This Document Contains Chapters 5 to 6 CHAPTER 5 LIPIDS OVERVIEW This chapter describes the four classes of lipids: fatty acids, triglycerides, phospholipids, and sterols. The basic structure of fatty acids is described and essential fatty acids are discussed, including dietary recommendations and food sources. Current research related to omega-3 fatty acids is emphasized. Structure, functions, and roles in the body are part of the triglyceride presentation. The roles of phospholipids and sterols, particularly cholesterol, are mentioned. A detailed description of where fat is found in foods is presented, including how to find hidden fats and how fat replacements are used. A general explanation of fat digestion and absorption is provided. Lipid transport is discussed including chylomicrons, and high-, low-, and very low-density lipoproteins. Brief additional discussions include the contribution of fat to satiety, flavor, and texture of foods; fat rancidity; and medical interventions to lower blood lipids. Recommendations for fat intake are outlined, including those from the American Heart Association, the National Cholesterol Education Program, the Food and Nutrition Board, and the 2010 Dietary Guidelines for Americans. The Nutrition and Your Health section illustrates the roles fat, cholesterol, and lipoproteins play in the development or prevention of cardiovascular disease. KEY TERMS Alpha-linolenic acid Antioxidant Arachidonic acid Atherosclerosis BHA and BHT Cerebrovascular accident (CVA) Cholesterol Chylomicron Cis fatty acid Diastolic Blood Pressure Diglyceride Docosahexaenoic acid (DHA) Eicosanoids Eicosapentaenoic acid (EPA) Emulsifier Essential fatty acids Foam cells Glycerol Hemorrhagic stroke High-density lipoprotein (HDL) Hydrogenation Lecithin Linoleic acid Lipase Lipoprotein Lipoprotein lipase Long-chain fatty acid Low-density lipoprotein (LDL) Menopause Monoglyceride Monounsaturated fatty acid Myocardial infarction Oleic acid Omega-3 fatty acid Omega-6 fatty acid Oxidize Phospholipid Plaque Polyunsaturated fatty acid Rancid Saturated fatty acid Scavenger cells Sterol Systolic Blood Pressure Total parenteral nutrition Trans fatty acid Triglyceride Very low-density lipoprotein (VLDL) STUDENT LEARNING OUTCOMES Chapter 5 is designed to allow you to: 5.1 Understand the common properties of lipids. 5.2 List three structural forms of lipids (fats) and the role of each in our food supply. Distinguish between fatty acids and triglycerides. Discuss the importance of essential fatty acids, as well as the balance between omega-3 and omega-6 fatty acids, with respect to health. 5.3 Differentiate among food sources of saturated, monounsaturated, and polyunsaturated fatty acids and cholesterol. 5.4 Explain how lipids are digested and absorbed. 5.5 Name the classes of lipoproteins and classify them according to their functions. 5.6 List the function of lipids, including the roles of phospholipids and the functions of cholesterol in the body. 5.7 Explain the recommendations for fat intake. 5.8 Characterize the symptoms of cardiovascular disease and highlight some known risk factors. LECTURE OUTLINE 5.1 Lipids: Common Property: do not readily dissolve in water 5.2 Lipids: Triglycerides, Phospholipids, and Sterols A. Overview 1. Lipids are fats (solid at room temperature) and oils (liquid at room temperature). 2. Chemical structures vary. 3. Composed of carbon, hydrogen and oxygen 4. Energy yield: 9 kcal/g B. Fatty Acids and Triglycerides 1. Fatty acids are found in triglyceride, which is glycerol bonded to three fatty acids. 2. General structure a. Chain of carbons bonded together and flanked by hydrogens b. The alpha end contains an acid c. The omega end is a methyl group 3. Fat in food is a mixture of many different fatty acids. Fats and oils are classified as saturated, monounsaturated, or polyunsaturated, based on type of fatty acids present in greatest concentration. (see Fig. 5-3) 4. Each carbon atom can form four bonds 5. Saturated fatty acids a. Each carbon in the chain is saturated by four hydrogens (see Fig. 5-1a) b. Solid at room temperature c. Mostly animal fats d. Saturated fats in whole milk are suspended in liquid 6. Unsaturated fatty acids a. Contain at least 1 double bond, so at least 2 carbons are not saturated with hydrogens b. Double bonds create kinks in structure making them less stable, packing together less closely, which results in liquid state at room temperature. c. Monounsaturated fatty acids 1) One double bond (see Fig. 5-1b) 2) Canola and olive oils are high in monounsaturated fatty acids d. Polyunsaturated fatty acids 1) Two or more double bonds (see Fig. 5-1 c and d) 2) Corn, soybean, sunflower, and safflower oils are rich in polyunsaturated fatty acids e. Structural forms of fatty acids f. Cis fatty acids 1) Natural form of mono- and polyunsaturated fatty acids 2) Hydrogen atoms on the same side of the carbon-carbon double bond (see Fig. 5-2) 3) Chemical structure of bonds allows fatty acid to bend (thus liquid at room temperature) g. Trans fatty acids 1) Found naturally as conjugated linoleic acid or created synthetically by hydrogenation process 2) Hydrogens are positioned (naturally or synthetically) on opposite sides of the double bond in the fatty acid chain (see Fig. 5-2) 3) Chemical structure of bonds straightens the chain, giving it characteristics like a saturated fat (more solid at room temperature). 