Chapter 9 - Lecture notes 9 PDF

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Chapter 9: Nutrition Basics After completing this chapter, the student will be able to: 1) List the essential nutrients, and describe the functions they perform in the body. 2) Describe the guidelines that have been developed to help people choose a healthy diet, avoid nutritional deficiencies, and reduce their risk of diet-related chronic diseases. 3) Discuss nutritional guidelines for vegetarians and for special population groups. 4)Explain how to use food labels and other consumer tools to make informed choices about foods. 5)Put together a personal nutrition plan based on affordable foods that you enjoy and that will promote wellness, today as well as in the future. Lecture Outline This chapter contains information about the basics of good nutrition, with an emphasis on avoiding diet-related “lifestyle” diseases. I.

Nutritional Requirements: Components of a Healthy Diet A. The body requires proteins, fats, carbohydrates (macronutrients), vitamins, minerals (micronutrients), and water; about 45 essential nutrients must be obtained from food. B.

Fuel potential of food is expressed in kilocalories, 1 kilocalorie representing the amount of heat needed to raise the temperature of 1 liter of water 1 degree Celsius. Most people require about 2,000 kilocalories per day. A kilocalorie is equal to 1,000 calories. We use the term calorie to represent the larger energy unit; the word calorie is also used on food labels. 1.

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2. Alcohol, though not an essential nutrient, also supplies energy, providing 7 calories per gram. Proteins form muscles and bones as well as parts of blood, enzymes, hormones, and cell membranes. They are composed of amino acids. 1.

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3. 4. 5. D.

Of the six classes of essential nutrients, three supply energy: proteins, carbohydrates, and fats— 4 calories per gram for proteins and carbohydrates and 9 calories per gram for fats.

Nine essential amino acids found in food are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Another 11 amino acids can be produced by the body using the building blocks supplied by foods. Protein sources are considered “complete” if they supply all essential amino acids in adequate amounts and “incomplete” if they do not. a. Most animal proteins are complete; most plant proteins, such as legumes and nuts, are incomplete. b. Certain combinations of vegetable proteins generally make up for the missing amino acids in the other protein. Proteins consumed throughout the course of a day form a pool of amino acids from which the body can draw. c. Vegetarians should include a variety of vegetable protein sources in their diet to make sure they get all the essential amino acids in adequate amounts. Most American diets contain more protein than is needed, and two thirds of the protein generally comes from animal sources. The body converts excess protein into fat. Protein intake should make up 10 to 35 percent of total daily calorie intake, depending on the individual’s age. Adequate daily intake of protein for adults is 0.8 gram per kilogram of body weight.

Fats, or lipids, are the most concentrated source of energy ; they represent stored energy and provide insulation and support for body organs. 1. Fats help absorb fat-soluble vitamins and fuel the body during rest and light activity. Two fats, linoleic acid and alpha-linoleic acid, are essential to regulating such body functions as blood pressure and contribute to healthy pregnancy. 2.

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. a. Within a triglyceride, different fatty acid structure results in different types of fats. Depending on this structure, a fat may be unsaturated, monounsaturated, polyunsaturated or saturated. Essential fatty acids, linoleic and alpha-linolenic acids are both polyunsaturated. Different types of fatty acids have different characteristics and different effects on health.

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c. d. e. 3.

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Liquid oils tend to be unsaturated, and solid fats are mostly saturated. (1) 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. (2) Unsaturated fats 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. Palm and coconut oils are highly saturated, while fish oils are mostly polyunsaturated. 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. Hydrogenation also changes some unsaturated fatty acids to trans fatty acids. Four American cities, including New York and Philadelphia, have banned artificial trans fats in restaurants. In California, a statewide ban takes effect in 2010–2011.

