1. Lipids

2. Properties of Lipids Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature Energy dense (9 kcal /gm)

3. Three Groups of Lipids Triglycerides: the main form of lipids in food and body (storage) Phospholipids Sterols

4. Triglyceride (TG) Structure Contain Carbons (C), Hydrogens (H), Oxygens (O) Glycerol + 3 fatty acids

5. Triglycerides (Ester bond) Glycerol + 3 FA’s Triglyceride + 3 H 2 0 H H--C--OH H--C--OH H--C--OH H O HO-C-R O HO-C-R O HO-C-R + H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H R + H2O R + H20

6. Triglycerides esterification desterfication H H--C--OH H--C--OH H--C--OH H Fatty Acid + H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H Fatty Acid

7. Phospholipid Built on a glycerol backbone Has at least one fatty acid replaced with phosphorus compound Found in body Synthesized by the body as needed

8. Phospholipid Structure

9. Functions of Phospholipids Make up cell membrane Emulsifier Bile acids Lecithins Improves food products

10. Emulsifier Hydrophilic end (attracts water) Hydrophobic end (attracts lipid)

11. Emulsification

12. Cholesterol Most common sterol A multi-ringed structure Does not have a glycerol backbone Waxy substance Do not readily dissolve in water Cholesterol is a sterol

13. Cholesterol Structure

14. Dietary Sources of Cholesterol Found in animal products only Never found in plants However ↑ saturated fat intake ↑ serum cholesterol

15. Serum (blood) Cholesterol Dietary cholesterol Endogenous cholesterol Made in liver Increases with increased SFA intake

16. Functions of Cholesterol Essential component of cell membrane Produced by the liver Found only in animal products Forms important hormones Estrogen, testosterone, vitamin D Precursor to bile acids

17. Fatty Acids Simplest form of lipids Common to most lipids, in the body and in foods Chain of 4-26 carbons bonded together, flanked by hydrogens Alpha end: is an acid Omega end: a methyl group Fats in foods are generally fatty acid mixtures

18. Differences in Fatty Acids Number of carbons Degree of saturation Number of single or double bonds in carbon chain Saturated Monounsaturated Polyunsaturated Point of first unsaturated bond Omega-3 Omega-6

19. Fatty Acid Structure omega endalpha end stearic acid (C18:0) H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

20. Saturated Fatty Acids (SFA) All the bonds between carbons are single connections and the carbons are filled with hydrogen Foods containing primarily saturated fats tend to be solid at room temperature Medium chain (coconut oil) and short- chain saturated fatty acids (dairy fat) may be liquid

21. Saturated Fatty Acids Don’t spoil easily, therefore longer shelf life High intakes of sfa are associated with an increased risk of cardiovascular disease

22. Sources of SFA Animal fats (meat, dairy) Tropical oils (coconut and palm oil) Hydrogenated fats

23. Saturated Fatty Acid Structure omega endalpha end degree of saturation: single carbon bond stearic acid: C18:0 H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

24. Monunsaturated Fatty Acids (MFA) One double bond between the carbons (missing hydrogens) Liquid at room temperature Easily oxidized → becomes rancid Double bonds are weak points Easily broken by oxygen (oxidized)

25. Monounsaturated Fatty Acids Canola, olive, peanut oil contain a high percentage of monounsaturated fatty acids MFA decreases CVD risk

26. Monounsaturated Fatty Acid Structure omega endalpha end One double bond ω-9 C18:1 H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

27. Polyunsaturated Fatty Acids (PUFA) More than one double bond between the carbons Liquid at room temperature Easily oxidized Polyunsaturated fat decreases CVD risk when substituted for SFA

28. Polyunsaturated Fatty Acids Corn, soybean, sunflower, and safflower oils are rich in polyunsaturated fatty acids (PUFA)

29. Polyunsaturated Fatty Acid Structure (Fig. 5-1-C) omega endalpha end > 2 double bonds H H H H H H H H H H H H H O H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

30. Fatty Acid Profiles in Foods

31. Hydrogenation of Fatty Acids Addition of H to C=C double bonds Breaks double bonds Formation of trans fatty acid (similar to shape of saturated fatty acid)

32. Hydrogenation of Fatty Acids Process used to solidify an oil Resistant to oxidation Increases shelf life Can be reused longer in frying However resulting trans fatty acids are associated with ↑ CVD risk

33. Cis and Trans Fatty Acid

34. Health Dangers of Trans Fatty Acids Raises LDL Lowers HDL Increases risk for heart disease Current intake is~3% of total kcals Soon to be on food labels

35. Sources of Trans Fatty Acid Stick margarine Shortening Crackers Hydrogenated fats Deep-fried foods High fat baked goods Non-dairy creamers

36. Rancidity Decomposed oils Breakdown of the C=C double bonds by ultraviolet rays, &/or O 2 Yields unpleasant odor and flavor PUFA more susceptible Limits shelf life

37. Prevention of Rancidity Hydrogenation Addition of vitamin E Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT)

38. Functions of Fats Provide essential fatty acids Provide energy (muscles and many organs burn fat) Supply fat soluble vitamins Satiety Texture and flavor

