Marcia Schwartz, CMA (AAMA), is employed by an internal medicine practice in her hometown. She recognizes that many of the patients seen in the practice have diseases that are influenced by diet and lifestyle factors. She learned about the importance of good nutrition and wellness in her medical assisting program. In addition, Marcia has continued to attend workshops and read about current trends in nutrition, so she is prepared to provide assistance to her patients as directed by the physician.

While studying this chapter, think about the following questions:

• How can Marcia help her patients understand the importance of and suggested requirements for the primary nutrients?

• What should Marcia know about dietary guidelines for fat consumption?

• What is the importance of vitamins and nutrients and in what foods can they be found?

• How can Marcia educate patients using the new MyPlate Web site?

• Is Marcia able to teach patients the significance of the body mass index (BMI) and how it can be calculated?

• What are the general guidelines for therapeutic nutrition?

• Is it important that Marcia be able to teach patients how to read food labels?

• What factors contribute to a healthy lifestyle?

Good health is a state of emotional and physical well-being that is determined to a large extent by diet and lifestyle factors. Health promotion and disease prevention practices focus on sound nutrition, regular exercise, avoidance of smoking and tobacco, limited alcohol intake, management of stress, and avoidance of environmental contaminants. We are what we eat, because the food we consume is used to build and repair every part of our bodies. A well-nourished person is also better able to ward off infections. Consequently, a poor diet and risky lifestyle behaviors are directly related to multiple health problems.

The physician, the medical assistant, and the registered dietitian (RD) are all closely involved in the nutritive care of a patient. The physician prescribes the diet, and ideally the dietitian instructs the patient in how to follow it. If professional aid is not available, the medical assistant may be asked to discuss the diet with the patient, answer questions, and explain certain aspects of the modifications involved. The patient may hesitate to ask the physician details about a recommended diet, or he or she may call with questions about how to implement the diet after leaving the office. The medical assistant, therefore, frequently is the person to whom the patient turns for answers. You should be able to answer basic questions on healthy nutrition and should have a fundamental knowledge of the diets physicians most often prescribe.

Health Problems Related to Poor Nutrition and Lifestyle Factors

• Anemia: Low iron or folate intake

• Cancers: High-fat, low-fiber, low-complex-carbohydrate diet; high alcohol and sodium intake; sedentary lifestyle; tobacco use

• Constipation: Low fiber, inadequate fluids; high-fat diet; sedentary lifestyle

• Diabetes mellitus type 2: High-calorie, high-fat, low-complex-carbohydrate diet; obesity; sedentary lifestyle

• Hypercholesterolemia and atherosclerosis: High-fat, low-fiber diet; high sugar and alcohol intake; tobacco use; sedentary lifestyle

• Hypertension: High-calorie, high-fat diet; high alcohol and sodium intake; tobacco use; sedentary lifestyle; obesity; stress

• Osteoporosis: Low calcium intake; inadequate vitamin D intake or lack of sun exposure; high alcohol intake; sedentary lifestyle; tobacco use

• Stroke: High-fat, low-fiber, low-complex-carbohydrate diet; high alcohol intake; tobacco use; stress

People eat the way they do for many reasons. When encouraging patients to make significant changes in their diets, the medical assistant must be sensitive to these reasons. The choices people make about what they eat are greatly influenced by their background and relationships. Every culture, religion, and ethnic group has its own beliefs and practices with regard to food. For example, according to the Hindu religion, eating beef is forbidden. Certain Jewish practices govern the types of foods that are eaten and how they are prepared. Food is more than sustenance; it represents family and celebrations and has an entire psychological component that the medical assistant must recognize in order to care for the individual patient most effectively.

Reasons for People’s Food Choices

• Convenience: People choose what is easiest and quickest, including eating out and take-home meals.

• Cost: What a person can afford.

• Emotional comfort: “Feel good” foods are chosen based on cultural and psychological influences.

• Routine: People eat what they always eat out of habit, personal preference, and availability.

