Chapter 4

1. Chapter 4 The Lipids: Fats and Oils © 2007 Thomson - Wadsworth

2. Requirements of the proposal . First you should establish a context for your research and demonstrate the need for it • Talk about how your study will meet this need, you may want to talk about the method(s) you will use • Your proposal should have the following elements:Introduction • Nature of the problem • Why the issue/problem is important • How your research would contribute to the solution of the problem Research question or hypothesisFor example, what is the relationship between two or more concepts, variables, phenomena, events, etc.Brief review of the relevant literature/bibliographyThis part contains a statement that explains why these studies or theories are important for your research, and where your research fits in relation to the literature (maximum of half a page).A description of the procedureThis can include: • A description of the theoretical or conceptual framework • Sources of evidence • Research design and method • Analytical techniques • A timetable for conducting and completing the study © 2007 Thomson - Wadsworth

3. Advice on Getting Started • The first step is to prepare a rough draft. Start by writing preliminary answers to the following questions: • What is the tentative title? (The title may change as your research progresses) • Why do you want to do this research? (What do you think you will be able to say when your research is complete?) • What steps will you have to take to accomplish what you want to do? Can you put those steps into sequential order? • What resources will you need to conduct the study? • What assistance from other people will you need? eg skills of a supervisor, other staff members. • Will Ethics Approval be required? © 2007 Thomson - Wadsworth

4. Ask Yourself 1. The body can store fat in virtually unlimited amounts. 2. Dietary cholesterol is found only in animal foods. 3. A person’s blood level of cholesterol is a predictor of that person’s risk of having a heart attack. 4. For the health of your heart, the fat you should avoid eating, most of all, is cholesterol. 5. The more monounsaturated fats you consume, the better it is for your health. © 2007 Thomson - Wadsworth

5. Ask Yourself 6. Fruits are essentially fat-free. 7. In general, the softest margarines are the most polyunsaturated. 8. Polyunsaturated fat has the same number of calories as saturated fat. 9. All foods that you eat should contain less than 10% of calories from saturated fat. 10. No one is free of atherosclerosis. © 2007 Thomson - Wadsworth

6. A Primer on Fats • Lipids: a family of compounds that includes: • Triglycerides (fats and oils) • Phospholipids (lecithin) • Sterols (cholesterol) • Obvious sources of fat are oil, butter, margarine and shortening. • Other foods contributing fat include meat, nuts, mayonnaise, salad dressings, eggs, bacon, gravy, cheese, ice cream and whole milk. © 2007 Thomson - Wadsworth

7. A Primer on Fats • Triglycerides (try-GLISS-er-ides): the major class of dietary lipids, including fats and oils. • Phospholipid (FOSS-foh-LIP-ids): a lipid similar to a triglyceride but containing phosphorus; one of the three main classes of lipids. • Sterols (STEER-alls): lipids with a structure similar to that of cholesterol; one of the three main classes of lipids. • Cholesterol (koh-LESS-ter-all): one of the sterols, manufactured in the body for a variety of purposes. © 2007 Thomson - Wadsworth

8. A Primer on Fats • Fats: lipids that are solid at room temperature. • Oils: lipids that are liquid at normal room temperature. © 2007 Thomson - Wadsworth

9. A Primer on Fats • After eating, the body stores some fat as an energy reserve. • The body has unlimited potential to store fat. • Excess carbohydrate and protein can be converted to fat, but they cannot be made from fat. • One pound of body fat is worth 3,500 calories. © 2007 Thomson - Wadsworth

10. A Primer on Fats • Satiety: the feeling of fullness or satisfaction that people feel after meals. • Fats slow the rate at which the stomach empties. © 2007 Thomson - Wadsworth

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12. Lipid Metabolism • Lipids are transported through 4 different forms of lipoproteins: • Chylomicrons: transport triglycerides from intestinal epithelial cells to lacteals (special lymph capillaries in villi). Once in circulation they travel to adipose tissue where triglycerides are stored. (2% protein) • VLDLs: carry triglycerides synthesized in the liver to adipose tissue. They are converted to LDLs. (10% protein) • LDLs: transport cholesterol to body cells via blood circulation. They are also called “bad cholesterol” because in high amounts they may deposit cholesterol around blood vessels. (25% protein) • HDLs: they remove excess cholesterol from cells and send to the liver for elimination. “Good cholesterol” (40% protein) © 2007 Thomson - Wadsworth