4) Trans fats should be minimized in the diet. 5) Some naturally-occurring trans fats (conjugated linoleic acid) may be health benefits. a) Found in beef, milk, and butter b) Improve insulin levels in diabetics c) Decrease risk of heart disease, cancer, and obesity h. Unsaturation increases susceptibility to react with active oxygen molecules. 1) Occurs in food and body 2) In body: causes inflammation and tissue damage leading to aging, atherosclerosis, and cancer 3) Antioxidants (i.e., Vitamin E and C) combat oxidation reactions. 7. Chain length affects fatty acid characteristics a. Most long-chain, saturated fats are solid at room temperature b. Monounsaturated fats, regardless of length, are liquid at room temperature c. Most fats in the body and food are long-chain 8. Location of the first double bond is important a. Omega-3 (ω3) fatty acid (see Fig. 5-1c) 1) First double bond is 3 carbons from the methyl (omega) end 2) Alpha-linolenic acid b. Omega-6 (ω6) fatty acid (see Fig. 5-1b) 1) First double bond is 6 carbons from the methyl end 2) Linoleic acid c. Linoleic acid and alpha-linolenic acid are both essential fatty acids (not made by the body; must be consumed in the diet) d. Omega-9 fatty acid 1) First double bond is 9 carbons from the methyl end 2) oleic acid 9. The essential fatty acids (EFAs) a. Only certain polyunsaturated fatty acids are essential: Alpha linolenic acid (omega 3 fatty acid) and Linoleic acid (omega-6 fatty acid) (see Fig. 5-4) 1) Functions: immune system function and vision, help form cell membranes, produce eicosanoids 2) Must consume from diet (from plant sources) as body cannot make these fatty acids b. Long chain omega 3 fatty acids: eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) 1) Created from EFA, alpha linolenic acid (omega 3 fatty acid) 2) Roles in brain and nervous system 3) EPA function: role in brain and nervous system, important for concentration and vision, and converted to an anti-inflammatory agent 4) DHA function: brain and nervous system, important during pregnancy for the fetal brain and nervous system development 5) Dietary intake requirement a) Conversion of EFA inadequate b) Two servings fatty fish/week 6) Sources a) Fatty fish such as salmon, tuna, sardines, anchovies, striped bass, catfish, herring, mackerel, trout, and halibut b) Oils such as canola and soybean c) Nuts such as walnuts, chia seeds, and flax seeds d) EPA/DHA supplement also an option c. Daily intake requirement for EFAs 1) 5% total kcal/day 2) 2-4 Tbsp of plant oil per day 3) Sources: Plant oils (canola and flax seed), nuts, seeds, vegetables, whole-grain breads, and cereals 4) Excessive intake: may cause uncontrolled bleeding and hemorrhagic stroke d. Effects of a deficiency of essential fatty acids 1) Flaky itchy skin 2) Diarrhea 3) Restricted growth and wound healing 4) Infections 5) Seen in people on total parenteral nutrition containing little fat for 2–3 weeks e. Long chain omega-6 fatty acid: Arachidonic acid (AA) 1) Created from EFA, linoleic acid (omega-6 fatty acid) 2) Acts as pro-inflammatory agent and can contribute to inflammatory conditions if consumed in excess f. Health effects of omega 3 fatty acids 1) 2 to 4 g/day from fish 2) Lower blood triglycerides 3) Management of pain of inflammation with rheumatoid arthritis 4) Improvement of mild depression 10. Triglycerides a. Most common fat/oil found in foods b. Most fats in the body are triglycerides c. Structure 1) Glycerol backbone with 3 fatty acids attached (see Fig. 5-5a) 2) Monoglyceride has 1 fatty acid attached to the glycerol 3) Diglyceride has 2 fatty acids attached to the glycerol d. Most fats are absorbed as monoglycerides and free fatty acids; once absorbed, they are re-formed into triglycerides C. Phospholipids 1. Glycerol backbone with two fatty acids and 1 compound containing phosphorous (see Fig. 5-5b) 2. Important part of cell membrane 3. Participate in fat digestion 4. Body is able to produce them; no dietary requirement 5. Lecithin is a phospholipid D. Sterols 1. Multi-ringed structure (see Fig. 5-5c) 2. Waxy substance that does not dissolve in water 3. Cholesterol is an example a. Incorporated into all cell structures b. Used to form some hormones and bile c. Body can make all the cholesterol it needs; no dietary requirement 5.3 Fats and Oils in Foods A. Overview 1. Fat percentages of various foods a. Foods