radicals. Free radicals are produced naturally during cellular activities and may cause some types of cancer. Neutralizing free radicals makes them harmless.
Some vitamins, including vitamin B6, are produced by bacteria that normally live in the intestines, where they help digest food. Vitamin D is synthesized in the skin when it is exposed to UV radiation in sunlight. Most other vitamins must be obtained from foods because the body is unable to synthesize them. Good food sources of vitamins are listed in the table below. They include whole grains, vegetables, fruits, milk, and nuts.
Consuming inadequate amounts of vitamins can cause deficiency diseases. For example, consuming inadequate amounts of vitamin D causes soft bones. In children this is called rickets. It can cause permanent bone deformities. Consuming too much of some vitamins can also be dangerous. Overdoses of vitamins can cause problems ranging from diarrhea to birth defects and even death.
Vitamins are either fat-soluble or water-soluble. This determines whether they can accumu- late in the body and lead to overdoses.
Vitamins A, D, E, and K are fat soluble. Excess intakes of these vitamins are stored in fatty tissues of the body. Because they are stored in the body, they can build up to toxic levels, especially if they are taken improperly in supplements.
Vitamin C and all the B vitamins are water soluble. Excess amounts of these vitamins are excreted in the urine, so they are unlikely to reach toxic levels in the body.
Table 23.4: Vitamins
Vitamin (Chemical Name)
Functions in the Body
Good Food Sources Recommended Daily
Intakes f or Ages 14–18 yr
Vitamin A (Retinoids)
Needed for good vi- sion, reproduction, and fetal develop- ment
Helps break down
Carrots, spinach,
milk, eggs Males: 900 g Females: 700 g
Whole wheat, peas,
Vitamin B1 (Thiamine)
Vitamin B2 (Riboflavin)
Vitamin B3 (Niacin)
macronutrients; es- sential for proper functioning of nerves
Helps the body pro- cess amino acids and fats; acts as antioxi- dant
Helps release energy from macronutri- ents; needed for healthy skin and nerves
beans, fish, peanuts, meats
Milk, liver, green leafy vegetables, al- monds, soybeans
Beets, beef liver, pork, turkey, fish, sunflower seeds, peanuts
Males: 1.2 mg
Females: 1.0 mg
Males: 1.3 mg
Females: 1.0 mg
Males: 16 mg
Females: 14 mg
Table 23.4: (continued)
Vitamin (Chemical Name)
Functions in the Body
Good Food Sources Recommended Daily
Intakes f or Ages 14–18 yr
Vitamin B5, (Pantothenic Acid)
Helps form critical enzymes for synthe- sis of macronutrients
Forms enzymes
Whole grains,
legumes, eggs, meat Males: 5 mg*
Females: 5mg*
Cereals, yeast, liver,
Vitamin B6 (Pyridoxine)
Vitamin B7 (Biotin)
Vitamin B9 (Folate)
needed for amino acid synthesis and energy storage
Enables synthesis of fatty acids; helps store energy; keeps level of blood sugar stable
Needed to make red blood cells
Needed for normal
fish, avocadoes, nuts, green beans
None
Liver, green leafy vegetables, dried beans and peas
Meat, liver, milk,
Males: 1.3 mg
Females: 1.2 mg
Males: 25 g*
Females: 25 g*
Males: 400 g
Females: 400 g
Vitamin B12 (Cyanocobalamin)
functioning of ner- vous system and for- mation of blood
Needed to make
shellfish, eggs Males: 2.4 g Females: 2.4 g
Citrus fruits such as
Vitamin C (Ascorbic Acid)
many biological chemicals; acts as antioxidant
Helps maintain
oranges, red pep- pers, broccoli, kiwi
Salmon, tuna, eggs,
Males: 75 mg
Females: 65 mg
Vitamin D (Ergocalciferol and
Cholecalcif- erol)
blood levels of cal- cium; needed for healthy bones and teeth
mushrooms Males: 5 g Females: 5 g
Table 23.4: (continued)
Vitamin (Chemical Name)
Functions in the Body
Good Food Sources Recommended Daily
Intakes f or Ages 14–18 yr
Vitamin E (Tocopherol)
Vitamin K (Naphthoquinone)
Acts as antioxidant; protects cell mem- branes from LDL cholesterol damage
Helps transport cal- cium; helps blood clot
Vegetable oils, nuts, green leafy vegeta- bles, whole grains, fish
Kale, spinach, Brus- sels sprouts, milk, eggs, soy products
Males: 15 mg
Females: 15 mg
Males: 75 g*
Females: 75 g*
Recommended daily intakes not established; figures given are adequate daily intakes.
