Chapter 5

1. Chapter 5 Lipids, or Fats

2. Objectives • State functions of fats in body • Identify sources of dietary fats • Explain common classifications of fats • Describe disease conditions with which excessive use of fats are associated

3. Facts • Fats • Belong to group of organic compounds • Lipids • Greasy substances • Insoluble in water • Each gram of fat contains 9 calories • Composed of carbon, hydrogen, and oxygen • Lower proportion of oxygen than carbohydrates

4. Functions • Provide energy • Carry fat-soluble vitamins • Supply essential fatty acids • Protect and support organs and bones • Insulate from cold • Provide satiety after meals

5. Food Sources • Animal • Fatty meats and fish • Dairy products • Egg yolks (continues)

6. Food Sources • Plant • Cooking oils and margarine • Nuts • Avocados • Coconut • Cocoa butter

7. Visible and Invisible Fats • Visible • Fats in foods that are purchased and used as fats • E.g., butter, margarine, lard, cooking oils • Invisible • Fats not immediately noticeable • E.g., egg yolks, cheese, cream, salad dressings

8. Stop and Share • Consider the following scenario: • You are the nurse teaching a class about nutrition. A client asks about ways to decrease the amount of fat in his diet. What are some suggestions you can offer him? (continues)

9. Stop and Share • Beware of hidden fats • Decrease amount of fatty meats • E.g., bacon, sausage, luncheon meats • Use lean meats, instead • Use low-fat or skim milk • Use egg whites instead of yolks when possible • Egg white contains no fat • Almost entirely protein and water

10. Classification • Triglycerides • Most lipids in body • 95 percent • Composed of three fatty acids attached to framework of glycerol • Phospholipids • Sterols • Cholesterol

11. Fatty Acid Classification • May be classified by body’s need for them: • Essential fatty acids (EFAs) • Nonessential (continues)

12. Fatty Acid Classification • May be classified by degree of saturation with hydrogen atoms: • Saturated • Unsaturated • Monounsaturated • Polyunsaturated

13. Essential Fatty Acids • Cannot be synthesized by body • Must be obtained from diet • Two families: • Omega-3 • Omega-6

14. Nonessential Fatty Acids • Can be synthesized by body • Omega-9 fatty acids can be synthesized in body when EFAs present • Previously thought to be essential

15. Saturated Fats • Each of its carbon atoms carries all hydrogen atoms possible • In general, animal foods contain more saturated fatty acids than unsaturated • Usually solid at room temperature (continues)

16. Saturated Fats • E.g., meat, poultry, egg yolks, whole milk, whole milk cheeses, cream, ice cream, butter, chocolate, coconut, palm oil

17. Monounsaturated Fats • Have one place among carbon atoms where there are fewer hydrogen atoms attached than in saturated fats • Lower low-density lipoprotein (LDL or “bad” cholesterol) when they replace saturated fat in one’s diet (continues)

18. Monounsaturated Fats • E.g., olive oil, canola oil, avocados, cashew nuts • Recommend 15 percent of total daily calories

19. Polyunsaturated Fats • Have two or more places among carbon atoms where there are fewer hydrogen atoms attached than in saturated fats • E.g., cooking oils made from sunflower, safflower, sesame seeds, corn, or soybeans; soft margarines with liquid vegetable oil as major ingredient; fish (continues)

20. Polyunsaturated Fats • Foods containing high proportions of polyunsaturated fats • Usually soft or oily • Omega-3 • Lower risk of heart disease (continues)

21. Polyunsaturated Fats • Omega-6 • Lower cholesterol • Recommend 8 percent or less of total daily calories

22. Trans Fatty Acids (TFAs) • Produced when hydrogen atoms added to monounsaturated or polyunsaturated fats to produce semi-solid product • E.g., margarine, shortening • Raise LDL and total cholesterol (continues)

23. TFAs • Major sources: • Baked goods • Restaurant foods

24. Hydrogenated Fats • Polyunsaturated vegetable oils to which hydrogen has been added commercially to make them solid at room temperature • Hydrogenation • Process that turns polyunsaturated vegetable oils into saturated fats • E.g., margarine, shortening

25. Cholesterol • Sterol • Fatlike substance • Exists in animal foods and body cells • Does not exist in plant foods (continues)

26. Cholesterol • Essential for synthesis of bile, sex hormones, cortisone, and vitamin D • Needed by every cell in body, but manufactured by liver

27. Stop and Share • Consider the following scenario: • Your client has been diagnosed with a high cholesterol level greater than 200 mg per dL. Answer the following questions: • What risks are associated with a high cholesterol level? • What can be done to lower a high cholesterol level? (continues)