containing approximately 100% of energy as fat 1) Salad oils 2) Butter 3) Margarine 4) Mayonnaise b. Foods containing approximately 80% fat 1) Nuts 2) Bologna 3) Avocados 4) Bacon c. Foods containing approximately 75% fat 1) Peanut butter 2) Cheddar cheese d. Foods containing approximately 40% to 60% fat 1) Meats 2) Whole dairy 3) Doughnuts 2. Figure 5-6 shows sources of fat from MyPlate while Figure 5-7 shows examples of food sources of fat 3. Major lipids and food examples a. Saturated fatty acids: animal fats b. Unsaturated/essential fatty acids: plant oils c. Phospholipids: egg yolks, wheat germ, peanuts, soybeans, organ meats, and additives (e.g., lecithin) that function as emulsifiers (see Fig. 5-8) d. Cholesterol: found only in animal foods B. Fat Is Hidden in Some Foods 1. Use the Nutrition Facts labels to find hidden fats (see Fig. 5-9) a. Ingredients are listed by order of weight in the product b. Look for animal fats (bacon beef, ham, lamb, pork, chicken, turkey fats), lard, nuts, dairy fat (butter and cream), vegetable oils, and partially hydrogenated shortening or vegetable oil in the ingredients list 2. Understand definitions of claims on labels regarding fats a. "Low-fat" means less than 3 grams of fat per serving b. "Fat-free" means less than 0.5 grams fat per serving c. "Reduced-fat" means product has at least 25% less fat than is usually found in the food 3. Consume diet rich in fruits and vegetables, and whole grains to achieve a low fat diet easily C. Fat in Food Provides Some Satiety, Flavor, and Texture 1. High-fat meals are high-calorie meals 2. Fat adds body, tenderness, and smooth texture to foods 3. Many flavorings dissolved in fat 4. Heating spices in oils intensifies flavors D. Low-Fat Diets 1. Switching from high-fat to low-fat diet can take adjustment 2. Tastes and preferences eventually change 3. Reduction in chronic disease risk can be a benefit E. Fat replacement strategies for foods 1. When fat is removed, sugar usually replaces it, making it similar in energy density 2. To reduce your fat intake and still have the mouth feel of fat, low-fat food products are being developed 3. Manufacturers replace fat with: a. Water b. Protein: Simplesse® and Dairy-Lo® c. Starch derivatives: Z-trim® d. Fiber: Matrin®, Stellar®, Oatrim® e. Gums 4. Engineered fats and related products a. Olestra (Olean®) and salatrim (Benefat®): fatty acids are synthetically bound to sucrose b. Cannot be digested by human enzymes or bacteria in gut c. Not absorbed F. Fat rancidity limits shelf life of foods 1. Double bonds of unsaturated fats break down, producing disagreeable odor and flavor 2. Breakdown of fats is driven by ultraviolet light, oxygen, some processing methods (i.e., heat) 3. Saturated and trans fats are less susceptible to rancidity 4. Foods most likely to become rancid include deep-fried foods, food with large amount of exposed surface, foods high in polyunsaturated fats 5. Manufacturers seek to prolong shelf life with: a. Use of partially hydrogenated (trans) fats b. Addition of antioxidants (e.g., vitamin E, BHA, and BHT) c. Air-tight seal G. Hydrogenation of Fatty Acids in Food Production Increases Trans Fatty Acid Content 1. Benefits of solid fats in food production a. Increased shelf life b. Flavor and mouth feel (e.g., flaky pie crusts) 2. Partial hydrogenation converts some double bonds into single bonds, making fats semi-solid at room temperature (see Fig. 5-10) 3. Cis fatty acids: hydrogens exist on the same side of the double bond, causing a bend in the carbon chain of the fatty acid 4. Trans fatty acids: hydrogens exist on opposite sides of the double bond, leaving a straighter carbon chain that resembles a saturated fatty acids 5. Trans fats are associated with negative health effects a. Increase blood cholesterol b. Increase inflammation 6. FDA requires listing of trans fat content on food labels 7. 2010 Dietary Guidelines for Americans recommends minimal trans-fat intake 8. American Heart Association advises limiting trans-fat intake to 139/89) 5. Diabetes 6. Other risk factors: a. Low HDL ( 55 years for women; > 45 years for men) c. Family history d. High fasting triglycerides (> 200 mg/dl) e. Obesity (android, especially) f. Inactivity 7. Inadequate intakes of vitamin B-6, folate and vitamin B-12 may lead to increased homocysteine levels, which damage blood vessels 8. Metabolic syndrome also raises risk D. Medical Interventions to Lower Blood Lipids 1. Goal of medical therapy: decrease LDL to 190 mg/dl c. Age 40-75 with LDL 70-189 mg/dl and diabetes d. Age 40-75 with LDL 70-189 mg/dl and greater than 7.5% risk for atherosclerotic CVD within the next 10 years 3. Medications a. Reduce production of cholesterol by liver (statins) b. Reduce absorption of bile acids from intestine c. Reduce triglyceride production by liver E. Plant Sterols for Cardiovascular Disease 1. Food products or pills containing plant stanols/sterols reduce cholesterol absorption in the small intestine and reduce specifically LDL 2. Corowise® leading brand of plant sterols 3. FDA approved health claim: Foods containing at least 0.4g grams per serving of plant sterols eaten twice/day with meals for a daily intake of 0.8 g/day as part of diet low in saturated fat and cholesterol, may reduce risk of heart disease. 