Minerals
Dietary minerals are chemical elements that are essential for body processes. Minerals are inorganic, meaning they do not contain carbon. Minerals needed by humans in relatively large amounts (greater than 200 mg/day) are listed in Table 23.5. Minerals not listed in the table are called trace minerals because they are needed in very small amounts. Trace minerals include chromium, iodine, iron, molybdenum, selenium, and zinc.
Table 23.5: Minerals
Mineral Name (Sym- bol)
Functions in the Body
Good Food Sources Recommended Daily
Intakes (mg) for Ages 14–18 yr
Calcium (Ca)
Needed for nerve and muscle action; builds bone and teeth; helps blood clot
Helps maintain wa-
Milk, soy milk, green leafy vegetables, sar- dines
Table salt, most pro-
Males: 1300* Females: 1300*
Chloride (Cl)
ter and pH balance; helps form stomach acid
cessed foods Males: 2300* Females: 2300*
Table 23.5: (continued)
Mineral Name (Sym- bol)
Functions in the Body
Good Food Sources Recommended Daily
Intakes (mg) for Ages 14–18 yr
Magnesium (Mg)
Needed to form sev- eral enzymes
Component of
Whole grains, green leafy vegetables, nuts, seeds
Meat, poultry, whole
Males: 410
Females: 360
Phosphorus (P)
bones, teeth, lipids, and other important molecules in the body
Needed for muscle
grains Males: 1250
Females: 1250
Meats, grains, or-
Potassium (K)
and nerve function; helps maintain salt- water balance in body fluids
Needed for muscle
ange juice, potatoes, bananas
Table salt, most pro-
Males: 4700* Females: 4700*
Sodium (Na)
Sulfur (S)
and nerve function; helps maintain salt- water balance in body fluids Necessary com- ponent of many proteins
cessed foods Males: 1500* Females: 1500*
Whole grains,
meats, seafood, eggs Males: 1300*
Females: 1300*
Recommended daily intakes not established; figures given are adequate daily intakes.
Minerals play many important roles in the body. Most are found in the blood and cytoplasm of cells, where they control basic functions. For example, calcium and potassium regulate nerve and muscle activity. Several minerals, including zinc, are components of enzymes. Other minerals, including calcium, form the bulk of teeth and bones.
Minerals cannot be synthesized by the body. Good food sources of minerals are listed in Table 23.5. They include dairy products, green leafy vegetables, and legumes. Mineral deficiencies are uncommon, but inadequate intakes of a few minerals may lead to health problems. For example, an inadequate intake of calcium may contribute to osteoporosis, a disease in which bones become brittle and break easily.
Some minerals may be toxic in excess, but overdoses of most minerals are uncommon. Over- doses are more likely when mineral supplements are taken. Salt (sodium chloride) is added to many foods, so the intake of sodium may be too high in many people. Too much sodium in the diet can cause high blood pressure in some individuals.
Other Micronutrients
Recently, new micronutrients called phytochemicals have been found in plants. They occur primarily in colorful fruits and vegetables, like those shown in Figure 23.4. Thousands of phytochemicals have been discovered, and some have already been shown to lower the risk of certain diseases. For example, the phytochemical lutein helps reduce the risk of macular degeneration, an eye disease that leads to blindness. Lutein is found in many yellow and orange fruits and vegetables. Several phytochemicals, including some found in berries, have proven to be powerful antioxidants.