• Positive experiences: A food is associated with a fond memory, eaten by someone the person admires, or chosen because of the influence of marketing and advertising.

• Ethnic or regional influences: The person grew up with the food; it is associated with the individual’s cultural background; or it is part of the regional diet where the person lives.

• Health and weight: People think a particular food is good for them or will help them maintain or lose weight.

Cultural Eating Patterns

• Asian diets emphasize whole grains in the form of millet, rice, and noodles and also fruits, vegetables, legumes, and nuts and seeds; fats are derived largely from vegetable oils, such as peanut or sesame oils. Dairy products are not traditionally eaten. Protein sources typically are broiled or stir-fried fish and seafood, egg whites, tofu, and nuts.

• Latin American diets emphasize food from plant sources at each meal, especially maize (corn) and potatoes, in addition to fruits, vegetables, whole grains, beans, and nuts. Poultry, fish, and dairy typically are consumed daily and meat and eggs weekly.

• Mediterranean diets emphasize whole grains, fresh fruits and vegetables, and all types of legumes, such as beans, lentils, and peas daily; olive oil replaces other fats and oils; fish, poultry, and eggs are consumed weekly and meat monthly.

• Mexican diets emphasize corn or flour tortillas, cabbage, legumes, squash, tomatoes, corn, and potatoes daily. Dairy is used in the form of cheeses, but milk is not regularly consumed. Protein sources typically are fish, beef, poultry, lamb, and many types of beans.

Nutrition and Dietetics

The term nutrition refers to all the processes involved in the intake and use of nutrients. Nutrients are the organic and inorganic chemicals in food that supply the energy and raw materials for cellular activities. Nutrients include carbohydrate, fat, protein, vitamins, minerals, and water.

Metabolism is the process in which nutrients are used at the cellular level for growth and energy production and excretion of waste. Metabolism occurs in two phases, anabolism and catabolism. Anabolism is the building phase, in which smaller molecules, such as amino acids, are combined to form larger molecules, such as proteins. An example of anabolism is the creation by the liver of glycogen, a stored form of glucose. In this process, many units of glucose are combined to form a more complex glycogen molecule. Catabolism is the breaking-down phase, in which larger molecules are broken down and converted into smaller units, such as when stored glycogen is broken down into glucose molecules for energy.

Digestion is a combination of mechanical and chemical processes that occur in the mouth, stomach, and small intestine. These processes result in the breakdown of nutrients into absorbable forms, including amino acids, fatty acids, glycerol, and glucose. Most nutrients are absorbed in the small intestine and then carried by the bloodstream to all parts of the body.

The term nutrition also is used to indicate nutritional status, or the condition of the body resulting from the use of nutrients. Dietetics is the practical application of nutritional science to individuals. It is the combined science and art of feeding individuals or groups, given a wide range of economic factors and/or health conditions, according to the principles of nutrition and dietary management. A registered dietitian’s role is the promotion of good health through proper diet and the therapeutic use of diet in the treatment of disease.

Nutrients

To nurture life, the nutrients in food must perform one or more of three basic functions in the body: (1) provide a source of fuel or energy, (2) supply material to build and repair tissues, and (3) regulate metabolic processes. Because no one food supplies all the nutrients required, a combination of different foods is necessary to promote health. With a little planning, all the body’s needs can be met by a well-balanced diet. Dietary deficiencies result in undernourishment or malnourishment and may lead to a variety of diseases. Good nutrition is an important part of health promotion for all individuals but especially for pregnant women, young children, and the elderly.

The role of diet in supplying energy is crucial to body functions. Every action of the body, whether voluntary or involuntary, requires energy. Even when a person is asleep, the body still needs a source of energy to keep vital organs functioning. Basal metabolism is the amount of energy needed to maintain essential body functions. The basal metabolic rate (BMR) is the amount of energy used by a fasting, resting individual to maintain vital functions. The rate is determined by the amount of oxygen used and is defined in units of heat energy called calories (cal). Because this unit represents a relatively small amount of energy and because metabolism involves much larger amounts of energy, the large calorie (Cal), or kilocalorie (kcal), is commonly used. A kilocalorie is defined as the amount of heat required to raise the temperature of 1 kg of water 1° C.