4. Smart Balance® margarines and Minute Maid HeartWise® 5. Naturally found in nuts, wheat germ, sesame seeds, pistachios, sunflower seeds F. Surgical Treatment for Cardiovascular Disease 1. Percutaneous transluminal coronary angioplasty (PTCA) involves use of a balloon catheter to break apart a blockage, usually followed by placement of a stent to hold the artery open 2. Coronary artery bypass graft (CABG) involves removal of the blocked artery followed by grafting of a blood vessel from another part of the body (usually the leg) BEST PRACTICES: TEACHING STRATEGIES, DEMONSTRATIONS, ACTIVITIES, ASSIGNMENTS, AND MORE 1. Ask students to complete the Rate Your Plate, Is Your Diet High in Saturated and Trans Fat?, activity for this chapter. Use this as a spring board to discuss limiting intake of saturated and trans fats. 2. Ask students to complete the Rate Your Plate, Applying the Nutrition on Facts Label to Your Daily Food Choices, activity for this chapter. Use it to promote a discussion of the fat components listed on the Nutrition Facts label. 3. Have students go to a supermarket and compare the P/S ratio of butter and different margarines, including stick, tub, and squeezable. They can calculate the P/S ratio simply by dividing the grams of saturated fat into those of polyunsaturated fat. Have them report the brands of margarine with the highest P/S ratio. Also, have them collect information on the type of oil used in each of the brands. Use this activity as a springboard to discuss types of margarines and oils to use to lower the risk of coronary heart disease, as well as hydrogenation. 4. In class, compare different fats used in oil products sold in the supermarket and describe the differences in saturation. 5. Have students go to a supermarket and compare various meats for fat grams per serving. They should compare ground turkey, turkey hot dogs, chicken breasts, breaded chicken breasts, ground beef, and various brands of lunchmeats by looking at the food labels. Have students share with classmates what they found. For example, were the poultry products lower in fat grams per serving than red meats? Did breaded products contain the most fat grams per serving? What percentage of lunchmeats were fat? 6. Bring coffee whiteners, whipped toppings, peanut butter, and mayonnaise labeled "no cholesterol" to class. Describe the amount of fat and type of fat in each, illustrating differences in the concepts of cholesterol and fat. 7. Have students purchase a T-Factor Diet Fat Gram Counter from an area bookstore or require it as a course book in your campus bookstore. Have them tally fat grams they eat for a day using this tool. Have them, on a prescribed day, report their total verbally. Use this as a springboard to discuss ways of reducing fat intake. CHAPTER 6 PROTEINS OVERVIEW This chapter introduces amino acids and the basic structure and organization of proteins. Essential, nonessential, and conditionally essential amino acids are differentiated. The digestion and absorption of proteins are explored. The biological functions of protein in producing body constituents; hormones and enzymes; maintaining fluid and acid-base balance; immune function; forming glucose; and its uses as an energy source are detailed. The Recommended Dietary Allowance for protein is discussed. Dietary recommendations for protein intake include comments regarding risks associated with high protein intakes and the importance of dietary plant proteins. Protein content in foods is listed. Protein-energy malnutrition is described along with appropriate prevention and treatment. The Nutrition and Your Health section addresses plant sources of protein and vegetarianism. KEY TERMS Amino acid Branched-chain amino acids Buffers Capillary bed Complementary proteins Conditionally essential amino acids Denaturation Edema Essential amino acids Extracellular space Fruitarian Gruels High-quality (complete) proteins Kwashiorkor Lactoovovegetarian Lactovegetarian Limiting amino acid Lower-quality (incomplete) proteins Marasmus Negative protein balance Nonessential amino acids Pepsin Peptide bond Polypeptide Positive protein balance Preterm Protein Protein-calorie malnutrition (PCM) Protein equilibrium Protein turnover Satiety Sickle cell disease Trypsin Urea Vegan STUDENT LEARNING OUTCOMES Chapter 6 is designed to allow you to: 6.1 Distinguish between essential and nonessential amino acids and explain why adequate amounts of each of the essential amino acids are required for protein synthesis. 