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Lecture Outline Chapter 6 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fats and Other Lipids Chapter 6 Insert photo of fries and dip from chapter opener Chapter Learning Outcomes 1. Distinguish various lipids and identify at least one physiological role of each type of lipid. 2. Identify major food sources of lipids, including trans fatty acids. 3. Explain the process of atherosclerosis and list at least 6 risk factors of cardiovascular disease. 4. Distinguish HDL cholesterol from LDL cholesterol. 5. Identify major dietary sources of omega-3 fatty acids. 6. List dietary and other lifestyle actions that can reduce the risk of cardiovascular disease. Quiz Yourself True or False 1. To lose weight, use regular, stick margarine instead of butter because it has 25% fewer kilocalories per teaspoon. T F 2. Egg yolks are a rich source of cholesterol. T F 3. Taking too many fish oil supplements may be harmful to health. T F 4. On average, Americans consume 60% of their calories from fat. T F 5. Increasing your intake of trans fats can reduce your risk of heart disease. T F How Did You Do? 1. False Regular stick margarine has about the same kcal/teaspoon as butter. 2. True Egg yolks are a rich source of cholesterol. 3. True Taking too many fish oil supplements may be harmful to health. 4. False The average American consumes about 1/3 of his/her daily energy intake from fat. 5. False Increasing your intake of trans fats may increase your risk of heart disease. Understanding Lipids Lipids include: - Fatty acids - Triglycerides - Phospholipids - Cholesterol • Lipids are – insoluble in water – less dense than water “Oil and Water Don’t Mix” Since oil is less dense than water, it floats on top. • Insert bottle of oil and vinegar from page 145 Fatty Acids Fatty acids contain a hydrocarbon chain (carbon and hydrogen atoms) with a methyl group (CH3) at one end and an acid group (COOH) at the other. Insert Figure 6.1 Fatty acids vary in their number of carbons: Short chain fatty acids — 2 to 4 carbons Medium chain fatty acids — 6 to 12 carbons Long chain fatty acids –- 14 to 24 carbons Saturation Fatty acids also vary by saturation. • Saturated – each carbon atom within the chain holds 2 hydrogen atoms. • Unsaturated – one or more carbon atoms within the chain lack 2 hydrogen atoms, and as a result, the molecule has 1 or more double bonds. Insert figure 6.1 Unsaturated Fatty acids Insert figure 6.1 Essential Fatty Acids Insert figure 6.2 The 2 essential fatty acids are: 1) Alpha-linolenic acid 2) Linoleic acid Benefits of Essential Fatty Acids • Precursors of prostaglandins Hormone-like substances formed from EPA, DHA, and arachidonic acid • Effects of prostaglandins: – Stimulate uterine contractions – Regulate blood pressure – Promote immune system response Trans Fats What are trans fats? Unsaturated fats with at least 1 trans double bond rather than the more common cis bond Insert figure 6.3 a from page 148 Hydrogenation Hydrogenation: Process that adds hydrogen atoms to liquid vegetable oils Partial hydrogenation: – Not all double bonds are hydrogenated. – Natural cis double bonds convert to the unhealthy trans form. Trans Fats and Health • Used in many processed foods • High amounts of trans fats in diet increase heart disease risk by raising blood cholesterol levels. • FDA requires amount of trans fat displayed on Nutrition Facts panel. Triglycerides • Composed of 3 fatty acids attached to a glycerol “backbone” • ~ 95% of lipids in the body and foods is in the form of triglycerides. Insert figure 6.4 Approximate Percentages of Saturated and Unsaturated Fatty Acids in Common Fats and Oils Insert Table 6.1 Insert figure 6.5 Phospholipids Chemically similar to a triglyceride, except 1 fatty acid is replaced by a compound containing phosphorus and nitrogen groups Lecithin - The main phospholipid in foods such as egg yolks, liver, wheat germ, peanut butter, and soy Hydrophobic/ Hydrophilic Phospholipids act as emulsifiers, because they have hydrophobic and hydrophilic regions. • Hydrophobic region – Attracts lipids and avoids water • Hydrophilic region – Attracts water and avoids lipids Insert figure 6.5 Emulsification Insert Figure 6.6 Cholesterol Cholesterol: sterol