Different types of fats have different effects on health. a. Saturated and trans fatty acids raise low-density lipoproteins (LDL). In large amounts, trans fatty acids may lower high-density lipoproteins (HDL). Saturated fats have been found to impair the ability of HDLs to prevent inflammation of blood vessels, one of the key factors in vascular disease. b. Unsaturated fatty acids lower LDL. c. Monounsaturated fatty acids may also increase levels of HDL, providing benefits for heart health. d. Trans fats have a double negative effect on the heart by both raising LDL and reducing highdensity lipoproteins. (1) To reduce saturated fat, reduce the intake of meat and full-fat dairy products (whole milk, cream, butter, cheese, and ice cream). (2) To reduce trans fats, reduce the intake of deep-fried foods and baked goods made with hydrogenated vegetable oils; use liquid oils for cooking; and choose tub or squeeze margarines over stick margarine.

(3) Since January 2006, food labels have included trans fat content. e. When used in place of saturated fats, monounsaturated fatty acids improve cholesterol levels and may protect against some cancers. f. Omega-3 fatty acids, a form of polyunsaturated fat found primarily in fish, benefit health by reducing the tendency of blood to clot, inhibiting inflammation and abnormal heart rhythms, and reducing blood pressure and risk of heart attack in some people. Nutritionists recommend consuming fish two or more times a week. g. Foods rich in omega-3s contain the essential nutrient alpha-linolenic acid h. Omega-6 fatty acids, another form of polyunsaturated fat, represent most of the polyunsaturated fats consumed by Americans. Some nutritionists recommend reducing the proportion of omega-6s in favor of omega-3s. 4. Other health effects of a high-fat diet include weight gain and increased risk of certain cancers. 5. Experts recommend that total fat intake make up 20 percent to 35 percent of total calories. In reducing fat intake, the emphasis should be on choosing unsaturated fats instead of saturated and trans fats. Carbohydrates supply energy to the brain, nervous system, and blood, as well as provide fuel for high-intensity exercise. 1. 2. 3. 4.

If we do not consume enough carbohydrates, we synthesize them from proteins; in rare occurrences when both are lacking, the body breaks down the proteins in its own vital organs. Simple carbohydrates include sucrose, fructose, maltose, and lactose. Complex carbohydrates include starches and most types of dietary fiber. Starches and most types of dietary fiber are complex carbohydrates. Whole grains are unrefined grains. Refined carbohydrates such as white flour and white rice a. tend to be much lower in fiber, vitamins, minerals, and other beneficial compounds. Many refined grain products are enriched and fortified with vitamins and minerals, but often the nutrients lost in processing are not replaced.

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Unrefined carbohydrates take longer to digest and keep blood sugar and insulin levels low , which may reduce the risk of diabetes, heart disease, high blood pressure, stroke, and certain forms of cancer. Digestion breaks down starches and double sugars into glucose for absorption. In the bloodstream, glucose is used by cells for energy, and the liver and muscles take up glucose in the form of glycogen for carbohydrate storage. Insulin and glucose levels rise and fall after a meal or snack containing any type of carbohydrate. a. Some foods cause a quick and dramatic rise in glucose and insulin levels; others have slower, more moderate effect. b. A food that has a strong effect on blood glucose levels is said to have a high glycemic index. Some research suggests that consuming foods with a high glycemic index may increase appetite and also increase risk of diabetes and heart disease. (1) Although refined complex carbohydrates and high-fiber foods generally tend to have a low glycemic index, patterns are less clear for other types of foods and do not follow an easy distinction such as that of simple versus complex carbohydrates. (2) This complexity is one reason why major health organizations have not issued specific guidelines for glycemic index.

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Americans consume 200 to 300 grams of carbohydrates daily, well above the 130 grams needed to meet dietary needs. Health experts advise consuming 45 percent to 65 percent of total calories as carbohydrates. They also advise reducing added sugars to 10 percent of total daily calories. Fiber includes plant substances that are difficult or impossible for humans to digest. Dietary sources of fiber include fruits, legumes, oats, and psyllium. 1.

Dietary fiber is the nondigestible carbohydrates that are present naturally in grains, legumes, and vegetables.

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Functional fiber is nondigestible carbohydrates that have either been isolated from natural sources or synthesized in a lab and then added to a food or dietary supplement.

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Fruits, legumes, oats, barley, wheat, other grains and cereals, and vegetables are good sources of fiber. Experts recommend a daily fiber intake of 38 grams for adult men and 25 grams for adult women.