6.2 Describe how amino acids form proteins. 6.3 Identify food sources of protein, distinguish between high-quality and low-quality proteins, and describe the concept of complementary proteins. 6.4 Describe how protein is digested, absorbed, and metabolized in the body. 6.5 List the primary functions of protein in the body. 6.6 Apply current recommendations for protein intake to determine protein needs for healthy adults. 6.7 Describe the harmful effects of a high--protein diet and describe what is meant by positive protein balance, negative protein balance, and protein equilibrium. 6.8 Describe how protein-calorie malnutrition eventually can lead to disease in the body. 6.9 Develop vegetarian diet plans that meet the body’s nutritional needs. LECTURE OUTLINE 6.1 Amino Acid—Building Blocks of Proteins A. Overview 1. North American diets are rich in protein 2. Proteins are made up of carbon, hydrogen, oxygen, and nitrogen (see Fig. 6-1) 3. Regulate and maintain body functions, fluid balance, hormone and enzyme production, visual processes, transport, and cell repair 4. Inadequate consumption leads to slowdown of metabolic processes. 5. Provide 4 kilocalories per gram 6. Amino acids are the building blocks of proteins a. Basic structure includes amino group, acid group, and side (R) group b. Branched chain amino acids (leucine, isoleucine, and valine) can be used to fuel muscle during exercise c. There are 20 different amino acids (see Table 6-1) 1) There are 11 nonessential (dispensable) amino acids which can be synthesized by the body 2) There are 9 essential (indispensable) amino acids that must be consumed in the diet B. Essential Amino Acids 1. Balanced diet can supply all amino acids needed to maintain health 2. Inadequate intake of essential amino acids will slow down (or even halt) production of new proteins. 3. Limiting amino acid: essential amino acid in shortest supply in the diet. 4. Needs for essential amino acids a. Infancy (40% of total protein intake) b. Childhood (20% of total protein intake) c. Adulthood (11% of total protein intake) C. Conditionally essential amino acids 1. Body requires more of a nonessential amino acid than it can make and thus becomes conditionally essential 2. Times of rapid growth, disease, or metabolic stress 3. Phenylketonuria (PKU): lack enzyme to convert phenylalanine to tyrosine, which makes tyrosine conditionally essential 6.2 Protein Synthesis and Organization A. Overview 1. Peptide bonds form between amino acids to form proteins (see Fig. 6-2) 2. Acids, enzymes, and other agents may break peptide bonds B. Protein synthesis 1. DNA code from nucleus directs synthesis of polypeptides in cytoplasm (see Fig. 6-3) a. Transcription: mRNA transfers DNA code from nucleus to cytoplasm b. Translation: in cytoplasm, mRNA travels to ribosomes where DNA code is translated into a protein (tRNA brings amino acids to the ribosome to form the protein) c. Protein synthesis requires energy 2. Twist and fold polypeptide to intended protein structure 3. Defects in genetic code cause defects in proteins C. Protein organization 1. Sequence of amino acids determines shape of protein 2. Unique 3-D shape of proteins directs function 3. Sickle cell disease (defective hemoglobin) is an example of genetic disease caused by sequence of amino acids that are out of order (see Fig. 6-5) D. Denaturation of proteins 1. Alters structure and function of protein by uncoiling the protein (see Fig. 6-11) 2. Can be caused by acid, base, heat, agitation 3. Often destroys normal physiological functions 4. Useful for some body processes (e.g., digestion) 6.3 Protein in Foods A. Overview 1. 70% of protein we consume is from animal sources (see Fig. 6-6) although consumption is declining for U.S. consumption of meat and poultry 2. Figure 6-6 presents sources of protein from MyPlate B. Protein Quality of Foods 1. High-quality (complete) proteins a. Provide all essential amino acids b. Support body growth and maintenance c. Animal proteins (except gelatin) 2. Lower-quality (incomplete) proteins a. Lack one or more amino acids b. Plant proteins (except soy protein) c. Limiting amino acids 3. Complementary proteins a. Two or more incomplete proteins may be combined to make a complete protein (see Fig. 6-8) b. Complementing is important throughout the course of a day (not at one meal) c. If not complemented, incomplete proteins are used for energy needs or converted to carbohydrate or fat d. Plant protein sources deserve attention—contribute fewer calories, magnesium, fiber, and other nutritional benefits (see Fig. 6-9) C. A Closer Look at Plant Sources of Proteins 1. Beyond protein, plant sources supply: a. Magnesium b. Fiber c. Folate d. Vitamin E e. Iron f. Zinc g. Calcium h. Phytochemicals 2. Examples of plant protein sources a. Nuts: hard shell surrounds edible kernel, grows on a tree b. Seeds: grow on vegetable or flowering plants c. Legumes: plants with pods that contain a single row of seeds 1) Peas, beans, lentils, peanuts 2) Fermentation of indigestible carbohydrates found in some legumes may lead to intestinal gas, but actually promotes intestinal health D. Food Protein Allergies 1. Immune system mistakes food protein for foreign invader. 