Medical Assistant Exam: Clinical Procedures - Nutrition

Nutrition is the study of how nutrients are taken into and used by the body. A nutrient is a chemical substance obtained from food and used in the body to provide energy, build structural materials, support growth and maintenance, or repair body tissues. Good nutrition is one of the most important factors in health maintenance.

Digestion
The digestive system plays a major role in proper nutrition. There are four processes that occur in the digestive system: ingestion, digestion, absorption, and elimination.
- Ingestion is simply taking food into the body. This occurs at the mouth.
- Digestion is the breaking down of food into smaller components that the body can absorb. This occurs both physically and chemically, and starts at the mouth with chewing and continues through the gastrointestinal tract to the small intestine.
- Absorption is the method the body uses to transfer nutrients from the gastrointestinal, or digestive, tract into the bloodstream.
- Elimination is the method through which the body removes, or excretes, waste.

Energy Nutrients
Energy is defined as the capacity to do work. The human body needs energy to do physical and chemical work, which is critical in metabolism, the set of physical and chemical processes that maintain life in an organism. The body uses energy, which is measured in calories, in foods for a variety of functions:
- to create body heat
- to move muscles
- to conduct nervous signals
- to produce hormones
- to regulate functions such as heart rate
- to repair damaged tissues
Three energy nutrients—carbohydrates, fats, and proteins—have one thing in common: All can be converted into energy.

Carbohydrates
Carbohydrates are the main source of energy. They are categorized as simple and complex, depending on the amount of energy needed to digest them.

Simple Carbohydrates
Simple carbohydrates, commonly referred to as simple sugars, are abundant in many foods we eat. Two categories of simple carbohydrates exist: monosaccharides and disaccharides.

Monosaccharides are single units of sugar. The most common monosaccharides in the human diet are glucose, fructose, and galactose.
- Glucose is the sugar that the body uses most efficiently; most ingested sugar is broken down in the intestines and converted to glucose in the liver.
- Fructose is found largely in fruits.
- Galactose is a product of the digestion of lactose (see next paragraph).

Three disaccharides constitute the main dietary sources of sugar for humans: sucrose, lactose, and maltose.
- Sucrose is one of the sweetest sugars. It occurs naturally in many fruits and vegetables as well as in sugar cane and the sugar beet. Table sugar, or refined sugar, is a form of sucrose.
- Maltose is a result of the breakdown of starch, a complex carbohydrate (see next section).
- Lactose is a disaccharide commonly found in milk products.

Complex Carbohydrates
Complex carbohydrates, also known as polysaccharides, are made up of many units of monosaccharides, the simple sugars. There are three types of complex carbohydrates:
- Starch is the most important dietary complex carbohydrate. Starch is found in plants. There are two kinds of starch molecules: amylase and amylopectin. Examples of foods that are sources of starch are wheat, rice, potatoes, and legumes.
- Glycogen is only ingested in small quantities, but is an important form of glucose as it is stored in the body. It releases glucose into the bloodstream to raise blood glucose levels.
- Fiber is a special polysaccharide because it cannot be digested. Fiber provides bulk to feces and promotes intestinal motility.

The American Cancer Society recommends a high-fiber diet to help prevent cancer. These recommendations include:
- eating high-fiber foods such as fruits, vegetables, and whole-grain cereals
- daily intake of five or more servings of vegetables and fruits
- consuming less processed and red meats
- maintaining a physically active lifestyle
- maintaining a healthy weight
- limiting the consumption of alcoholic beverages

Proteins
Proteins are a class of essential nutrients made up of amino acids linked together in chains and branching patterns by peptide bonds. Proteins and their component parts—amino acids—serve several important roles in the functioning of the body:
- as enzymes
- as hormones
- as the basic structural units in body tissues and cells
While proteins can be described as an energy nutrient, producing energy is not their main function. Ingesting foods that are high in protein is important for the healthy functioning of the body. Since the body cannot synthesize all amino acids on its own, it must get what are called essential amino acids from the food that is ingested.

Fats
Fats (which are also called lipids) perform important functions as part of a balanced diet.
Fatty acids are the building blocks of many fats and can be saturated or unsaturated.
- Saturated: when every carbon molecule in the fatty acid is saturated with, or holds, as many units of hydrogen as possible. Saturated fats can be found in meat, butter, and egg yolk and can increase blood cholesterol levels.
- Unsaturated: when the fatty acid’s carbon molecules do not hold all the hydrogen atoms possible. The more unsaturated the fatty acid is, the more liquid the fat. Unsaturated fats are found in vegetable and olive oils and can decrease blood cholesterol levels.
There are three types of fats: triglycerides, phospholipids, and sterols, such as cholesterol.