containing carbon, hydrogen, and oxygen atoms arranged in a complex ring-like structure Insert figure 6.7 Functions of Cholesterol The body uses cholesterol to make various substances, including: – Vitamin D – Steroid hormones • Estrogen • Testosterone – Bile Cholesterol Content of Some Common Foods Insert Table 6.2 Digesting Triglycerides Insert figure 6.8 In the duodenum, pancreatic lipase digests triglycerides, forming primarily: - Monoglycerides - Free fatty acids Bile Bile — made in the liver and stored in the gallbladder – Bile contains bile salts. Emulsification occurs in the small intestine, as fat droplets are coated with bile salts. Insert Figure 6.9 Chylomicron Formation Insert figure 6.9 Journey Into General Circulation Insert figure 6.10 Overview of Lipid Digestion 1. Stomach — minor fat digestion occurs 2. Liver — produces bile that helps emulsify fat (bile is stored in gallbladder) 3. Pancreas — secretes lipase into small intestine 4. Small intestine — main site for lipid digestion and absorption 5. Anus — less than 5% of undigested fat is excreted in feces Insert figure 6.11 Recycling Bile Salts Enterohepatic Circulation Liver: uses cholesterol to make bile salts Gallbladder: stores bile before release into small intestine Small intestine: site where bile emulsifies fat. Portal vein: returns bile salts to liver, where the compounds are recycled Insert Figure 6.12 Using Triglycerides for Energy Adipose cell — stores a large triglyceride droplet Adipose cells can break down triglycerides into fatty acid and glycerol molecules, and release them into blood stream. Other cells remove fatty acids from circulation and use them for energy. Liver can convert glycerol to glucose— another energy source. Triglycerides provide 9 kcal/g (carbohydrate and protein provide 4 kcal/g) Insert Figure 6.13 Americans’ Lipid Consumption Patterns and Recommendations Average Annual Fat Intake 1909 – 1919 - 42 lbs/person 1990 – 1999 - 70 lbs/person Acceptable Macronutrient Distribution Range 20 to 35% of total calories U.S. Dietary Guidelines 2005 < 20 to 35% of total calories < 10% of calories from saturated fats < 300 mg cholesterol daily Avoid foods with trans fatty acids Understanding Nutritional Labeling: Lipids Lipid information required on Nutrition Facts panel: - Total kilocalories from fat - Total fat (g) - Saturated fat (g) - Trans fat (g) - Cholesterol (mg) Panel may include: - Polyunsaturated (g) - Monounsaturated (g) Insert Fig. 6.14 Why “Grams of Fat” May Not Add Up 2g Total Fat Saturated Fat Trans Fat Poly. Fat Mono. Fat ? 0g 0g 1g 0g 1 g* * If a food has < 0.5 g of a specific fat it can be labeled as having “0 g.” Insert Figure 6.14 Cardiovascular Disease (CVD) • Diseases of the heart and blood vessels – Heart disease (“coronary artery disease”) – Stroke • 1 in 3 adult Americans have some form of CVD. • In 2004, CVD was responsible for ~36% of deaths in the U.S. From Atherosclerosis to Cardiovascular Disease Atherosclerosis — disease in which lipid-containing plaques build up inside artery walls. Insert figure 6.15 Plaque forms in arteries when something irritates artery walls. • Plaque narrows arteries, interfering with circulation. • Plaque may also result in the formation of a fixed clot— a thrombus. Embolus Formation A thrombus that breaks away and travels through the blood is an embolus. • If an embolus lodges in the heart, it can cause a heart attack (myocardial infarction). • If an embolus lodges in the brain and deprives brain cells of oxygen and nutrients, a stroke can result. Arteriosclerosis and Hypertension Arteriosclerosis - Condition that results from atherosclerosis - Characterized by loss of arterial flexibility - Commonly referred to as “hardening of the arteries” - Contributes to hypertension Hypertension - Chronic condition characterized by abnormally high blood pressure levels - May cause hardened arteries to tear or burst Cardiovascular Disease: Major Risk Factors Insert Table 6.3 Modifiable Risk Factors Hypertension* Diabetes* Excess body fat* Elevated blood cholesterol (LDL)* Physical inactivity *Influenced by diet High-density Lipoproteins HDL commonly called “good” cholesterol • Transports cholesterol away from tissues and to the liver where it can be eliminated Insert Figure 6.18 Low-density Lipoproteins LDL commonly called “bad” cholesterol • Conveys cholesterol to tissues • May become oxidized LDL and contribute to atherosclerotic plaque Insert Figure 6.18 Roles of HDL, LDL, and Oxidized LDL Insert figure 6. 