2. Common food allergies (see Fig. 6-10): Peanut/tree nuts, milk products, soy, wheat, eggs, fish/shellfish. 3. Food allergies occur in 8% of children 4 yo and older and 2% of adults. 6.4 Protein Digestion and Absorption A. Overview 1. Cooking food denatures proteins and softens tough connective tissue (see Fig. 6-11). 2. Cooking makes protein-rich foods easier to chew and swallow. 3. Cooking makes meats, eggs, fish, poultry safer to eat. B. Digestion 1. Begins in the stomach by enzymes (see Fig. 6-12) a. Proteins are denatured by stomach acid b. Pepsin breaks polypeptides into shorter peptides c. Gastrin: hormone that stimulates the release of stomach acid and pepsin; released in response to thinking about or chewing foods d. Pepsin is activated by stomach acid 2. In small intestine, digestive enzymes degrade proteins into shorter amino acid chains a. Cholecystokinin (CCK): hormone released from small intestine in response to presence of chyme; stimulates release of enzymes from pancreas b. Trypsin: enzyme from pancreas that digests protein in small intestine c. Enzymes on intestinal wall digest peptides to short chains of amino acids for absorption C. Absorption 1. Short amino acid chains are absorbed by active transport into cells lining small intestine. 2. Final digestion of amino acid chains into amino acids occurs in absorptive cells of the small intestine. 3. Amino acids travel to the liver via the portal vein. a. Combined into protein b. Converted to nonessential amino acids c. Broken down for energy needs d. Converted to glucose e. Converted to fat f. Released into bloodstream 4. In infants up to 4–5 months of age, GI tract is somewhat permeable to intact proteins—may predispose infant to food allergies (i.e., cow's milk and egg whites). 6.5 Putting Proteins to Work in the Body A. Overview 1. Adequate carbohydrate and fat must be consumed for efficient use of proteins in metabolism and formation of body structures 2. If calorie intake is inadequate to meet energy needs, proteins are utilized as an energy source B. Producing Vital Body Structures 1. Every cell contains protein and an amino acid pool used to form those proteins. 2. Excess protein intake does not increase protein synthesis 3. Inadequate protein intake can prevent protein synthesis 4. Proteins are in a state of constant protein turnover a. e.g., Intestinal tract cells b. Protein turnover: cells respond to changing environment by producing proteins that are needed and disassembling proteins that are not needed c. Processes of rebuilding and repairing body proteins slows down with prolonged protein inadequacy 1) Muscles, blood proteins, and vital organs decrease in size 2) Brain resists breakdown C. Maintaining Fluid Balance (see Fig. 6-13) 1. Blood proteins help maintain body fluid balance. 2. Blood fluid can flow out of arteries to capillaries and extracellular space to provide nutrients. 3. Proteins cannot move into tissues and remain in capillary beds. 4. Proteins exert pressure—attracts fluids back into the blood. 5. Protein concentration in blood decreases in protein deficiency. a. Fluid shifts into tissues—edema b. Not enough proteins in blood to attract enough water back into blood D. Contributing to Acid-Base Balance 1. Assists in keeping blood slightly alkaline 2. Act as buffers—maintain pH within a narrow range E. Forming Hormones and Enzymes 1. Hormones: internal body messengers with important regulatory functions 2. Enzymes: speed chemical reactions that are crucial to cell function F. Contributing to Immune Function 1. Antibodies are important proteins 2. Malnutrition diminishes immune function G. Forming Glucose 1. If inadequate glucose is available to supply brain, red blood cells, and nervous tissue, amino acids will be converted into glucose (see Fig. 6-14). 2. Minor conversion of amino acids to glucose is normal (i.e., longer intervals between meals), but with starvation, muscle wasting and edema result from breakdown of protein for energy. H. Providing Energy 1. Proteins are not a major source of energy for weight stable person 2. Uses of protein for energy include: a. Prolonged exercise b. Calorie restriction 3. Ammonia (NH3) is waste product of metabolism of protein for energy 4. NH3 converted to urea and excreted in urine 5. Under most circumstances, cells use primarily fats and carbohydrate to meet energy needs because it is inefficient (wastes calories) to metabolize amino acids for energy. I. Contributing to Satiety 1. Proteins provide highest feeling of satisfaction after eating. 