Of the seven food constituents (carbohydrates, proteins, fats, water, minerals, vitamins, and fiber), only carbohydrates, proteins, and fats are capable of furnishing the body with energy. The amount of energy, or kilocalories, a person needs varies according to the individual’s activity level, basal metabolic requirements, and whether disease is present. Most adults age 20 to 40 require 1,800 to 2,200 kcal/day. A patient generally is said to be overweight or underweight depending on how his or her current weight compares with nutritional assessment standards. Obesity is likely to result when more calories are consumed than are expended or because of certain endocrine imbalances.

Nutrients can be categorized as those that are a required part of the diet and those that can be anabolized in the body. An essential nutrient cannot be manufactured by the body and therefore must be included in the diet or a deficiency disease occurs. Certain amino acids are examples of essential nutrients. A nonessential nutrient can be created in the body and therefore does not need to be included in the diet; for example, both cholesterol, which is manufactured in the liver, and vitamin D, which is synthesized from exposure to the sun, are nonessential nutrients.

Nutrient Components

Carbohydrates

Carbohydrates (CHO) are chemical organic compounds composed of carbon, hydrogen, and oxygen that are primarily plant products. They are divided into three groups based on the complexity of their molecules: simple sugars (e.g., table sugar, molasses, syrup, honey, candy, baked goods, and milk); complex carbohydrates (starch) (e.g., whole-grain products, cereal, pasta, rice, potatoes, legumes, fruits, vegetables, and seeds); and dietary fiber, which is found in bran, oatmeal, whole-grain breads, beans, fruits, vegetables, seeds, and dried fruits. Each has a function in health and consists of many variations. With the exception of fiber, carbohydrates are easily digested and absorbed into the body. Simple sugars are quickly absorbed, whereas complex carbohydrates must be processed before they can be absorbed in the intestinal tract. Dietary fiber is indigestible and passes through the gastrointestinal tract unchanged.

How Many Terms Can Apply to Bread?

Dietary guidelines recommend that at least half of the grains consumed each day come from a whole-grain source.

Whole grains contain the entire grain kernel—the bran, germ, and endosperm. People who eat whole grains as part of a healthy diet have a reduced risk of some chronic diseases. However, labels can be confusing. How do you know which is a healthy choice? Understanding the following definitions associated with grain foods can help. Review the definitions and see what you think about the healthiest grain choices.

• Bran—The tough, fibrous covering of a grain that is the primary source of fiber in grain products.

• Enriched or fortified bread—Since 1942, and with legislation amended in 1996 to include folate, the U.S. government has required that thiamin, riboflavin, niacin, folate, and iron be added to refined grain products because the process of creating white flour destroys these nutrients.

• Refined or white flour or bread—Bread produced through a process that removes the coarse parts of the grain (the fiber and nutrients); the flour is bleached to create the white color.

• Stone-ground flour—A process used to grind the grain; may include white flour.

• Unbleached flour—Similar to white flour in nutritional value and nutrient content.

• Wheat flour or brown bread—Bread made from wheat (white bread also is made of wheat) or any other type of flour that contains molasses to color the bread brown.

• Whole-grain or whole-wheat flour—Flour for which the entire grain kernel is ground; unrefined flour.

The main function of carbohydrates is to supply fuel for energy and for all basic cellular activities. To meet energy needs, carbohydrate is metabolized at a rate of 4 cal/g. When digested, carbohydrate is converted into glucose, which is carried by the bloodstream to cells that need energy. A small amount of concentrated glucose is stored in the liver and muscles as glycogen. This stored glucose is available to supplement dietary supplies of carbohydrate. As with all nutrients, excess amounts of carbohydrate are converted into fat and stored in the body as adipose tissue. In addition to serving as the body’s primary energy source, carbohydrate also is needed to regulate protein and fat metabolism. As long as sufficient amounts of dietary carbohydrate are available to meet the body’s energy needs, protein and fat are not needed to supply energy. This protein-sparing effect allows protein to be used for its intended purpose—the repair and growth of tissues.