19 Very Low-density Lipoproteins High levels may contribute to atherosclerosis VLDL primarily carries triglycerides Insert Figure 6.18 Assessing Your Risk of Atherosclerosis Lipid Profile Blood test that determines total cholesterol, HDL and LDL cholesterol, and triglyceride levels Desirable levels: Total Cholesterol LDL Cholesterol HDL Cholesterol Triglycerides < 200 mg/dl < 100 mg/dl > 40 mg/dl < 150 mg/dl C-reactive Protein • High-sensitivity C-reactive protein (hs-CRP) - Protein produced primarily by liver in response to infection and inflammation - Marker for CVD and hypertension (“Marker” = early physiological warning sign that can be measured) Dietary Recommendations to Reduce Risk of CVD Limit: - saturated fats to <7% of kcal - trans fats to <1% of kcal - polyunsaturated fats to ~10% of kcal - total fat to 35% or less of total energy intake Choose unsaturated fats to replace saturated and trans fats. Include omega-3 rich fish twice a week. Dietary Recommendations to Reduce Risk of CVD (continued) Include fiber-rich foods, especially sources of soluble fiber. For people who consume alcohol, limit to 1-2 drinks/day. Rich Food Sources of Omega-3 Fatty Acids Insert Table 6.5 Ways to Lower Your Risk of CVD Insert Table 6.6 Genetic Factors Homocysteine - Amino acid associated with risk of CVD - Vitamin B-6 and folate are needed to metabolize homocysteine. - Some people have a genetic predisposition for high homocysteine levels. High-fat Diet and CVD - Scientists have identified gene that increases risk of CVD, particularly when people with the gene consume high-fat diets. Should You Avoid Eggs? • Eating an egg/day does not increase coronary artery disease or stroke risk. Is It Safe to Eat Butter? Common Questions About • “Stick” margarine may be more harmful to health,Fats because it contains cholesterol-raising trans fat. Liquid or soft margarines may be less harmful. Will Weight Loss and Exercise Help? • Achieving a healthy body weight often reduces CVD risk. Excess abdominal fat is associated with elevated LDL levels. Food Selection and Preparation Strategies to reduce dietary fat include: Reduce intake of fried foods. Purchase lean cuts of meat and trim visible fat. Replace some fatty foods with reduced-fat or fat-free alternatives. Replace high-fat sandwich meats with nut butters. Choose low-fat snack foods. Use less salad dressing on salads. Fat Replacers Synthetic fat replacers developed to meet consumer requests for lower fat foods Oatrim Simplesse Olestra What If Lifestyle Changes Don’t Work? People who cannot lower blood cholesterol levels after lifestyle modifications may need prescription drugs such as: Statins — class of medications that interfere with liver’s metabolism of cholesterol “Zetia©” — inhibits intestinal absorption of cholesterol Chapter 6 Highlight Drink to Your Health? Ethanol (“Alcohol”) • Simple 2-carbon compound • In beer, wine, vodka, whiskey, sake, koumiss, and kefir Insert Figure 6.A Alcohol Production Alcohol production requires: - Microbes (typically yeast) - Warm conditions - A source of simple sugar Typical sugar sources for common beverages are grains, fruits, and potatoes. Koumis is made from mare’s milk. Kefir is from camel’s milk. Approximate Alcohol, CHO, & Kcal Contents of Alcoholic Beverages Insert Table 6.A How the Body Processes Alcohol • Alcohol requires no digestion. – Rapidly absorbed in the mouth, esophagus, stomach, and small intestine • Detoxification begins in stomach where alcohol dehydrogenase metabolizes ~20% of alcohol consumed. – Most alcohol is absorbed in small intestine – Travels to the liver where it is metabolized Main Pathway for Alcohol Metabolism At relatively low doses, the enzymes alcohol dehydrogenase and acetaldehyde dehydrogenase convert alcohol to acetyl CoA. Acetyl CoA can be used to form glucose or fatty acids. Insert Figure 6.B 2nd Pathway for Alcohol Metabolism (Also occurs in the liver) At high doses, the liver’s ability to metabolize alcohol using the dehydrogenase pathway is overwhelmed. Under these