2. May contribute to calorie control during weight loss 6.6 Protein Needs A. Sufficient amount needed to balance output with intake B. Requirements determined by protein balance (see Fig. 6-15) 1. Protein equilibrium: intake compensates for losses 2. Positive protein balance a. Required to build new tissues (i.e., required for growth, or recovery from illness or injury) b. Protein intake > losses c. Insulin, growth hormone, and testosterone stimulate positive protein balance d. Resistance exercise enhances positive protein balance 3. Negative protein balance a. Protein intake < losses b. Occurs when acute illness reduces intake or in state of malnutrition C. Estimated requirements 1. Adults: 0.8 grams per kilogram body weight (based on healthy weight) 2. Increased needs during periods of growth (e.g., infancy and pregnancy) 3. Some experts suggest that endurance athletes and body builders may require as much as 1.7 grams per kilogram body weight 4. Acceptable range of protein intake: 10%–35% of total kilocalories 6.7 Does Eating a High-Protein Diet Harm You? A. Overview 1. Diets high in animal sources of protein may be simultaneously low in plant foods, which limits intake of fiber, some vitamins and minerals, and phytochemicals. 2. Excess animal sources of protein may contribute to excess saturated fat and cholesterol intake. 3. Some studies indicate that high-protein diets may increase calcium losses in urine, which is especially important for those with marginal calcium intake. 4. Excessive intake of red meat (especially processed forms) has been associated with increased risk of colon cancer. 5. Excess protein intake may place high burden on kidneys and/or contribute to formation of kidney stones and increase risk for dehydration B. Amino Acid Supplements 1. Consumed in hopes to build muscles or lose weight 2. Abundance of amino acids can overwhelm absorptive mechanisms of small intestine, triggering amino acid imbalances 3. Potential for toxicities of individual amino acids 6.8 Protein-Calorie Malnutrition A. Overview 1. Protein deficiency is rarely an isolated condition; likely accompanied by deficiencies of calories and other nutrients 2. Causes in developed countries a. Alcoholism b. Illness or injury (increased needs coupled with inadequate intake) 3. Diets low in calories and protein is cause in developing areas. 4. Effects in developing countries a. Stunted growth and development b. Increased susceptibility to disease B. Kwashiorkor (see Fig. 6-16) 1. Primarily protein deficiency 2. Associated with weaning from breast to starchy diet 3. Energy needs marginally met and protein intake inadequate 4. Symptoms a. Apathy, listlessness b. Failure to grow and gain weight c. Increased susceptibility to infection d. Reduced muscle mass e. Abdomen and leg edema (hallmark) f. Changes in hair color, flaky skin 5. Disease process can reverse with adequate diet C. Marasmus (see Fig. 6-16) 1. Primarily from insufficient amount of protein, energy, and other nutrients 2. No breastfeeding or weaned too early 3. Seen in cities where fashionable to bottle-feed, poor sanitation 4. Symptoms a. "Skin and bones" appearance b. Little or no subcutaneous fat 5. Full recovery from the disease may never occur if child does not receive large amount of calories and protein to recover 6. Brain may not grow to its full adult size Nutrition and Your Health: Vegetarian and Plant-Based Diets A. Overview 1. 4–5% U.S. adults are self-proclaimed vegetarians. 2. Vegetarianism is popular among teens and college students. 3. It is possible for well-planned vegetarian diets to meet nutritional needs. 4. Numerous health benefits include a. Decreased risk of cardiovascular disease and hypertension b. Decreased risk of diabetes c. Decreased risk of some forms of cancer d. Decreased risk of obesity e. Increased longevity 5. Other lifestyle factors (e.g., not smoking, not abusing alcohol, increased physical activity) may account for some of the health benefits of vegetarian lifestyles 6. 2010 Dietary Guidelines and MyPlate emphasize a plant-based diet consisting of whole grains, vegetables, and fruits 7. Current dietary guidance systems (e.g., Dietary Guidelines for Americans and AICR’s New American Plate) encourage emphasis on plant sources of protein B. Why Do People Become Vegetarians? 1. Ethics (i.e., killing animals) 2. Religion 3. Economics 4. Health (i.e., limit certain fats) 5. Environment C. Good for Disease Prevention 1. No cholesterol or trans fat 2. Little saturated fat 3. Health-promoting poly- and monounsaturated fats. 4. Soluble fiber binds cholesterol in small intestine. 5. Phytochemicals lower cholesterol, prevent blood clots, relax blood vessels. 