Figure 23.4: Good sources of phytochemicals. (9)
Eating Disorders
Eating disorders are psychiatric illnesses that involve abnormal patterns of eating. A person with an eating disorder has a compulsion to eat in a way that causes physical, mental, and emotional health problems. Typically, the person has an obsession with food and weight. Eating disorders are more common in females. One reason may be society’s focus on female appearance. The most common eating disorders are binge eating disorder, anorexia nervosa, and bulimia nervosa.
Binge Eating Disorder
Binge eating disorder is characterized by compulsive overeating. People with the disorder typically eat very large quantities of food in a short period of time. They may use food as a way to deal with painful emotions or stress. Many people with the disorder are overweight or obese. The disorder is rapidly increasing in prevalence and is now the most common eating disorder in the U.S. The rise in binge eating disorder is one reason for the dramatic increase in obesity in this country
Anorexia Nervosa
Anorexia nervosa is characterized by greatly restricted food intake and low body weight (BMI less than 17.5 kg/m2). People with anorexia nervosa usually have a distorted body image. They think they are too fat when they are actually too thin. They have an obsessive fear of gaining weight and voluntarily starve themselves. They may also exercise excessively to help keep their weight low. Females with anorexia nervosa usually stop having menstrual periods. The disorder mainly affects teenage girls and is extremely serious. At least 10 percent of people with anorexia nervosa die from factors related to the disorder.
Bulimia Nervosa
Bulimia nervosa is characterized by cycles of binge eating followed by purging to eliminate the food from the body. Purging may be achieved through intentional vomiting or excessive use of laxatives. People with this disorder typically have normal weight or weight slightly greater than normal. Repeated purging can lead to dehydration. Excessive vomiting can damage the teeth and organs of the digestive system. Bulimia nervosa occurs most often in teenage girls and young women.
Causes and Treatment
People with eating disorders usually have other mental health problems as well, most com- monly depression. Both depression and eating disorders may have the same underlying physiological cause: low levels of the brain chemical serotonin. The process of eating causes serotonin to be released and may lead to a temporary “high.” The process of purging may also have this effect in people with bulimia nervosa.
Environmental factors play a role in most cases of eating disorders, as they do with depression and other mental health problems. Childhood abuse may be one of these environmental factors. Many people with eating disorders report having been abused as children.
Eating disorders can be treated with psychiatric therapy or psychological counseling. Medi- cations may also be prescribed. Treatment usually includes resolving underlying emotional problems, as well as treating depression or other mental health disorders that are also present. In patients with anorexia nervosa, weight gain is also an important goal of treatment.
Lesson Summary
Macronutrients include carbohydrates, proteins, and lipids. They are needed in rela- tively large amounts to supply the body with energy and building materials.
Balanced eating can provide the body with the nutrients it needs without causing weight gain. Balanced eating includes eating a wide variety of healthful foods.
Vitamins and minerals are micronutrients. They are needed in relatively small amounts to control many body processes.
Eating disorders are serious but treatable psychiatric illnesses. They involve abnormal eating patterns and an obsession with food and weight.
Review Questions
Further Reading / Supplemental Links
Which classes of nutrients provide the body with energy?
How is obesity diagnosed?
Identify the two main classes of micronutrients and give an example of each.
What is an eating disorder?
If Jera is a 15-year-old female, how many grams of carbohydrates and proteins should she eat each day?
How can MyPyramid help you have a balanced diet?
Why is it more dangerous to consume too much of a fat-soluble vitamin than a water- soluble vitamin?
Compare and contrast anorexia nervosa and bulimia nervosa.
Sizer, Frances and Whitney, Ellie, Nutrition: Concepts and Controversies (10th edi- tion). Brooks Cole, 2005.
Whitney, Eleanor Noss and Rolfes, Sharon Rady, Understanding Nutrition (11th edi- tion). Wadsworth Publishing, 2007.
Willett, Walter, M.D. and Skerrett, P.J., Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Free Press, 2005.