Carbohydrate is used for energy with limited production of waste materials, whereas protein and fat metabolism creates byproducts that are challenging for the body to process and excrete. For example, the metabolism of fat for energy results in the production of ketone bodies, which can cause an increase in the acidity of the blood and possibly kidney damage from the excretion of ketones. In addition, the central nervous system (CNS) requires a constant minute-to-minute supply of glucose to function properly. Neurons find it difficult to use fat or protein for energy.

Dietary fiber, commonly called roughage, is the portion of a plant that cannot be digested or absorbed. However, fiber’s inability to be digested makes it an important dietary asset. Fiber adds bulk to the intestinal tract that stimulates peristalsis and promotes regular bowel movements. In addition, soluble fiber, which is found in oat bran, peas, beans, certain fruits, and psyllium, lowers blood cholesterol levels, reducing the risk of heart disease. Soluble fiber combines with cholesterol in the intestine and is excreted through the bowel, which prevents the absorption of cholesterol into the bloodstream. Insoluble fiber, which is found in whole grains and beans, promotes regular bowel movements, which prevents constipation and hemorrhoids. It also prevents diverticulosis by stimulating and toning the muscles lining the large intestine, and it is thought to help prevent colon cancer. The recommended daily fiber intake is 20 to 35 g, and 5 to 10 g of this should be soluble fiber. Table 30-1 identifies food sources of both soluble and insoluble fiber. Eating fruit unpeeled and eating raw vegetables can greatly increase the fiber content of the diet.

TABLE 30-1

Food Sources of Fiber

FOOD	SERVING SIZE	TOTAL FIBER (g)	SOLUBLE FIBER (g)	INSOLUBLE FIBER (g)
Spaghetti, cooked	1 cup	2	0.5	1.5
Whole-wheat bread	1 slice	2.5	0.5	2
White rice, cooked	½ cup	0.5	0	0.5
Bran flake cereal	¾ cup	5.5	0.5	5
Corn flake cereal	1 cup	1	0	1
Oatmeal, cooked	¾ cup	3	1	2
Banana	1 medium	2	0.5	1.5
Apple, with skin	1 medium	3	0.5	2.5
Orange	1 medium	2	0.5	1.5
Pear, with skin	1 medium	4.5	0.5	4
Strawberries	½ cup	1	0	1
Broccoli	½ cup	2	0	2
Corn	½ cup	1.5	0	1.5
Potato, baked with skin	1 medium	4	1	3
Spinach	½ cup	2	0.5	1.5
Kidney beans	½ cup	4.5	1	3.5
Popcorn	1 cup	1	0	1

From the American Dietetic Association: Accessed January 12, 2010. Available at www.eatright.org/cps/rde/xchg/SID-5303FFEA-A120B9BE/ada/hs.xsl/nutrition_5440_ENU_HTML.htm.

Recommendations for Carbohydrate Consumption

• Carbohydrates should account for 55% to 57% of the total calories consumed each day (i.e., 271 to 288 g for a 2,000-calorie diet).

• Fiber-rich fruits, vegetables, and whole grains should be eaten as often as possible.

• People should consume 15 g of fiber for every 1,000 calories eaten.

• The intake of simple sugars, especially sugar-sweetened drinks, should be reduced, and snacking on foods high in sugars and starches should be limited.

• Fruits and vegetables: Based on the typical 2,000-calorie diet, 2 cups of fruit and 2½ cups of vegetables should be eaten daily; a variety of dark green, orange, and starchy vegetables and legumes should be consumed.

• Whole grains: At least three 1-ounce servings should be eaten each day. Whole grains should make up at least half of the daily grain consumption. One ounce is equal to one slice of bread, 1 cup of dry cereal, or ½ cup of cooked rice, pasta, or cereal.