conditions, the microsomal ethanol oxidizing system (MEOS) is used. - MEOS wastes energy as the heat produced dissipates into the environment. Factors That Influence Alcohol Metabolism Sex - Men have • • • more gastric alcohol dehydrogenase larger livers that can metabolize more alcohol at a time more body water As a result, a man’s BAC rises more slowly than a woman’s. Inset Figure 6.D Factors That Influence Alcohol Metabolism Prior Drinking History Regular drinkers develop tolerance – level of alcohol-detoxifying liver enzymes increase As tolerance increases, alcohol dependence (alcoholism) is likely to occur Classifying Drinkers Insert table 6.B Alcohol Abuse and Dependence Data on U.S. alcohol abuse: - Based on U.S.D.H.H.S. data, ~ 15 million Americans, over age 12 yrs, abused or were dependent on alcohol in 2003. - Alcohol abuse negatively affects 13% of Americans at some point in their lives. Alcohol Abuse vs Dependence Abuse Drinker: - has control over alcohol intake - does not have a powerful craving for alcohol - does not experience withdrawal symptoms Dependence Drinker: - has uncontrollable need to drink - is unable to limit alcohol consumption - suffers withdrawal symptoms - develops tolerance to alcohol Signs of Alcohol Abuse Insert Table 6.C Alcohol and Health Effects vary from person to person due to: - Differences in overall health - Drinking habits - Genetic backgrounds Alcohol affects every cell in the body and excesses can damage every organ system. Alcohol and the Body • Insert figure 6.D Alcohol and the Brain Effects on the CNS appear within a few minutes after consumption. Acts as a depressant, slowing transmission of messages between nerve cells. Effects on the brain vary and depend on blood alcohol concentration (BAC) . Typical Effects of Alcohol at Various BAC Levels Insert Table 6.D Alcohol and the Liver Excessive amounts of alcohol are converted to fatty acids in the liver. “Fatty liver” • condition is reversible if the person avoids alcohol. Continued alcohol consumption results in fat buildup in liver • destroys liver cells and results in scar tissue formation Liver cirrhosis — irreversible hardening of liver Alcohol and the Cardiovascular System and Cancer Cardiovascular system Excess consumption can damage heart muscle and elevate blood pressure. Cancer Chronic drinkers are more likely to develop cancers of oral cavity, esophagus, stomach, liver, pancreas, and colon/rectum. Alcohol and Drug Interactions • Prescription and over-the-counter medications may amplify effects of alcohol. • Alcohol may interact with certain drugs, causing serious side effects. Effects of Alcohol on Nutritional Status • Moderate alcohol stimulates appetite • Excessive alcohol: – inhibits appetite – displaces intake of nutrient-dense foods – interferes with body’s utilization of certain vitamins, minerals, and fat Alcohol and Body Water • Alcohol is not a “thirst quencher.” • It is a diuretic that suppresses the production of antidiuretic hormone (ADH). – As a result, kidneys excrete more urine, which is mostly water, and certain minerals and vitamins. Fetal Alcohol Syndrome • Alcohol is toxic to cells, including embryonic cells. • Infants born with fetal alcohol syndrome have physical deformities and experience developmental delays. Who Should Avoid Alcohol? Insert Table 6.E Health Benefits of Alcohol • Light to moderate alcohol intakes – Raise HDL cholesterol – Reduce blood levels of fibrinogen • Decrease platelet stickiness • Controversy over the health benefits of alcohol – Benefits of drinking red wine and beer rather than white wine and liquor • Alcohol itself or the antioxidants and certain vitamins in beer and red wines may provide health benefits. Alcohol and Physical Performance • American College of Sports Medicine recommends: – Athletes should learn about alcohol’s effects on health. – Avoid excessive alcohol during the 48 hrs before an event. – After exercise, avoid alcohol until body is rehydrated. Where to Get Help for Alcohol Abuse or Dependence • National Drug and Alcohol Treatment Referral Routing Service 1-800-662-HELP • Alcoholics Anonymous www.alcoholics-anonymous.org • National Clearinghouse for Alcohol and Drug Information ncadi.samhsa.gov • AlAnon/Alateen www.al-anon.alateen.org