Pharmacology and Nutrition

After studying this chapter, the student will be able to:

1.      Identify the roles of protein, fat, and carbohydrate in human nutrition

2.      List the major vitamins and minerals required for health

3.      List the fat-soluble and water-soluble vitamins and indicate the common circumstances in which a deficiency of each could occur

4.      Apply the nursing process for clients receiving total parenteral nutrition (TPN)

 

It has been well established that about 50 nutrients are required by the human

body. Of these, 10 are considered “leader nutrients”—protein, carbohydrate, fat,

vitamin A, vitamin C, thiamine, riboflavin, niacin, calcium, and iron. If proper

amounts of these nutrients are supplied in the diet, the other 40 will probably be

consumed in amounts sufficient for the body’s needs. The level of these “leader

nutrients” is usually listed on the information panels of food labels, thereby permitting the consumer and health professional to compare the nutritional content of various food products.

 

Estimates of daily requirements of most of the 50 required nutrients, known as

Recommended Daily Allowances (RDA), have been established and published periodically by the National Research Council (NRC). The RDA of a nutrient is the level of intake considered by the NRC Food and Nutrition Board to be adequate, on

the basis of available scientific knowledge, to meet the known nutritional needs of

practically all healthy persons. In using the RDA levels, one should remember that

they are:

Recommendations for the total amount of nutrient that should be consumed each day.

Allowances must be made for nutrient losses possible in food processing and preparation

Recommendations meant to maintain health and may not cover special nutritional needs that arise during illness estimates of the needs of most members of large population groups and may not be appropriate for each member of the group.

Nutrients may be classified into several categories, including proteins, fats, carbohydrates, vitamins, and minerals. Each of these categories is considered briefly.

PROTEIN

Protein is essential for the synthesis, maintenance, and repair of body tissues; for energy production; for the continuation of enzymatic and immunological processes; and the maintenance of osmotic pressure in the vasculature. Protein is made up of component parts known as amino acids. Of the 22 amino acids, 8 are considered essential, or indispensable, for human nutrition; the body cannot synthesize them at levels sufficient to meet its needs. During digestion, dietary protein is broken down into its amino acid components. The body then reassembles the amino acids into many different proteins, each serving a specialized function. Different foods supply protein of differing value to the human body, depending upon the nature of the amino acids in the protein source. Highquality protein (e.g., protein derived from meat, fish, poultry, eggs, and milk) supplies the 8 indispensable amino acids in usable proportions.

Protein derived from vegetables and grains is often lower in nutritional quality, because certain essential amino acids may be missing or in insufficient quantity. By carefully combining protein from varying sources, adequate amino acid intake can be assured.

Protein generally supplies about 4 large calories(kcal) of energy per gram. Clients who cannot digest dietary protein properly may use products containing the essential amino acids in their pure form. These may be supplied orally in the form of an elemental diet or parenterally as part of a total parenteral nutrition (TPN) regimen.

FAT

Fat is a very concentrated dietary source of energy that supplies about 9 kcal/g of energy. Fat provides the body with essential fatty acids and, along with carbohydrates, helps to spare protein for its tissue-building and repairing functions. Fat is also a carrier of fat-soluble vitamins (A, D, E, and K), hormones, and components of human cell membranes. Fat deposits in the body also help to support vital organs and provide insulation.

During digestion, dietary fats are broken down to fatty acids. One of these, linoleic acid, is essential for life and must be supplied by the diet, as the body cannot manufacture its own supply. A deficiency of fatty acids rarely occurs, because the body’s daily need for fat can be met with only 15–25 g of dietary fats. At greatest risk for development of essential fatty acid deficiency are clients receiving special nutritional therapy utilizing elemental oral feedings or TPN as the sole nutritional source.

CARBOHYDRATE

Sugars and starches are the principal kinds of carbohydrate. Starches are complex forms of sugar. Most sugars and starches are eventually converted by biochemical reactions of the body to glucose (one of the body’s most important fuels). It is either readily utilized by the cells and tissues of the body or it is stored by the liver and muscles as glycogen. The availability of carbohydrates as an energy source spares protein from being used for energy, thereby allowing it to be used for tissue

growth and repair. Carbohydrates also aid in fat utilization and prevent the breakdown of fat in the body. When utilized by the body, carbohydrates contain about 4 kcal/g of energy.

 

MINERALS

Minerals are found in water and in natural foods. They may be divided into two groups: major elements and micronutrients. The major elements are calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. The

micronutrients are iron, copper, iodine, manganese, zinc, fluorine, cobalt, chromium, molybdenum, and selenium

 

Micronutrients (Trace Elements)

Many chemical elements play an important role in the functioning of the human body even though their concentration may be quite low. Among these trace elements are copper, chromium, and selenium. Copper is associated with iron in

enzyme systems and hemoglobin synthesis. Chromium is associated with glucose metabolism and lowers serum cholesterol (LDL— low-density lipoproteins) and increases HDL—high-density lipoprotein commonly known as “good cholesterol.” No RDA standards have been established for copper or chromium. Selenium is a structural component of teeth and is a synergistic antioxidant with vitamin E. Recent studies have shown it to be useful in both preventing and treating

prostate cancer. The RDA of selenium is 55 mcg/d. Deficiencies of these substances are rare since they are often present in minute amounts in many dietary sources. Deficiencies of micronutrients may occur when a client is exclusively consuming

a carefully controlled synthetic diet, as in the use of infant formulas by neonates and in TPN

NURSING IMPLICATIONS

Clients Taking Vitamin and Mineral Supplements

1. Nurses can be instrumental in educating the public about an adequate diet and the benefits and hazards of vitamin therapy.

2. Individuals at risk of nutritional deficiencies include pregnant women, infants and children, individuals with eating disorders, persons on fat diets, persons with chronic GI disorders, alcoholics, drug-dependent persons, and the elderly.

3. Nursing assessment includes evaluation of the client’s nutritional status using information from a dietary history, health history, physical examination, and laboratory studies.

4. The absorption of fat-soluble vitamins may be reduced in persons using mineral oil or cholestyramine resin. Mineral oil should not be taken with meals or vitamin supplements.

5. Oral potassium supplements should be taken after meals or with food and with a full glass of water to decrease GI upset.

6. Tablets containing potassium supplements must not be chewed or crushed.

7. Clients taking potassium supplements are monitored for the development of gastrointestinal distress or GI bleeding.

8. Parenteral potassium is infused slowly. Infiltration may be associated with tissue necrosis.

9. Ion exchange resins, such as polystyrene sulfonate (Kayexalate), may be given orally or rectally as a retention enema.

10. Calcium supplements should be taken in divided doses approximately 1 hour after meals. Encourage exposure to sunlight, weight-bearing exercise, and compliance with other medications intended to prevent osteoporosis.

11. Maximum benefit from fluoride supplementation is achieved by chewing and retaining the product in the mouth before swallowing it.

12. Assess the weight, blood pressure, and intake and output of clients receiving TPN. Monitor for the development of complications, such as infection.

13. No drugs are added to the TPN line without prior consultation with the pharmacist to determine possible incompatibilities.

VITAMINS

Vitamins are chemical substances that regulate and/or participate in chemical reactions within the body. They are generally not synthesized in sufficient quantities by the body to supply its needs. This category of nutrients is, perhaps, the most controversial. Although most people believe that vitamins are important and essential for good health, some believe that if a little is good, more is better.