• Dairy: Includes milk, yogurt, cheese, and fortified soymilk. These provide calcium, vitamin D, potassium, protein, and other nutrients. Choose low-fat or fat-free products to limit calories and saturated fat. By age, the requirements are: children 9 years or older, teens, and adults—3 cups/day; age 4 to 8 years—2½ cups/day; and age 2 to 3 years—2 cups. One cup is equal to 1 cup of yogurt, 1½ ounces of natural cheese, or 2 ounces of processed cheese.

30-1

Critical Thinking Application

A patient, George Hawthorne, recently was diagnosed with hypertension and hypercholesterolemia. He has a family history of colon cancer. The physician recommends a high-fiber diet. Describe how Marcia could reinforce the physician’s information by explaining the purpose of dietary fiber, the difference between soluble and insoluble fibers, and the types of foods Mr. Hawthorne should include in his diet.

Fats

Fats are the storage form of fuel used to back up carbohydrates as an available energy source. Fat is a much more concentrated form of fuel, producing 9 cal of energy per gram when metabolized. Dietary fats, or lipids, provide essential fatty acids and are needed for the absorption of the fat-soluble vitamins, A, D, E, and K. Fat gives food flavor and creates a feeling of satiety or satisfaction after eating. Adipose tissue, the stored form of fat in the body, supports and protects vital organs, insulates the body to help in the regulation of body temperature, and plays an important role in protecting nerve fibers and relaying nerve impulses. Lipids are also crucial to cell membrane development.

Saturated and Unsaturated Fatty Acids.

When digested, fats are broken down into fatty acids and glycerol. The main building blocks of fat are fatty acids, which can be either saturated or unsaturated. Unsaturated fatty acids can take on more hydrogen under the proper conditions and therefore are less heavy and less dense. If fatty acids have one unfilled hydrogen bond, the fat is called monounsaturated. Olives and olive oil, peanuts and peanut oil, canola oil, pecans, and avocados contain monounsaturated fats. Polyunsaturated fats, such as safflower, corn, cottonseed, and soy oils, have two or more unfilled hydrogen bonds. Unsaturated fats are found in plants and are usually liquid at room temperature. Monounsaturated fat should be used as frequently as possible to replace saturated fat in the diet. Research on olive oil indicates it may offer some protection against heart disease and breast cancer, and canola oil is another rich source of monounsaturated fatty acids.

The chemical structure of a saturated fatty acid contains all the hydrogen possible; these fats, therefore, are denser, heavier, and solid at room temperature. Saturated fats are found in whole milk dairy products, eggs, lard, meat, and hydrogenated fats, such as margarine. Some saturated fats, such as those in soft margarines, are partially hydrogenated. These fats usually are soft at room temperature. Most saturated fats come from animal sources. The main exceptions are coconut and palm oils, which are of plant origin but are exceptionally high in saturated fat. The primary dietary factor associated with high blood cholesterol levels is a high intake of foods high in saturated fat.

What is a Trans Fat?

Trans-fatty acids are byproducts created when polyunsaturated oils are solidified by the addition of hydrogen. Manufacturers use this process to preserve food products, because they are much more resistant to rancidity after hydrogenation. This lengthens the shelf life of the processed food, and the product tastes better. Trans fats are found naturally in meat and dairy products, but Americans consume most of their trans fats in processed foods, such as margarine, crackers, cookies, doughnuts, biscuits, chips, frozen meals, french fries, and other items containing or fried in partially hydrogenated oils. Trans fats raise the level of low-density lipoprotein (LDL), the so-called bad cholesterol, and lower the level of high-density lipoprotein (HDL), or “good” cholesterol, in the blood. Scientific evidence indicates that saturated fat, trans fat, and dietary cholesterol combine to raise the LDL level, resulting in an increased risk of coronary heart disease (CHD). According to the National Institutes of Health, more than 12.5 million Americans have CHD, and more than 500,000 die from its complications each year. Since 1993, nutritional food labels have been required to list the amounts of saturated fat and dietary cholesterol in products. Since January, 2006, manufacturers also have had to include trans fats on the label if the amount exceeds 0.5 g per serving. Label readers should be cautious, however, because eating more than the designated serving size can drastically increase the amount of trans fats consumed.