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A diet high in fiber can help reduce the risk of type 2 diabetes and heart disease as well as improve gastrointestinal health.

Vitamins are organic substances required in small amounts to regulate various processes within living cells. 1. Thirteen vitamins are essential to health. Four are fat-soluble (A, D, E, and K), and nine are watersoluble (C and 8 B-complex vitamins: thiamine, riboflavin, niacin, B-6, folate, B-12, biotin, and pantothenic acid). a. Water-soluble vitamins are absorbed directly into the bloodstream ; excess water-soluble vitamins are excreted in urine. b. Fat-soluble vitamins are stored in the liver and in fat tissues rather than excreted. 2. Some vitamins help chemical reactions take place; they unleash energy stored in carbohydrates, proteins, and fats. They are critical in producing red blood cells and in maintaining the nervous, skeletal, and immune systems. 3. Some vitamins act as antioxidants, which help preserve healthy cells in the body . These include vitamins C and E, as well as beta carotene, which is a derivative of vitamin A. 4. Vitamins are found in fruits, vegetables, and grains and are added to some processed foods. 5. Vitamin-deficiency diseases are rare in the United States because vitamins are readily available from our food supply. Alcoholics run the greatest risk. a. Low intake of folate and vitamins B-6 and B-12 has been linked to increased heart disease risk. b. Many Americans consume less than recommended amounts of vitamins A, C, and B-6. Fifty percent of adult Americans do not get the recommended amount of Vitamin D. c. Scurvy is a potentially fatal illness caused by a deficiency of Vitamin C. d.

Vitamin D deficiency has been linked to children’s development of disabling bone deformations from rickets. New research is now linking vitamin D deficiency with an increased risk of cardiovascular disease in adults as well as certain types of breast cancer in women.

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Some vitamins can be harmful if taken in excess . It is best to obtain vitamins from food rather than relying on supplements.

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The nutrient value of vegetables is best retained if they are consumed when as fresh as possible and are not overcooked. Minerals are inorganic elements required in small amounts to help regulate body functions, aid growth in maintenance of body tissues, and act as catalysts for energy release. There are about 17 essential minerals. 1. Major minerals that the body needs in amounts of 100 milligrams or more per day include calcium, phosphorus, magnesium, sodium, potassium, and chloride. 2. Essential trace minerals include copper, fluoride, iodide, iron, selenium, and zinc. 3. Minerals most commonly lacking in our diets are calcium, iron, and zinc ; magnesium is occasionally lacking. Lean meats are rich in iron and zinc; low-fat or skim milk provides calcium. Plant foods are good sources of magnesium. Water is the major component in food and in the human body. 1.

The body is 50 percent to 60 percent water; the need for water is greater than the need for any other nutrient.

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Water is distributed throughout the body in lean tissues, other tissues, and body fluids. Water is necessary for digestion and absorption; it is the medium in which chemical reactions take place. 4. Foods and fluids consumed provide 80 to 90 percent of daily intake; the rest is generated through metabolism. 5. Water is lost through urine, feces, and sweat and through evaporation from the lungs. 6. Most people can maintain a healthy water balance by consuming beverages at meals and drinking fluids in response to thirst. 7. To maintain hydration, all fluids, including those containing caffeine, can count toward your total fluid intake. Under these guidelines, men need 3.7 total liters, with 3.0 liters (13 cups) coming from beverages. Women need 2.7 liters, with 2.2 liters (9 cups) coming from beverages. Many substances in food are not essential nutrients but may affect health. 1. Free radicals, substances that damage cells and mutate genes, have been implicated in aging, cancer, and cardiovascular and other degenerative diseases. Some antioxidants prevent or reduce the formation of free radicals; others remove free radicals from 2. the body. Antioxidants can repair some types of free radical damage. 3. Fruits and vegetables are good sources of antioxidants such as vitamins C and E and selenium. 4. Antioxidants are a particular type of phytochemical, a substance found in plant foods that may help prevent chronic disease.