39. Essential Fatty Acids Body can only make double bonds after the 9th carbon from the omega end Needed for immune function, vision, cell membrane, and production of hormone-like compounds

40. Essential Fatty Acid- Omega-3 (alpha-linolenic acid) omega endalpha end 1st double bond is located on the 3rd carbon from the omega end H H H H H H H H H H H H H H H H H O H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H

41. Omega-3 Fatty Acid Primarily from fish oil Also found in canola or soybean oil Recommend intake of ~2 servings of fish per week

42. Essential Fatty Acid- Omega-6 (alpha-linoleic acid) omega endalpha end 1st double bond is located on the 6th carbon from the omega end H H H H H H H H H H H H H O H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

43. Omega-6 Fatty Acid Found in vegetable oils Only need ~ 1 tablespoon a day

44. Essential Fatty Acids Omega-3 Omega 6 Alpha-linolenic acid Linolenic acid DHA EPA Arachidonic Acid (docosahexanoic (eicosapentaenoic acid) acid)

45. Effects of Essential Fatty Acids Archidonic acid (Omega-6 ) increase blood clotting increase inflammatory responses DHA, EPA (Omega-3) decrease blood clotting reduces heart attack excess may cause hemorrhagic stroke large amounts may decrease inflammation pain with rheumatoid arthritis

46. Signs and Symptoms of Essential Fatty Acids Deficiency Flaky, itchy skin Diarrhea Infections Retarded growth and wound healing Anemia

47. Functions of Body Fat Energy store Adipose cells 1 pound fat = 3500 calories Insulation Subcutaneous fat Protection Internal organs

48. Lipids in Foods

49. Hidden Fat Look on the Nutrition Facts Look on the lists of ingredients Control portion size

50. Reduced Fat Foods Sugar is commonly added in place of fat Check calorie content

51. Fat Substitutes Water (diet margarine) Z-trim (starch derivative that binds with water) Fiber cellulose (Maltrin, Stellar, Oatrim) Dairy-Lo (protein globules) Olestra (links fatty acid to sucrose) not digested fat-soluble vitamins issue

52. Digestion of Fat in the Stomach Gastric lipase works only in an acidic environment Gastric lipase acts on triglycerides containing short & medium chain fatty acid Longer fatty acid chain is not affected by the stomach

53. Digestion of Fat in the Small Intestine Primary site of fat digestion CCK stimulates pancreas to release pancreatic lipase Pancreas release lipase Bile acid emulsifies digested fat Fat is broken down to monoglycerides and fatty acids

54. Absorption of Fat Diffuse into the absorptive cells Short and medium chain (<12 C) fatty acids are water soluble Enters the portal system Long chain fatty acids reforms into TG Enters the lymphatic system

55. Carrying Fat in the Bloodstream Water (blood) and oil (fat) are incompatible Unique system of fat transportation is needed Fat

56. Transportation of Digested Fat Re-formed into triglycerides Packaged into chylomicrons Lipoprotein lipase breaks down triglycerides in the chylomicrons Fatty acids are absorbed by cells Takes 2-10 hours to clear chylomicron

57. Lipoproteins

58. Transportation of Synthesized Fat Fat and cholesterol made primarily by the liver Very Low Density Lipoprotein (VLDL) Low Density Lipoprotein (LDL) Receptor pathway for cholesterol uptake Scavenger pathway for cholesterol uptake

59. Scavenger WBC removes (oxidized) LDL from circulation Prevents oxidized LDL from returning to circulation Build-up of plaque on walls of the blood vessels Leads to plaque and atherosclerosis Causes: smoking, diabetes, HTN, homocysteine, LDL Scavenger Pathway

60. Antioxidant Reduces oxidation Slows LDL uptake into scavenger cells Need for supplements of antioxidants?

61. High Density Lipoprotein (HDL) Synthesized by liver and intestine High proportion of protein Picks up cholesterol from dying cells and other sources Transfers cholesterol to other lipoproteins for transport to the liver for excretion HDL can also transfer directly back to the liver

62. Benefits of (a high) HDL (level) Remove cholesterol from the blood stream HDL may block oxidation of LDL Reduce risk of heart disease Pre-menopausal women have higher HDL

63. Functions of Lipids Provide energy Efficient storage of energy Insulation Protection Transport fat-soluble vitamins Satiety Flavor and mouth feel

64. Recommendation No RDA 4% of total kcal should come from essential fatty acids No more than 15% from PUFA Current diet supplies ~33% of total kcal from fat much from animal, whole milk, pastries, cheese, margarine, and mayo

65. Dietary Reference Intakes (2002 Update) 20-35% total calories from fat ≤30% with typical American diet Up to 35% with more monunsaturated fat

66. American Heart Association Population Guidelines ≤10% total calories from lipid-raising fats (saturated fat and trans fat) ≤10% total calories from polyunsaturated fat At least 10% of calories from monounsaturated fat <300 mg cholesterol/day Eat two servings of fish/week