Benefits of Omega-3 Fatty Acids

The omega-3 fatty acids have a number of beneficial effects in the body:

• They are present in large amounts in the cerebral cortex.

• They help form the retina.

• They have antiinflammatory effects, including improving the immune response, protecting blood vessels (e.g., the coronary arteries), and inhibiting the formation of blood clots.

Omega-3 fatty acids are found in cold water fish, including mackerel, salmon, tuna, and trout; in certain oils, including canola, flaxseed, soybean, and wheat germ oil; and in walnuts, soybeans, and soybean kernels. The benefits of omega-3 fatty acids can be obtained by consuming two servings of cold water fish weekly.

Foods High in Saturated Fat.

Even a fat-free food can become high in saturated fat, depending on how it is prepared (e.g., a fat-free potato cooked as french fries). Therefore, we not only need to lower our intake of foods with saturated fat, we also need to be cautious about how foods are prepared. Foods should be grilled, roasted, broiled, baked, or cooked in the microwave rather than fried. Only lean meats should be used, and visible fat should be cut off before eating. Low-fat or fat-free products should be substituted when possible. Some foods high in saturated fat include the following:

Whole-milk dairy products

Meat (especially red meat)

Coconut and palm oils

A triglyceride molecule is created when three fatty acids attach to a molecule of glycerol. This structure is the main storage form of lipids. Triglyceride molecules are transported throughout the body via the bloodstream as lipoproteins. Dietary fats determine the saturation level of triglyceride chains. The total amount of triglycerides in the blood is used as a diagnostic tool for determining a patient’s risk for hypertension and heart disease. The acceptable triglyceride range in men is 40 to 160 mg/dL; for women, it is 35 to 135 mg/dL.

Cholesterol.

Cholesterol is a nonessential nutrient that plays a vital role in metabolic activities. It is synthesized only in animal tissue, so it is not found in plant foods. The primary food sources of cholesterol are egg yolks and organ meats, although all animal sources of food contain cholesterol. As a nonessential nutrient, cholesterol also is manufactured in the body, particularly in the liver.

The confusion between “good” and “bad” fat stems from the distinction between the fat in food and the fat in our bodies. The good fats in our diet are monounsaturated and polyunsaturated fats. The bad dietary fats are cholesterol, trans fats, and saturated fats. As mentioned, the fat in our bodies is divided into two lipoprotein categories. The good fats, or high-density lipoproteins, carry cholesterol from body tissues or the bloodstream to the liver for metabolism and excretion. The bad fats, or low-density lipoprotein and very-low-density lipoprotein (VLDL), carry cholesterol to the cells. LDL and VLDL form atherosclerotic plaques on arterial walls, and these plaques frequently result in heart disease, hypertension, and strokes. However, serum LDL levels often can be successfully changed through diet. Using polyunsaturated and monounsaturated fat products reduces total serum cholesterol levels. In addition, using monounsaturated fats (olive, peanut, and canola oils) reduces LDL levels. Aerobic exercise is an important tool for lowering total serum cholesterol levels, increasing HDL levels, and reducing triglycerides. The higher the serum level of HDL, the greater the protection against cardiovascular disease. The normal HDL range is 30 to 80 mg/dL. A level below 40 is considered a major risk for heart disease, whereas a value of 60 or greater is thought to protect against heart disease. Heart experts recommend an LDL level below 100 mg/dL and an HDL level of 60 mg/dL or greater (Table 30-2).