National Academy of Sciences, Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. NAS, Institute of Medicine, Food and Nutrition Board, 1997. Available on the Web at
National Academy of Sciences, Dietary Reference Intakes for Energy, Carbohydrate,
Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. NAS, Institute of
Medicine, Food and Nutrition Board, 2002. Available online at:
National Academy of Sciences, Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. NAS, Institute of Medicine, Food and Nutrition Board, 1998. Available online at:
National Academy of Sciences, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. NAS, Institute of Medicine, Food and Nutrition Board, 2001. Available online at:
National Academy of Sciences, Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. NAS, Institute of Medicine, Food and Nutrition Board, 2000. Available online at:
Duyff, Roberta Larson, American Dietetic Association Complete Food and Nutrition Guide (3rd revised edition). Wiley, 2006.
Haas, Elson M. and Levin, Buck, Staying Healthy with Nutrition, 21st Century Edition: The Complete Guide to Diet and Nutritional Medicine. Celestial Arts, 2006.
Kotz, Deborah, “Eating Disorders: Binge Eating More Common than Anorexia and Bulimia.” U.S. News & World Report, 2007. Available online at:
http://health.usnews.com/usnews/health/articles/070205/5health.binge.htm.
Leitzell, Katherine, “‘Good Carbs’ Yield Newfound Benefits.” U.S. News & World Report, 2007. Available online at:
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Meadows, Michelle, “Nutrition: Healthy Eating.” MedicineNet, Inc., 2006. Available online at:
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www.pamf.org/teen/health/nutrition/veggieteens.html
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Vocabulary
anorexia nervosa Eating disorder characterized by greatly restricted food intake and low body weight.
bulimia nervosa Eating disorder characterized by cycles of binge eating followed by purg- ing to eliminate the food from the body.
binge eating disorder Eating disorder characterized by compulsive overeating. People with the disorder typically eat very large quantities of food in a short period of time.
carbohydrates Organic (or carbon-containing) compounds consisting of the elements car- bon, hydrogen, and oxygen; provides the body with energy.
complete proteins Contain all ten essential amino acids; found in animal foods such as milk and meat.
eating disorder Psychiatric illnesses that involve abnormal patterns of eating.
essential amino acids Amino acids that cannot be synthesized and must be obtained from the diet.
hyponatremia A condition in which the brain swells with water, causing symptoms such as nausea, vomiting, headache, and coma.
incomplete proteins Proteins that are missing one or more essential amino acids; found in plant foods such as legumes and rice.
lipids (fatty acids) Organic compounds that consist of repeating units of carbon, hydro- gen, and oxygen; provide the body with energy.
macronutrients Nutrients that the body needs in relatively large amounts; include car- bohydrates, proteins, lipids, and water.
metabolic syndrome A cluster of conditions that together greatly increase the risk of cardiovascular disease; include type 2 diabetes, high blood pressure, and high blood levels of LDL cholesterol and triglycerides.
micronutrients Nutrients the body needs in relatively small amounts; include vitamins and minerals.
minerals Inorganic chemical elements that are essential for body processes.
MyPyramid A visual representation of how much you should eat each day of foods in different food groups.
nutrients Chemical elements or compounds that the body needs for normal functioning and good health.
obesity Occurs when the body mass index is 30.0 kg/m2 or greater.
proteins Relatively large organic compounds containing carbon, hydrogen, oxygen, and nitrogen; made of amino acids.
saturated fatty acids Fatty acids with only single bonds between carbon atoms.
triglyceride Fat; a particular type of lipid in which three fatty acids are bound to a compound called glycerol.
unsaturated fatty acids Fatty acids with at least one double bond between carbon atoms.
vitamins Organic compounds that are needed by the body to function properly. There are 13 vitamins that humans need.
Points to Consider
You need nutrients for energy and building materials. Balanced eating provides you with foods that contain the nutrients you need. How does your body obtain the nutrients from food?
What processes break down food and make nutrients available to the body? What organs carry out the processes?
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