Nutritional Guidelines: Planning the Diet A. Dietary Reference Intakes (DRIs), the Dietary Guidelines for Americans, and the USDA MyPyramid food guidance system are standards to help people design healthy diets and prevent diet-related chronic illness. 1. DRIs, introduced in 1997, have a broader focus than the earlier standards, called the Recommended Dietary Allowances (RDAs). DRIs are frequently reviewed and updated. a. DRIs consider prevention of nutrient deficiencies , as did the RDAs, as well as the role of nutrients in promoting optimal health and preventing chronic diseases such as cancer, osteoporosis, and heart disease. b. DRIs include standards for both recommended intakes and maximum safe intakes. c. d.

Recommended intake is expressed as an RDA or Adequate Intake (AI). An AI is set when there is insufficient information to set an RDA value.

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Regardless of the type of standard used, the DRI is the best available estimate of intake for optimal health.

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The Tolerable Upper Intake Level (UL) sets the maximum daily intake by a healthy person that is unlikely to cause health problems. Due to lack of data, ULs have not been set for all nutrients.

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There is no established benefit from consuming nutrients at levels above the RDA or AI. The aim of DRIs is to help people meet their nutritional needs primarily through food, rather than vitamin supplements.

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Recommended dosages for some essential nutrients have not been established. Some vitamins and minerals are dangerous when ingested in excess. Large doses also may affect the absorption of other vitamins and minerals. The Food and Drug Administration Daily Values are standards for fat, cholesterol, carbohydrate, dietary fiber, and selected vitamins and minerals. The values represent intake levels for a 2,000-calorie diet.

To provide general guidance for choosing a healthy diet, the USDA and the Department of Health and Human Services jointly issued dietary guidelines in 2010. These guidelines are intended for healthy children age 2 years and older and adults of all ages. Key recommendations include the following: 1. Consume a variety of nutrient-dense foods within and among the basic food groups, while staying within energy needs. a. Two eating plans that translate nutrient recommendations into food choices are the USDA MyPlate and the DASH eating plan. b.

2.

To follow these eating plans, many Americans would have to make some general dietary changes by eating more dark green vegetables, orange vegetables, legumes, fruits, whole grains, and low-fat and fat-free milk and milk products. c. Americans would also have to eat less refined grains, saturated fat, trans fat, cholesterol, added sugars, and calories. Control calorie intake to manage body weight. a.

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Overweight and obesity are major public health problems in the United States. Calorie intake and physical activity both work together to influence body weight. b. Evaluate your body weight in terms of body mass index (BMI), a measure of relative body weight that also takes height into account. c. When trying to lose weight , calorie count should never fall below 1,800 cal/day for men and 1,200 cal/day for women. Increase daily intake of foods from certain groups: fruits and vegetables, whole grains, and fat-free or low-fat milk and milk products. a. Fruits and vegetables are important sources of dietary fiber, vitamins, and minerals. Eat a variety of fruits—fresh, frozen, canned, or dried—rather than fruit juice for most of your choices. b. c.

Eat more dark green vegetables, orange vegetables, and legumes. Whole grains provide more fiber and nutrients than refined grains , and intake of whole grains reduces the risk of chronic disease and helps with weight maintenance.

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Milk and other dairy products are important sources of calcium and other nutrients . Regular consumption can reduce the risk of low bone mass throughout life and helps to control calorie intake and reduce intake of saturated fat and cholesterol. Yogurt and lactose-free milk are options for people who are lactose intolerant. Non-dairy calcium sources are available to individuals who avoid all milk products. Choose fats wisely, limiting intake of saturated and trans fats. a. b.

c. d.

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Fats and oils provide essential fatty acids needed for a healthy diet. The type and amount of fats consumed can make a difference for health. A diet low in saturated fat, trans fat, and cholesterol helps keep blood cholesterol low and reduces the risk for heart disease. Most fats in the diet should come from sources of unsaturated fats, such as fish, nuts, and vegetable oils. A diet containing omega-3 fats from fish also reduces the risk of heart disease. If you need to reduce your cholesterol intake, limit your intake of foods that are particularly high in cholesterol, including eggs yolks, dairy fats, certain shellfish, a...