28. Stop and Share • High cholesterol leads to atherosclerosis • Cardiovascular disease in which plaque forms on inside of artery walls • Plaque • Fatty deposits containing cholesterol and other substances • Can lead to heart attacks and strokes (continues)

29. Stop and Share • Reduce amount of total fat, saturated fats, and cholesterol • Increase monounsaturated fats, lose weight, and exercise • Increase consumption of soluble dietary fiber (continues)

30. Stop and Share • Do not exceed daily cholesterol intake of 300 mg • In some cases, have medication prescribed

31. Digestion and Absorption • 95 percent of ingested fats digested • Chemical digestion of fats occurs mainly in small intestine • No digestion of fats occurs in mouth • Slight digestion in stomach where gastric lipase acts on emulsified fats (continues)

32. Digestion and Absorption • Digestion in small intestine • Bile emulsifies fats • Lipase reduces fats to fatty acids and glycerol • Absorption occurs through villi of small intestine

33. Lipoproteins • Bile joins with products of fat digestion to carry fat • Protein combines with final products of fat digestion to form lipoproteins • Lipoproteins carry fat in blood to body cells (continues)

34. Lipoproteins • Classified according to mobility and density • Types: • Chylomicrons • Very-low-density lipoproteins (VLDLs) • LDLs • High-density lipoproteins (HDLs)

35. Chylomicron • First lipoprotein identified after eating • Largest lipoprotein • Yet lightest in weight • Composed of 80 to 90 percent triglycerides

36. VLDLs • Made by liver to transport lipids throughout body • Composed of 55 to 65 percent triglycerides • Carry triglycerides and other lipids to all cells • As VLDL lose triglycerides, pick up cholesterol from other lipoproteins in blood • Become LDL

37. LDLs • Composed of 45 percent cholesterol with few triglycerides • Carry most of blood cholesterol from liver to cells • Level greater than 130 mg per dL • Considered to contribute to atherosclerosis • “Bad” cholesterol

38. HDLs • Carry cholesterol from cells to liver for eventual excretion • Level of 60 mg per dL or more • Considered to reduce risk of heart disease (continues)

39. HDLs • Increase by doing the following: • Exercising • Maintaining desirable weight • Giving up smoking • “Good” cholesterol

40. Metabolism and Elimination • Liver controls fat metabolism • In cells, fatty acids broken down to carbon dioxide and water • Releasing energy (continues)

41. Metabolism and Elimination • Excess fat stored as adipose tissue • Carbon dioxide and water removed from body by circulatory, respiratory, and excretory systems

42. Stop and Share • Consider the following scenario: • Your client asks you about a new dietary supplement that advertisers claim provides essential nutrients and lowers cholesterol “naturally.” How do you advise your client? (continues)

43. Stop and Share • Any new dietary supplement with nutritional claim should be evaluated carefully • If item not included in Recommended Daily Allowance (RDA) or DRI, assume medical research has not determined it essential • Ingestion of dietary supplements of unknown value could be damaging to one’s health

44. Phospholipid • Found in both plant and animal foods • Synthesized in liver • Natural emulsifier that helps transport fat in bloodstream • E.g., lecithin

45. Fat Alternatives • Olestra • Made from carbohydrates and fat • FDA approved for use in snack food • Food labels must indicate that it “inhibits absorption of some vitamins and other nutrients” • Should be used in moderation • Contains no calories • Can cause cramps and diarrhea (continues)

46. Fat Alternatives • Simplesse • Made from egg white or milk protein • Can be used only in cold foods • Not available for home use (continues)

47. Fat Alternatives • Oatrim • Carbohydrate-based • Derived from oat fiber • Can be used in baking • But not frying • Provides calories • But less than fat

48. Dietary Requirements • Deficiency symptoms occur when fats provide less than 10 percent of total daily calories • Food and Nutrition Board’s Committee on Diet and Health recommends that people reduce fat intake to 30 percent of total calories (continues)

49. Dietary Requirements • American Heart Association’s newest recommendation: • Consume ≤ 7 percent of saturated fats, 8 percent polyunsaturated fats, and 15 percent monounsaturated fats • At present, 36 percent of calories in U.S. diets derived from fats

50. Conclusion • Fats provide energy, carry essential fatty acids and fat-soluble vitamins, protect organs and bones, insulate from cold, and provide satiety after meals • Fats are composed of carbon, hydrogen, and oxygen • Found in both animal and plant foods (continues)