6. AHA recommends inclusion of soy protein in heart healthy diet. 7. Good sources of nutrients implicated in heart health a. Vitamin E b. Folate c. Magnesium d. Copper 8. Vegan diet coupled with regular exercise and other lifestyle changes can reverse atherosclerosis 9. Cancer-fighting agents a. Phytochemicals acts as antioxidants b. Emphasis on breast, prostate, and colon cancers D. Increasing Plant Proteins in Your Diet 1. Try soy-based meat alternatives 2. Incorporate nuts and seeds into salads, baked goods, or use as snacks 3. Use beans instead of meats in mixed dishes 4. Use soy milk E. Food Planning for Vegetarians 1. Types of plant-based diets a. Fruitarian (not recommended): eat fruit, nuts, honey, vegetable oils b. Lactovegetarian: consume plant foods and dairy products c. Lactoovovegetarian: eat plant foods, dairy products, and eggs d. Vegan: only consume plant foods 2. Table 6-3 illustrates an example of vegetarian food plan based on MyPlate. F. Nutrients missing or minimal in plants include B-12 and calcium. G. Vegan Diet Planning 1. Complementing proteins to ensure adequate intake of essential amino acids (see Fig. 6-8) 2. Riboflavin sources include leafy greens, whole grains, yeast, and legumes 3. Vitamin D sources include fortified foods and regular sun exposure 4. Vitamin B-12 sources include fortified, ready-to-eat breakfast cereals and supplements 5. Iron sources include whole grains, dried fruits, nuts, and legumes; consume with vitamin C to enhance absorption; use iron cookware 6. Zinc sources include whole grains, nuts, and legumes; absorption is limited by phytic acid 7. Iodide sources include iodized salt 8. Calcium sources include fortified foods (e.g., orange juice, ready-to-eat breakfast cereals) 9. Omega-3 fatty acid sources include canola oil, soybean oil, seaweed, microalgae, flax seeds, and walnuts H. Special Concerns for Infants and Children 1. Picky eaters are already at risk for nutrient deficiencies 2. Nutrients of particular concern include iron, vitamin B-12, vitamin D, and calcium 3. High fiber content may limit calorie intake 4. Use complementary proteins and energy-dense foods BEST PRACTICES: TEACHING STRATEGIES, DEMONSTRATIONS, ACTIVITIES, ASSIGNMENTS, AND MORE 1. Have students complete the Rate Your Plate activity, "Protein and the Vegetarian". This activity will give students a chance to become familiar with dietary analysis software or food composition tables. 2. Have students plan a low cost, lactovegetarian menu that meets their particular RDA for protein. They could use the food-group plan for lacto-vegetarians and the exchange system as tools to do this. 3. From what students have learned about vegetarianism and plant protein sources, have them, as a class, plan two well-balanced vegetarian dinners that they would be willing to try. Make sure they vary the texture, temperature, color, and taste of each meal. This could be done during a class period, soliciting suggestions from the class and writing the suggestions on a transparency, board, poster paper, or similar medium. 4. Have students collect information on protein supplements that could be obtained from health food stores, sporting supply stores, or ordered from magazines for athletes and/or body builders. Have them work individually or in small groups to evaluate these products in relation to cost, protein quality and quantity, and presence of other nutrients. Develop a table comparing the quality of protein in supplements to dietary sources. 5. Have individual or small groups of students visit supermarkets, food co-ops, health food stores, or other food suppliers, and determine what plant sources of protein are available. Develop a table with food supplier, address, telephone number, sources of plant protein available, and approximate cost per unit. Have students develop and discuss ways in which these items could be incorporated in a meal; focus on complementation. This could include developing a recipe or combining various food items to make an appetizing, protein-complementary meal. You also could have students compare the price of one serving of animal protein and one serving of a plant protein. 6. Have students taste tofu, a quality plant protein. Tofu with different firmness can be cut into sampling pieces for the students to taste. Also present tofu in a tasty recipe such as a dip. Get their impressions of it. Ask the students to think of ways that tofu can be used in a vegetarian or omnivorous diet. 7. Have students visit the campus bookstore, a library, or area bookstore and locate five vegetarian resources including cookbooks. Have them reference each resource, noting the number of pages, whether it is soft cover or hard cover, and the price (if known). Compile a list of vegetarian resources for the students. 8. Have students visit an ethnic restaurant and order a meatless meal. During class ask them to report how they achieved complementary protein from the dishes they ordered. Instructor Manual for Wardlaw's Contemporary Nutrition Anne M. Smith , Angela L. Collene 9780078021374, 9781260092189
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