Triglycerides and Phospholipids
Calories taken in through ingestion that are not immediately used are stored in the form of triglycerides. Most fat in the body—and in food—is stored in the form of triglycerides, which contain three fatty acids and a glycerol molecule. The more saturated the molecule, the larger it is and the more likely it will contribute to stagnation in the bloodstream and the formation of fatty streaks.
Phospholipids are similar to triglycerides. However, they contain two fatty acids and a phosphate group.
- The phosphate group on the phospholipids makes the molecule soluble in water.
- The fatty acid component makes it soluble in fat.
This property of dual solubility—unique in the body—allows phospholipid molecules to form cell membranes.

Sterols
Sterols are lipids that contain a sterol group, which is made up of four carbon structures. The most common type of sterol is cholesterol, which is derived only from animal sources, such as eggs, meat, fish, and poultry. Cholesterol becomes harmful when it forms deposits of fatty streaks and fibrous plaque along artery walls.
There are two types of cholesterol:
- High-density lipoproteins (HDLs) help carry cholesterol to the liver for breakdown and secretion.
- Low-density lipoproteins (LDLs) circulate in the bloodstream and transport cholesterol and triglycerides from the liver to the peripheral tissues.
For more information on lipids, see the Lipid Profile section.

Vitamins
Vitamins are organic compounds vital to human nutrition. Needed in small amounts, they support a range of metabolic functions that are critical to the proper functioning of the human body.
There are two general classifications: fat-soluble and water-soluble.

Fat-Soluble Vitamins
Fat-soluble vitamins are absorbed into the body through lipids, or fat, in the intestines. They are more easily stored in the body than water-soluble vitamins and have the potential for a unsafe higher buildup.
- Vitamin A: promotes vision and supports growth; obtained primarily from fortified milk and dairy products, such as cheese, and some vegetables, such as carrots
- Vitamin D: supports bone development; obtained primarily from sunlight and fortified milk and dairy products such as cheese, some seafood such as salmon and sardines, and some meat such as veal and beef
- Vitamin E: antioxidant that protects cellular structure; obtained primarily from nuts, seeds, vegetable oils, and leafy green vegetables
- Vitamin K: essential for blood clotting; obtained primarily from leafy green vegetables, such as spinach and kale

Water-Soluble Vitamins
Water-soluble vitamins, as the name indicates, can be readily dissolved in water, and are generally easily excreted in urine. Because of this, specified daily intake levels must be maintained.
- Vitamin B1 (thiamine): necessary for energy metabolism; obtained primarily from sunlight and milk
- Vitamin B2 (riboflavin): necessary for energy metabolism; obtained primarily from milk and dairy products, eggs, spinach, and broccoli
- Vitamin B3 (niacin): necessary for energy metabolism; obtained primarily in foods high in proteins, such as meats, poultry, and some seafood, such as shrimp, halibut, and tuna; peanuts are also a good source
- Vitamin B6: necessary for a range of health-related functions, including protein metabolism; obtained primarily from beans, meat, poultry, some seafood, and some fruits, such as bananas
- Vitamin B12: necessary for red blood cell production and supports nerve function and DNA synthesis; obtained primarily from fish, meat, poultry, milk, and other dairy products
- Vitamin C: plays an important role in the immune system; necessary for synthesis of collagen, a vital part of connective tissue; supports protein metabolism and has antioxidant properties; obtained primarily from citrus fruits, tomatoes, and red and green peppers
Some standard foods, such as cereals and milk, are routinely fortified to include essential vitamins and minerals.

Minerals
Minerals are inorganic elements that are generally needed in larger quantities relative to vitamins. They help in the formation of hard bones, as is the case with calcium, and also are an important part of metabolic function.
Two general classifications include the major minerals and trace minerals. Major minerals, such as calcium and sodium, are needed in larger quantities than the trace minerals, such as iron and copper.