TABLE 30-2

Total and Low-Density Lipoprotein (LDL) Cholesterol Level Recommendations

	TOTAL CHOLESTEROL (mg/dL)			LDL CHOLESTEROL (mg/dL)
AGE (yr)	ACCEPTABLE	BORDERLINE	HIGH	ACCEPTABLE	BORDERLINE	HIGH
2 to 20	<170	170-199	>200	<110	110-129	>130
>20	<200	200-239	>240	<130	130-159	>160

Another potential health risk from a high-fat diet is obesity. Too much fat in the diet is deposited in the body as stored adipose tissue. Currently fats make up 35% to 40% of the total calories in the American diet. Nutritionists and epidemiologists believe that reducing dietary fat to 30%, with saturated fat and trans fat making up no more than 10% of calories, would reduce the risks of cancer, atherosclerosis, hypertension, and heart disease.

Recommendations for Fat Consumption

• Keep total fat intake to 20% to 35%, or approximately 17 g of fat per day for a 2,000-calorie diet.

• No more than 10% of daily calories should come from saturated and trans fats.

• Limit cholesterol to less than 300 mg/day.

• Use only lean cuts and smaller portions of meat; trim visible fat.

• Substitute poultry and fish for red meat; remove poultry skin before eating.

• Avoid adding fat in the cooking process.

• Limit intake of organ meats and egg yolks.

• With an elevated serum cholesterol, limit eggs to two or three per week or use egg substitutes or egg whites only.

• Use low-fat or fat-free milk and milk products.

• Use low-fat or fat-free products.

• Choose liquid monounsaturated oils, such as canola or olive oil.

30-2

Critical Thinking Application

Mr. Hawthorne is attempting to control his hypercholesterolemia with diet and exercise. What recommendations about fat intake can Marcia make that will help him lower his total cholesterol and LDL levels and raise his HDL level?

Antioxidants.

Cholesterol has been high on the list of dietary villains for years and is thought to be a serious contributor to the development of heart disease. Recent studies indicate that the problem may lie not with the cholesterol itself but with the way it reacts with oxygen, or the process of oxidation, in the bloodstream. The normal body process of using oxygen for energy, combined with environmental factors, such as pollution and tobacco smoke, creates free radicals, which can cause cellular damage. Our bodies have developed mechanisms to protect us against oxidizing free radicals through the use of antioxidant vitamins C, E, and beta-carotene, but their amounts are not always sufficient. When enough antioxidants are circulating in the blood, cholesterol is prevented from oxidizing. If the level of antioxidants is insufficient, the opposite is true, and damage to arteries begins. Therefore, in addition to lowering cholesterol, saturated fat, and trans fat intake, increasing dietary intake of antioxidants may prove beneficial in preventing cardiovascular disease. Research indicates that a diet rich in antioxidant vitamins also may be linked to protection against some cancers and macular degeneration. Naturally occurring antioxidants are found in many fruits and vegetables and certain seasonings.

Foods That Contain Antioxidants

Vitamin C

Vitamin E

Beta-Carotene

Mixed Antioxidants

Proteins

Proteins are very large, complex molecules. They are composed of units known as amino acids, which are the materials the body uses to build and repair tissues. Twenty amino acids are necessary for normal growth and maintenance of tissues. Of these, eight are essential amino acids that must be included in the diet because humans do not have the enzymes necessary for their formation.

Proteins are classified according to whether they contain all essential amino acids in good proportion. Complete proteins come from animal sources and have a mixture of all eight essential amino acids. Incomplete proteins do not supply the body with all the essential amino acids. These are the vegetable proteins, which must be used in specific combinations because each is missing or extremely low in one or more of the essential amino acids.

To prevent the wasting of protein for energy and to permit the creation of needed amino acid compounds, dietary protein must be adequate, the diet must supply essential amino acids, and enough carbohydrate and fat must be consumed to prevent the burning of protein for energy. Fortunately, most foods have a mixture of proteins that supplement one another. Because little, if any, storage of amino acids occurs in the body, it is important that a source of protein be included at each meal. Patients with extensive burns or those with wound healing problems often are prescribed high-protein diets to encourage tissue regeneration. Healthy adult women need approximately 45 g of protein a day, and men need approximately 55 to 60 g. The average North American diet contains twice that amount. Excess protein is metabolized and either converted to glucose, burned as fuel, or stored as fat in adipose tissue.

