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Lipids

Lipids. Triglycerides Fats and oils Phospholipids Lecithin Sterols Cholesterol. Objectives. After reading Chapter 4, class discussion and case study work, you will be able to Describe the role of lipids in the body Identify food sources of fats

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Lipids

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  1. Lipids Triglycerides Fats and oils Phospholipids Lecithin Sterols Cholesterol

  2. Objectives • After reading Chapter 4, class discussion and case study work, you will be able to • Describe the role of lipids in the body • Identify food sources of fats • Discuss lipid digestion, absorption and transport • Calculate calories from fat

  3. Objectives • Identify types (classification) of lipids • Discuss the health related effects of lipids • Blood lipid profile • Omega fatty acids • Trans fatty acids • Hydrogenation

  4. Triglycerides 4

  5. glycerol Triglycerides

  6. Triglycerides • glycerol + 3 fatty acids  triglyceride

  7. Fatty Acids Length of fatty acid 18-24 carbons in length Degree of Saturation Saturated fatty-acid Monounsaturated fatty-acid Polyunsaturated fatty-acid

  8. Fatty Acids • Point of unsaturation • Location of double bonds • Omega number • Omega-3 fatty acid • Omega-6 fatty acid

  9. Triglycerides • Degree of saturation determines: • Firmness • Stability • Oxidation • Antioxidants

  10. Rancidity • Definition: Deterioration of fat; resulting in undesirable flavor/odor • Flavor Reversion-soy oil; Cu, Fe • Hydrolytic: Separation of glycerol from fatty acids • Short chain fatty acids • Butyric fatty acid; butter • Oxidative: Loss of hydrogen in presence of air/heat • Oxidation of double bonds • Polyunsaturated fatty acids

  11. Trans Fats • Degree of unsaturation revisited • Hydrogenation • Cis vs. trans-fatty acids • Trans fat occurs naturally in meat and dairy foods • Conjugated linoleic in milk • Possibly positive for heart health

  12. p. 108 NRAEF

  13. Phospholipids

  14. Phospholipids • Phospholipids in foods-Lecithin • Roles of phospholipids • Plasma membrane • Emulsifiers

  15. Phospholipids

  16. Sterols • Found in plants and animals • Cholesterol is most abundant • Found in animals only • Found in every cell in man’s body • Body makes ~700mg/day • Dietary intake 200-400mg/day

  17. Dietary Cholesterol

  18. Sterols • Roles of sterols • Manufacture bile acids • Make hormones • Estrogen and testosterone • Make adrenal hormones • Make Vitamin D • Maintain cell membranes

  19. Fat Digestion • Hydrolysis • Triglycerides  monoglycerides, fatty acids, glycerol

  20. Fat Digestion • Mouth • Melting • Lingual Lipase • Stomach • Churning and mixing • Gastric Lipase

  21. Fat Digestion • Small intestine • Fat triggers the release of hormone • Cholecystokinin (CCK) • Gallbladder releases bile • Bile emulsifies fat so it can be more fully digested • Pancreatic lipase • Intestinal lipase

  22. Fat Digestion

  23. Enterohepatic circulation How bile travels through the body Fat Digestion

  24. Fat DigestionOverview

  25. p.152 5-17

  26. Lipid Transport • Lipoproteins • Chylomicrons • VLDL = very-low-density lipoproteins • LDL = low-density lipoproteins • HDL = high-density lipoproteins

  27. Lipid Transport

  28. Lipid Transport • Lipoproteins and health • LDL: carries cholesterol from liver to the cells of the body • High=Less healthy • HDL: carries cholesterol from the cells back to the liver • High=More healthy

  29. Roles of Triglycerides • Fat stores • Energy • Protection • Insulation • Provide essential fatty acids

  30. Essential Fatty Acids • Linoleic acid and the omega-6 family • Arachidonic acid • Linolenic acid and the omega-3 family • Alpha omega 3 fatty acids • Marine omega 3 fatty acid • EPA =eicosapentaenoic acid • DHA = docosahexaenoic acid

  31. Essential Fatty Acids

  32. Health Effects of Lipids • Blood lipid profile • Cholesterol=<200mg/dL • LDL=<100 • HDL=>60 • TG=<150 • Risks from saturated fats, trans fats, cholesterol • Benefits from polyunsaturated fats monosaturated, omega-3

  33. Health Effects of Lipids • Risks from trans fats • Alter blood cholesterol like saturated fats • Raise LDL cholesterol • Lower HDL cholesterol at high intakes • Increase inflammation & insulin resistance • AI = 5 gm/day • Risks from cholesterol • Not as implicated as saturated or trans fats • Beware cholesterol sensitivity • Limit intake <300 mg/day

  34. Health Effects of Lipids • Benefits from monounsaturated fats and polyunsaturated fats • Olive oil (monounsaturated) • Lowers LDL and total cholesterol • Lowers blood clotting factors • Lowers blood pressure • Provides phytochemicals which act as antioxidants

  35. Health Effects of Lipids • Benefits from omega-3 fats • Prevent arrhythmias • Lower blood pressure • Improve blood vessel function • May ease inflammation • Prevent repeat heart attack • 1 gm supplement daily for 3 years • Balance omega-6 and omega-3 intakes

  36. Recommended Intakes of Fat • DRI: 20-35% of energy intake • Cholesterol: 200-300 mg/day • Linoleic acid AI • 5% - 10% of energy intake • Linolenic acid AI • 0.6 - 1.2% of energy intake

  37. Guidelines to Groceries • Limit whole milk and milk products • Use vegetables, fruits, and grains • Avoid invisible fat • Avoid tropical oils • Use low fat meats and Alternatives

  38. Fat Distribution in Diet

  39. p. 162 Fig 5-23

  40. Beware the Label • “0 Trans Fat” – can still contain up to 0.5 grams • Look for “partially hydrogenated vegetable oil” or “vegetable shortening” • IOM recommends trans fat intake be “as low as possible”

  41. Fat Substitutes • “New” vegetable oils from “new” seed • Soybean & other seeds with very low levels of linolenic acid • More stable but less omega-3 fatty acid • Fat substitues • Z-Trim made from corn, soy, oat fiber • Oatrim made from whole oats • Fat replacers • Artificial fats • Olestra

  42. High-Fat Foods • Changing guidelines for fat intake

  43. High-Fat Foods • Cook with olive oil or canola oil • Monounsaturated fatty acids • Nibble on nuts • Omega-3 polyunsaturated fatty acids • Feast on fish • Marine omega-3 PUFA • But beware of mercury • Limit fatty meats, whole milk products, and tropical oils

  44. High-Fat Foods • Limit hydrogenated fat foods • Fried foods (fried in solid fats) • Fast foods (prepared in partially hydrogenated oils/fats • Commercial baked goods • Snack foods

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