Major Minerals
- Calcium (Ca): supports bone and teeth structure; necessary for muscle and blood vessel function; obtained primarily from milk and other dairy products; deficiencies can cause osteoporosis in adults, especially women, and rickets in children
- Chlorine (Cl): important part of stomach acid and critical to electrolyte balance; obtained primarily from table salt and meat; no known disorders result from deficiency
- Magnesium (Mg): helps support nerve and muscle function, important in maintaining heart rhythm; supports bone development and the immune system; obtained primarily from beans and peas (legumes), green vegetables such as spinach, nuts and seeds, and unrefined grains; deficiencies can cause muscle weakness and twitching, confusion and hallucinations, dysphagia, and lack of growth in children
- Phosphorus (P): important for energy metabolism, bone and teeth development, and obtained primarily from meats and fish; deficiencies can cause weakness, bone pain, and bone loss
- Potassium (K): supports nerve and muscle function and important to electrolyte balance; obtained primarily from citrus fruits, tomatoes, potatoes, soybeans, and some dried fruits, such as dates and raisins; deficiencies can cause muscle weakness, paralysis, confusion; disorders include hypokalemia, low levels of potassium, and hyperkalemia, high levels of potassium
- Sodium (Na): helps maintain fluid balance; obtained primarily from table salt and meat; disorders include hypertension, due to high levels of sodium
- Sulfur (S): important part of protein structure; obtained primarily from milk, other dairy products, meats, eggs, and other foods containing protein; no known disorders result from deficiency

Trace Minerals
- Copper (Cu): important in many enzymes, necessary for the absorption of iron; obtained primarily from whole grains, nuts, beans and peas, and seafood; deficiencies can cause bone loss and anemia
- Iodine (I): critical component of thyroid hormone, which regulates growth and development; obtained primarily from iodized table salt and saltwater seafood; deficiencies can cause goiter
- Iron (Fe): critical part of the hemoglobin protein that carries oxygen to tissues, important for cellular development; obtained primarily from red meat, poultry, seafood, beans, and dark green leafy vegetables, such as spinach; deficiencies can cause anemia and fatigue
- Zinc (Zn): supports the immune system, important in protein and DNA development, helps wound healing, and supports the senses of taste and scent; obtained primarily from oysters, red meats, and some whole grains, nuts, and beans; deficiencies can cause stunted growth in children, hair loss, night blindness, slow wound healing, and skin problems
Other trace elements include chromium, molybdenum, selenium, cobalt, and fluorine.

Water
Water is an essential non-energy yielding nutrient. Water is the most abundant molecule in the body and makes up 65% of body weight in males and 55% in females. Without adequate water intake, the body cannot survive. Water is critical in a range of functions.
- part of intracellular fluids that allow chemical reactions to occur within cells
- part of extracellular fluids that allow transport of nutrients to cells
- removal of toxic waste from the body
- major component of blood
- control of bodily temperature by eliminating excess heat through the evaporation in the form of perspiration
The recommended amount of water that should be consumed in one day is eight eight-ounce glasses.

Dietary Guidelines
A variety of dietary guidelines exist to help people obtain proper nutrition, reduce the occurrence of disease, and control weight. These recommendations suggest the types and quantities of food that people should eat each day. They may also contain recommendations about which types of foods to limit and which types of foods to increase, given the specific health status of an individual.

USDA Dietary Guidelines for Americans
The U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (HHS) have established dietary guidelines. These guidelines encourage people to eat a balanced diet, limit consumption of less nutritious foods, increase physical activity, and make good nutritional decisions consistently. Much of the information on these guidelines—and in this section—can be found in Dietary Guidelines for Americans, published jointly by the USDA and HHS, and can be found at http://www.health.gov/dietaryguidelines.

Key Recommendations
The USDA dietary guidelines recommend that individuals balance the food they eat with physical activity. The USDA guidelines also recommend that individuals maintain or reduce their weight to help reduce the possibility of high blood pressure, heart disease, stroke, some types of cancer, and diabetes.
Specific recommendations in the USDA guidelines include:
- Maintain an adequate nutrient intake while monitoring caloric needs.
- Consume a variety of nutritious foods from the basic food groups.
- Avoid foods that contain saturated fat, trans fat, sugar, and salt.
- Restrict alcoholic beverages.
- Maintain body weight in a healthy range.
- Exercise regularly and reduce sedentary activities.
- Balance calorie consumption with physical activity.
- Prevent gradual weight gain over time.

Food group recommendations by the USDA include:
- Eat a lot of fruits and vegetables, and a wide variety of them, each day while staying within energy requirements.
- Consume three or more servings of whole grains per day.
- Consume three cups of fat-free or low-fat milk or equivalent each day.
- Limit amounts of fats and oils that are high in saturated and/or trans fatty acids.