13. A Closer View of Fats • A triglyceride is made up of three units known as fatty acids and one unit called glycerol. • Fatty acids: basic units of fat composed of chains of carbon atoms with an acid group at one end and hydrogen atoms attached all along their length. • Glycerol (GLISS-er-all): an organic compound that serves as the backbone for triglycerides. About 95 percent of the lipids in foods and in the human body are triglycerides. © 2007 Thomson - Wadsworth

14. Phospholipids Hydrophilic head Hydrophobic tail © 2007 Thomson - Wadsworth

15. A Closer View of Fats • Fatty Acids differ in chain length or the number of carbons in a fatty acid. • Chain length affects solubility. • Fatty acids can be: • Short-chain • Medium-chain • Long-chain © 2007 Thomson - Wadsworth

16. A Closer View of Fats • Fatty Acids differ in the degree of saturation. • Saturation refers to the chemical structure—specifically to the number of hydrogens the fatty acid chain holds. • Saturated Fatty Acids are filled to capacity with hydrogen. • Unsaturated Fatty Acids hold an “empty spot” or point of unsaturation. © 2007 Thomson - Wadsworth

17. The Types of Fatty Acids • Saturated fatty acid: a fatty acid carrying the maximum possible number of hydrogen atoms (having no points of unsaturation). Saturated fats are found in animal foods like meat, poultry, and full-fat dairy products, and in tropical oils such as palm and coconut. © 2007 Thomson - Wadsworth

18. The Types of Fatty Acids • Unsaturated fatty acid: a fatty acid with one or more points of unsaturation. Unsaturated fats are found in foods from both plant and animal sources. Unsaturated fatty acids are further divided into monounsaturated fatty acids and polyunsaturated fatty acids. • Monounsaturated fatty acid: a fatty acid containing one point of unsaturation, found mostly in vegetable oils such as olive, canola, and peanut. © 2007 Thomson - Wadsworth

19. The Types of Fatty Acids • Polyunsaturated fatty acid: (sometimes abbreviated PUFA) a fatty acid in which two or more points of unsaturation occur, found in nuts and vegetable oils such as safflower, sunflower, and soybean, and in fatty fish. © 2007 Thomson - Wadsworth

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21. The Types of Fatty Acids • Essential fatty acid: a fatty acid that cannot be synthesized in the body in amounts sufficient to meet physiological need. • Linoleic (lin-oh-LAY-ic) acid, linolenic (lin-oh-LEN-ic)acid: polyunsaturated fatty acids, essential for human beings. © 2007 Thomson - Wadsworth

22. The Types of Fatty Acids • Omega-3 fatty acids, found in fish oils, offer a protective effect on health. • Interest in fish oils was first kindled when someone thought to ask why the Eskimos of Greenland, who eat a diet very high in fat, have such a low rate of heart disease. • Blood clot formation, inflammation (e.g. arthritis, asthma), irregular heart rhythm and cancer also seem to be beneficially affected by DHA and/ or EPA. © 2007 Thomson - Wadsworth

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24. Characteristics of Fats in Foods © 2007 Thomson - Wadsworth

25. Fatty Acids in Dietary Fats & Oils © 2007 Thomson - Wadsworth

26. Characteristics of Fats in Foods • Unsaturated fats are more likely to react with oxygen and become rancid. • Food manufacturers may alter fats and oils by: • hydrogenation (high-droh-gen-AY-shun): the process of adding hydrogen to unsaturated fat to make it more solid and more resistant to chemical change. • antioxidant (anti-OX-ih-dant): a compound that protects other compounds from oxygen by itself reacting with oxygen. • Emulsifier: a substance that mixes with both fat and water and can break fat globules into small droplets, thereby suspending fat in water. © 2007 Thomson - Wadsworth