Functions of Protein

• Builds and repairs body tissue, including new tissue, blood, enzymes, and hormones

• Aids the body’s defense mechanisms against disease by creating antibodies

• Regulates fluid and electrolyte balance

• Provides energy when carbohydrate and fat stores are depleted

Food Sources of Protein

• Complete proteins: Meat, fish, poultry, eggs, and dairy products

• Incomplete proteins: Whole grains (e.g., barley, bulgur, cornmeal, oats, rice, whole-grain breads), cashews, sesame seeds, sunflower seeds, walnuts; soy products, dried legumes, peanuts; broccoli, dark green, leafy vegetables

Recommendations for Protein Consumption

• Consume no more than 18% of daily calories from protein or approximately 91 g of protein per day for a 2,000-calorie diet.

• 2010 Dietary Guidelines for Americans, from the U.S. Department of Agriculture (USDA), recommends eating 5½ to 6 ounces of cooked lean meat, poultry, or fish each day.

• One ounce of meat equals one egg, ¼ cup of dry beans, 1 tablespoon of peanut butter, ½ cup of cooked beans, or ½ cup of tofu.

If incomplete proteins are the only source of protein in the diet, a food that is protein deficient in one amino acid should be eaten with one that is high in the same amino acid to get the needed mix of essential amino acids. Vegetarianism has become increasingly popular, and many different forms exist. Some vegetarians consume no red meat but eat fish and poultry. Lacto-ovovegetarians eat primarily vegetable foods but include eggs and/or dairy products in their diets. Lactovegetarians consume milk and milk products in addition to vegetables but no other animal sources of food. Vegans consume no animal proteins at all, relying solely on vegetable foods for protein.

Those who eat some animal protein in the form of fish, eggs, and milk generally are not at risk nutritionally. However, vegans must include a variety of vegetable foods to ensure the nutritional adequacy of their diets. To supply sufficient protein, vegetables that complement each other must be eaten together to get the correct proportion of amino acids. This is customarily done in the diets of different cultures. For example, in Mexico, beans are combined with rice, and in Middle Eastern countries, wheat bread is combined with cheese.

Tips for vegetarians from the USDA Web site (www.mypyramid.gov) include the following:

• Build meals around protein sources that are naturally low in fat, such as beans, lentils, and rice, rather than high-fat cheeses.

• Try calcium-fortified, soy-based beverages in place of milk.

• Try vegetarian products such as soy-based sausage patties or links and veggie burgers made from soybeans, vegetables, and/or rice.

• Add meat substitutes, such as tempeh (cultured soybeans with a chewy texture), tofu, or wheat gluten (seitan), to soups and stews to boost protein without adding saturated fat or cholesterol.

Examples of Nutritionally Balanced Incomplete Protein Combinations

Combining two or more sources of incomplete amino acids provides a complete protein. For example:

• Black beans and rice

• Peanut butter sandwich on whole-grain bread

• Split-pea soup with whole-grain bread

• Lentil soup and cornbread

• Walnuts, peanuts, and rice

• Whole-wheat pasta, broccoli, and spinach

• Sunflower seeds and navy bean soup

Vitamins (Micronutrients)

Vitamins are organic substances that occur in minute quantities in plant and animal tissues; they are needed for specific metabolic processes to proceed normally. Vitamins function as catalysts and help or allow metabolic reactions to proceed. Originally they were lettered or numbered as they were discovered. However, as they have been identified chemically, they have been given more specific names. In many cases their chemical names are as well known as their letter designations.

Vitamins are divided into two groups: fat soluble (A, D, E, and K) and water soluble (B complex and C). Some vitamins are nonessential, meaning they can be manufactured in the body. Vitamin A is produced from beta-carotene food sources such as carrots, pumpkin, and sweet potatoes. Ultraviolet light from the sun initiates the production of vitamin D in the skin. Vitamin K is created from intestinal bacteria.

Functions of Vitamins