Carbohydrate recommendations from the USDA:
- Stick with fiber-rich fruits, vegetables, and whole grains.
- Stay away from foods that are high in simple sugars.
In addition, the USDA advises individuals who drink alcoholic beverages to do so in moderation. Alcoholic beverages should not be consumed by pregnant or lactating women, individuals who take medication that can interact with alcohol, and children and adolescents. Avoid alcoholic beverages if engaging in activities that require skill and coordination.

USDA Food Guide Pyramid
Continued research on obesity by the U.S. Department of Agriculture and the U.S. Department of Health and Human Services led to the 2005 redesign of the food pyramid, which was initially introduced in 1988, to include emphasis on eating more fruits, vegetables, whole grain foods, beans, and nuts, and to include less emphasis on carbohydrates.
The new food pyramid can be found at http://www.mypyramid.org. It is designed to help balance nutritional and physical activity needs, and the medical assistant can use the pyramid and its guidelines, scheduled to be updated in 2010, as a source of information on maintaining a healthy diet.
The new pyramid presents color-coded vertical wedges, with each color representing a food group and the size of the wedge suggesting the relative amount of food to be eaten from each group.
- The orange, green, and red wedges—representing grains, vegetables, and fruits respectively—are the largest.
- The blue wedge is also relatively large; this represents milk and other calcium-rich foods, which the guidelines caution should be limited to low-fat or fat-free.
- The purple wedge is somewhat smaller than the blue wedge and represents beans and meats.
- The yellow wedge is the smallest and it represents oils.

To help patients plan a balanced diet, the medical assistant will need to know how much of a food equals a serving. For example, one serving of fruit equals one medium apple or orange, 1/2 cup canned fruit, or 3/4 cup (6 ounces) of fruit juice.
The food guide pyramid is a general guideline, and lists ranges of serving amounts. It does not provide exact information about what to eat. Nutritional needs vary from person to person, depending on age, gender, and activity level.
Some patients may have special dietary preferences or choices. For example, vegetarians do not eat meat, poultry, and fish. In order to provide vegetarians with guidelines for healthful eating, the American Dietetic Association has developed a food guide pyramid specifically for these individuals.

Special Diets
Nutritional needs vary for people in different stages of life depending on their health status.

Pregnancy
During the second and third trimesters of pregnancy, calorie needs are increased. Pregnant teenagers and underweight women may require even more of an increase. Extra calories should be nutrient-dense foods with an emphasis on increasing levels of nutrients needed for fetal development and growth.
The medical assistant should advise pregnant women to limit processed foods, because nutrients are less available in those foods than in whole foods. Problems associated with pregnancy can include nausea and constipation. The pregnant woman can lessen nausea by eating small, frequent meals; eating dry toast or crackers; and avoiding foods with strong odors.

Children
From infancy through adolescence, children’s nutritional needs change. The medical assistant must have an understanding of a child’s nutritional status in relation to overall nutritional health in the developing child. A child’s nutritional needs can be summarized in three basic phases: infancy, age two to 12, and adolescence.
Infancy to age two: This age group is further broken down into three age groups.
- From birth to age six months, an infant should be fed breast milk or formula exclusively. Studies have shown that introducing solid foods before six months leads to an increased risk of food allergies.
- From age six months to one year, breast milk or formula should still make up most of an infant’s diet. However, at six months, the parent or caregiver can begin introducing solid foods, such as cereals, vegetables, and fruit.
- By age one, the child can transition from breast milk or formula to whole milk and eat an expanded diet that includes whole wheat crackers, cheese, applesauce, bananas, scrambled or hard boiled eggs, vegetables, fruits, and meats.
Ages two to twelve: Starting at age two, the child’s diet should include a variety of dairy products, meats, beans, vegetables, fruits, bread, pasta, and cereals. As the child ages and tastes vary, the diet can grow to include more seasonings and varied flavors. Portion sizes will increase as the child grows, requiring more calories.
Adolescence: Adolescents undergo periods of rapid growth, such as the onset of puberty, that require more energy. The appetite of teenagers varies, but their diet should always include healthy foods, not empty calories that offer limited nutritional value. The medical assistant can advise his or her young patients to drink milk to build strong bones and to avoid soda, which adds unnecessary sugar to the diet. The medical assistant can also advise adolescent female patients that additional iron in the diet is necessary to replace iron lost in menstrual blood; this additional dietary iron may help symptoms of fatigue during menses.

