Nutrition Basics This topic examines the role of personal dietary choices and the basic principles of nutrition. It introduces the six classes of essential nutrients and explains their roles in health and disease. It also provides guidelines for designing a healthy diet plan. I. Components of a Healthy Diet A. The body requires proteins, fats, carbohydrates, vitamins, minerals, and water; about 45 essential nutrients must be obtained from food. 1. The body needs some essential nutrients in relatively large amounts. These macronutrients include proteins, fats, carbohydrates, vitamins, minerals, and water. 2. The body needs micronutrients, such as vitamins and minerals, in much smaller amounts. B. Most nutrients become available to the body through the process of digestion, in which food is broken down and processed for use for normal body functions. C. The amount of energy in food is expressed in kilocalories (kcal). 1. 1 kilocalorie represents the amount of heat needed to raise the temperature of 1 liter of water 1 degree Celsius. a. An average person requires about 2000 kilocalories per day. b. The difference between energy and calories is that energy is the capacity to do work and calories are used to measure energy. 2. Of the six classes of essential nutrients, fat supplies the most energy per gram (9 calories) followed by protein and carbohydrate (4 calories per gram). a. Alcohol, though not an essential component of our diet, also supplies energy, providing 7 calories per gram. b. It is important to consume calories wisely, concentrating on nutrient-dense foods. D. Proteins—The Basis of Body Structure 1. Proteins form muscles and bones as well as parts of blood, enzymes, hormones, and cell membranes. 2. Amino Acids a. Amino acids are the building blocks of proteins. b. Twenty common amino acids are found in food proteins. i. Nine amino acids are essential. ii. As long as foods supply certain nutrients, the body can produce the other 11 amino acids. 3. Complete and Incomplete Proteins a. Protein sources are considered “complete” if they supply all essential amino acids in adequate amounts and “incomplete” if they do not. b. Most animal proteins are complete; most plant proteins, such as legumes and nuts, are incomplete. c. Certain combinations of vegetable proteins generally make up for the missing amino acids in the other protein.4. Recommended Protein Intake a. Adequate daily intake of protein for adults is 0.8 gram per kilogram of body weight. b. Most American diets contain more protein than is needed. i. The body converts excess protein into fat. c. The Acceptable Macronutrient Distribution Range (AMDR) for protein intake is 10% to 35% of total daily calorie intake, depending on the individual’s age. E. Fats—Essential in Small Amounts 1. Fats, or lipids, are the most concentrated source of energy; they represent stored energy and provide insulation and support for body organs. a. Fats provide 9 calories of energy per gram. b. Fats help absorb fat-soluble vitamins and fuel the body during rest and light activity. 2. Two fats, linoleic acid and alpha-linolenic acid, are essential to regulating such body functions as blood pressure and contribute to healthy pregnancy. 3. Types and Sources of Fats a. Most of the fats in food are similar in composition, including a glycerol molecule plus three fatty acids. The resulting structure is called a triglyceride. i. Within a triglyceride, different fatty acid structures result in different types of fats. A fat may be: (1) Unsaturated or saturated (2) Monounsaturated (3) Polyunsaturated b. The essential fatty acids linoleic and alpha-linolenic acids are both polyunsaturated. c. Different types of fatty acids have different characteristics and different effects on health. i. Liquid oils tend to be unsaturated, and solid fats are mostly saturated. ii. Saturated fats are usually solid at room temperature. Leading sources of saturated fat are red meats (hamburger, steak, roasts), whole milk, cheese, and hot dogs or luncheon meats. d. Most monounsaturated and polyunsaturated fatty acids are liquid at room temperature. Olive, canola, safflower, and peanut oils contain mostly monounsaturated fatty acids; corn, soybean, and cottonseed oils contain mostly polyunsaturated fatty acids. 4. Hydrogenation and Trans Fats a. Hydrogenation turns unsaturated fatty acids into more-solid fats to extend shelf life and prevent separation of fatty oil. These solid fats are highly saturated. b. Hydrogenation also changes some unsaturated fatty acids to trans fatty acids. It is done to transform liquid oil into margarine or vegetable shortening. i. Trans fats have been associated with an increase in low-density lipoprotein (LDL) cholesterol (“bad” cholesterol) and a lowering of high-density lipoprotein (HDL) cholesterol (“good” cholesterol). 5. Recommended Fat Intake a. To meet the body’s demand for essential fats: i. Men need 17 grams of linoleic acid and 1.6 grams of alpha linolenic acid per day.ii. Women need 12 grams of linoleic acid and 1.1 grams of alpha-linolenic acid per day. b. Most Americans consume enough essential fats; limiting unhealthy fats is a much greater health concern. c. The AMDR for total fat intake is 20% to 35% of total calories. i. Omega-6 fatty acids (5–10% of total calories) ii. Omega-3 fatty acids (0.6–1.2% of total calories) d. It is important to evaluate fat content, but more important to look at it in the context of one’s overall diet. e. The latest federal guidelines place greater emphasis on choosing healthy unsaturated fats in place of saturated and trans fats. F. Carbohydrates—An Important Source of Energy 1. Carbohydrates supply energy to the brain, nervous system, and blood, as well as provide fuel for high-intensity exercise. 2. Simple and Complex Carbohydrates a. Simple carbohydrates add sweetness to foods and include single sugar molecules (monosaccharides) and double sugar molecules (disaccharides). i. Monosaccharides include: (1) Glucose—most common sugar used by animals and plants for energy (2) Fructose—a very sweet sugar found in fruits (3) Galactose—the sugar found in milk ii. Disaccharides are pairs of single sugars. (1) Sucrose or table sugar (fructose + glucose) (2) Maltose or malt sugar (glucose + glucose) (3) Lactose or milk sugar (galactose + glucose) b. Complex carbohydrates include starches