27. The Other Members of the Lipid Family Phospholipids… • Important components of cell membranes. • Can serve as emulsifiers in the body, joining with both water and fat. • Also used in foods such as margarine, chocolate, salad dressings, and frozen desserts to keep the fats dispersed. • Widespread in foods. © 2007 Thomson - Wadsworth

28. The Other Members of the Lipid Family Sterols such as cholesterol… • Incorporated as an integral part of the structure of cell membranes. • Used to make bile for digestion. • Used to make sex hormones (estrogen and testosterone). • Made into vitamin D • Deposited in the artery walls, leading to plaque buildup and heart disease. Sterols such as cholesterol have a multiple-ring structure. © 2007 Thomson - Wadsworth

29. Five foods contribute up to 70% of the cholesterol in the US diet: Eggs (30%), Beef (16%), Poultry (12%), Cheese (6%) and milk (5%). © 2007 Thomson - Wadsworth

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31. How the Body Handles Fat • Bile: a mixture of compounds, including cholesterol, made by the liver, stored in the gallbladder, and secreted into the small intestine. Bile emulsifies lipids to ready them for enzymatic digestion and helps transport them into the intestinal wall cells. © 2007 Thomson - Wadsworth

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33. How the Body Handles Fat • The products of fat digestion are fatty acids, glycerol and monoglycerides. • Monoglyceride (mon-oh-GLISS-er-ide): a glycerol molecule with one fatty acid attached to it. A diglyceride is a glycerol molecule with two fatty acids attached to it. • The shortest fatty acids and glycerol pass by simple diffusion into the absorptive cells and without further processing can enter the blood stream, travel to the liver and be converted and used by the body. © 2007 Thomson - Wadsworth

34. How the Body Handles Fat • Long-chain fatty acids, phospholipids and cholesterol are insoluble in water and cannot be accepted by the body’s blood and lymph system. • Lymph (LIMF): the body fluid that transports the products of fat digestion toward the heart and eventually drains back into the bloodstream. • Lymph consists of the same components as blood with the exception of red blood cells. • These fats must be packaged into one of four types of lipoproteins for transport. © 2007 Thomson - Wadsworth

35. How the Body Handles Fat • Lipoproteins (LIP-oh-PRO-teens): clusters of lipids associated with protein that serve as transport vehicles for lipids in blood and lymph. The four main types of lipoproteins are: • Chylomicron (KIGH-loh-MY-cron): a type of lipoprotein that transports newly digested fat—mostly triglyceride—from the intestine through lymph and blood. • VLDL (very-low-density lipoprotein): carries fats packaged or made by the liver to various tissues in the body. • LDL (low-density lipoprotein): carries cholesterol (much of it synthesized in the liver) to body cells. A high blood cholesterol level usually reflects high LDL. • HDL (high-density lipoprotein); carries cholesterol in the blood back to the liver for recycling or disposal. © 2007 Thomson - Wadsworth

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39. “Good” vs. “Bad” Cholesterol • Oxidized LDL-cholesterol (o-LDL): the cholesterol in LDLs that is attacked by reactive oxygen molecules inside the walls of the arteries. • o-LDL is taken up by scavenger cells and deposited in plaque. • Foam cells: cells from the immune system containing scavenged oxidized LDL cholesterol that are thought to initiate arterial plaque formation. © 2007 Thomson - Wadsworth

40. “Good” vs. “Bad” Cholesterol • ATHEROSCLEROSIS: As LDL particles penetrate the walls of the arteries, they become oxidized-LDL and next are scavenged by the body’s white blood cells. • These foam cells are then deposited into the lining of the artery wall. • This process, known as atherosclerosis, causes plaque deposits to enlarge, artery walls to lose elasticity, and the passage through the artery to narrow. © 2007 Thomson - Wadsworth

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42. A normal artery provides open passage for blood to circulate. Plaques along an artery wall narrow the passage and obstruct blood flow. © 2007 Thomson - Wadsworth

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47. Eat Well Be Well: Nourish the Heart Heading • Become a savvy supermarket shopper. • Keep blood cholesterol at or below the recommended levels. • Balance energy intake with energy needs. © 2007 Thomson - Wadsworth

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