Older Adults
As a person ages, he or she may become less active. A decrease in activity slows metabolism and, thus, decreases the need for calories. If eating habits of early adulthood do not change, weight gain will ensue. A decrease in activity is commonly due to painful arthritis or other medical complications. The medical assistant should encourage patients to exercise within their ability in order to avoid weight gain and promote good health. Special nutritional concerns of the aging adult include:
- Dentition—Patients with ill-fitting dentures may have trouble chewing and swallowing. High-nutrition soft foods (such as yogurt or soft cheese) provide the needed calcium.
- Income—Patients on a fixed income are sometimes forced to reduce food expenditures. Because carbohydrates are inexpensive, these patients may not get the protein and fresh fruits and vegetables needed for good health. The medical assistant can investigate government assistance (such as food stamps) for patients in need.
- Sense of taste—As people age, their sense of taste decreases. Because the sweet taste is strongest for elderly patients, they may crave sweets. Thus the medical assistant should emphasize the importance of controlling the amount of sweets in the diet.
- Digestive disorders—Digestive enzymes and stomach acids decrease as a person ages. These changes may create symptoms of heartburn, gas, and acid reflux that can discourage eating. Treatment for digestive disorders will allow more balanced food choices.

Dietary Restrictions
Sodium-Restricted Diet
Patients with kidney disease, high blood pressure, edema, or cardiovascular disease may benefit from a sodium-restricted diet. Because many processed foods contain a lot of sodium, the diet consists of natural foods and no addition of table salt. Although there are low-sodium processed foods available, such as tomato sauces, soups, and pretzels, patients must read labels and understand the amount of sodium included in each serving of the food.
Patients must pay close attention to the salt content of any condiments they may use. High-sodium condiments include ketchup, pickles, mustard, mayonnaise, and salad dressing. Spices can be added to foods to enhance flavor as long as no sodium is added.

Weight-Loss Diets
Weight-loss diets are numerous and can vary in approach. Low-fat or low-carbohydrate diets can yield weight loss; however, patients may tolerate them differently.
A healthy weight-loss diet does not promise dramatic weight loss in a short period of time and must not compromise nutrient supply. Patients should focus on losing weight safely by focusing on balanced nutrition and exercise; this approach will more likely allow a patient to keep weight off in the future.

Lactose Sensitivity
Lactose, the sugar contained in human and animal milk, must be broken down in the body by the enzyme lactase to enable the body to digest dairy products. In people from some parts of the world, lactase is present in the body until age three or four, after which it all but disappears. As a result, after early childhood, many people have trouble digesting foods that contain lactose and eliminate these foods from their diets. People who are especially sensitive to dietary lactose are often referred to as being lactose intolerant.
Chemical preparations can help a person digest lactose. Those preparations may be added to certain foods, such as ice cream, for lactose-sensitive people. If people with a lactose sensitivity choose to avoid dairy products, they need to be sure to obtain protein and calcium from other sources.

Heart Disease
Coronary heart disease that is caused by atherosclerosis usually results from hyperlipidemia, or an excess of lipids in the bloodstream. Left untreated, this condition can lead to angina (chest pain), heart attack, or stroke.
Patients can significantly lower their risk by reducing their blood cholesterol levels and losing weight if they are overweight. Patients who have coronary heart disease usually must reduce their consumption of fats to a level that provides less than 30% of their total caloric intake. Saturated fats should provide less than 10% of caloric intake. Patients who have had a heart attack or are at increased risk for a heart attack are also encouraged to increase their consumption of soluble fiber.
The medical assistant should encourage patients to follow the nutritional regimen prescribed by the doctor. The medical assistant must not recommend other dietary changes. Instead, the medical assistant should educate patients about ways to reduce the amount of fat in their diets, such as by substituting skim milk for whole milk.

Soft Diets
Soft diets include foods that are easy to digest and are commonly prescribed for gastrointestinal problems to reduce strain on the GI tract. The diet consists of milk, yogurt, and soft cheese; cooked and pureed vegetables and fruits; pastas; and ground beef or chicken.

Diabetes
The physician will prescribe a diabetic diet to focus on frequent, small meals—a regimen that will decrease fluctuations in blood glucose levels. The diet also emphasizes foods with a lower glycemic index, meaning foods that take less time to raise blood glucose levels. Foods to avoid include candy, donuts, cakes, syrups, and alcohol.