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Ch 4 ppt Presentation Transcript

  • 1. CHAPTER 4 LipidsEleanor D. Schlenker Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
  • 2. Health Issues and Lipids Health concerns related to dietary fat generally focus on two issues: 1. The high-energy intake associated with a diet high in fat 2. The negative health effects of saturated and trans fatty acids Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 2
  • 3. Health Issues and Lipids – Cont’dAmount of Fat Fat contains 9 kcal/g versus 4 kcal/g (protein and carbohydrates) High-fat intakes may supply excess kcalories, stored in adipose tissue Inappropriate increases in body fat are associated with type 2 diabetes, hypertension, and heart disease Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 3
  • 4. Health Issues and Lipids – Cont’dType of Fat High intakes of saturated fats and cholesterol promote atherosclerosis, the buildup of fatty deposits on the interior walls of the major arteries that increase risk of heart attack or stroke Saturated fat is found primarily in animal sources; cholesterol is found only in animal sources Unsaturated fats can decrease risk of cardiovascular disease Trans fats, produced in commercial processing of lipids, are deleterious to health Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 4
  • 5. Lipids in Nutrition and HealthFood Lipids Lipids found in food carry out important body functions  Provide fuel for energy • Food lipids yield 9 kcalories (kcal)/g  Supply essential fatty acids • Linoleic acid and alpha-linolenic acid Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 5
  • 6. Lipids in Nutrition and Health – Cont’dFood Lipids – cont’d Lipids found in food carry out important body functions – cont’d  Support absorption of the fat-soluble vitamins  Add to food palatability  Promote satiety Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 6
  • 7. Lipids in Nutrition and Health – Cont’dRoles in the Body Storage source of energy  Fatty acids are the preferred fuel of the heart muscle Thermal insulation to assist in temperature regulation Protection of vital organs from damage Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 7
  • 8. Lipids in Nutrition and Health – Cont’dRoles in the Body – cont’d Transmission of nerve impulses Form membrane structure Carrier of fat-soluble materials  Lipoproteins  Fat-soluble vitamins A,D, E, and K Precursors of other substances Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 8
  • 9. The Physical and Chemical Nature of LipidsPhysical Characteristics Lipid: Fats, oils, and related compounds that are insoluble in water and greasy to the touch Hidden fat: Foods that may appear to be mainly carbohydrates (bakery items) or protein (beef patty) often contain significant amounts of fat Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 9
  • 10. The Physical and Chemical Nature of Lipids – Cont’dChemical Characteristics Lipids are organic compounds consisting of a carbon chain as a “backbone,” with hydrogen and oxygen atoms and other radicals or groups of elements attached Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 10
  • 11. The Physical and Chemical Nature of Lipids – Cont’dChemical Characteristics – cont’d Carbohydrates and lipids have two important differences: 1. Lipids are more complex in structure, with more carbon (C) and hydrogen (H) atoms and fewer oxygen (O) atoms 2. The common structural units of lipids are fatty acids, whereas the common structural units of carbohydrates are simple sugars Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 11
  • 12. Characteristics of the Fatty Acids: Saturation Saturated lipids are hard, less saturated are soft, and unsaturated are liquid at room temperature Fatty acids that have some hydrogen spaces unfilled are less saturated Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 12
  • 13. Characteristics of the Fatty Acids: Saturation – Cont’dSaturated Fats Food lipids are composed of saturated fatty acids Examples: coconut oil, approximately 88% saturated; palm kernel oil, approximately 80% saturated Milk fats and meat fats are high in saturated fatty acids Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 13
  • 14. Characteristics of the Fatty Acids: Saturation – Cont’dMonounsaturated Food lipids made up of fatty acids with one hydrogen space unfilled, creating one double bond Examples: canola oil and olive oil Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 14
  • 15. Characteristics of the Fatty Acids: Saturation – Cont’dPolyunsaturated Fatty acids that have two or more spaces unfilled with hydrogen, creating two or more double bonds Examples: corn oil and safflower seed oil n-3 fatty acids in fatty fish are beneficial for cardiovascular health n-6 fatty acids, e.g., linoleic acid Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 15
  • 16. Characteristics of Fatty Acids: Chain Length Chain length ranges from 4 carbons to 22 carbons Chain length affects absorption  Long-chain fatty acids are more difficult to absorb and require a helping carrier  Short- and medium-chain fatty acids are soluble in water and can be absorbed directly into the bloodstream MCT oil may be used in intestinal diseases Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 16
  • 17. Essential Fatty Acids Two essential fatty acids for humans: 1. Linoleic acid (n-6) 2. Alpha-linolenic acid (n-3) Arachidonic acid, a fatty acid important in human nutrition, can be made from linoleic acid Eicosapentaenoic acid and docosahexaenoic acid can be made from alpha-linolenic acid Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 17
  • 18. Essential Fatty Acids – Cont’d Linoleic acid and alpha-linolenic acid have various roles in the body:  Skin integrity  Blood cholesterol regulation  Growth Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 18
  • 19. Essential Fatty Acids – Cont’d Linoleic acid and alpha-linolenic acid have various roles in the body – cont’d  Gene expression  Immune function  Blood platelet aggregation  Synthesis of hormone-like agents Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 19
  • 20. Dietary Reference Intakes Adequate Intake (AI) for linoleic acid (an n-6 fatty acid):  17 g/day for men ages 19 to 50 years  12 g/day for women ages 19 to 50 years  14 g/day for men age 51 and older  11 g/day for women age 51 and older Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 20
  • 21. Dietary Reference Intakes – Cont’d AI for alpha-linolenic acid (an n-3 fatty acid):  1.6 g/day for all adult men  1.1 g/day for all adult women Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 21
  • 22. Dietary Reference Intakes – Cont’d Special needs of infants  Arachidonic acid and docosahexaenoic acid play a critical role in infant development  Liberal amounts are found in breast milk  Commercial infant formula is now fortified with these fatty acids  Pregnant and lactating women are encouraged to eat 1-2 portions of fatty sea fish per week Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 22
  • 23. Food Sources Best source of linoleic and alpha-linolenic acids:  Vegetable oils Best sources of linoleic acid:  Corn oil, safflower oil, soybean oil, cottonseed oil, sunflower oil, and peanut oil Best sources of alpha-linoleic acid:  Canola oil, soy oil, linseed oil, rapeseed oil, and dark green leafy vegetables Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 23
  • 24. Food Sources – Cont’d Eicosapentaenoic and docosahexaenoic acids are obtained from fish  Can be made from alpha-linoleic acid Recommend two servings of fish per week  Vegans or others who do not eat fish may use fortified foods and fatty-acid-rich algae  High intakes may lead to excessive bleeding and interfere with other fatty acid metabolism  Foods are always the best sources Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 24
  • 25. Triglycerides Fatty acids are stored in the body in the form of triglycerides Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 25
  • 26. Triglycerides – Cont’d Triglycerides are made of three fatty acids attached to a glycerol base  Glycerides contain glycerol and fatty acids • Monoglyceride: glycerol is combined with one fatty acid • Diglyceride: with two fatty acids • Triglyceride: with three fatty acids Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 26
  • 27. Degree of Saturation Food lipids contain both saturated and unsaturated fats Foods from animal sources—such as meat, milk, and eggs—contain more saturated fats Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 27
  • 28. Degree of Saturation – Cont’d Most food lipids from plant sources, primarily vegetable oils, are unsaturated but there are exceptions:  Coconut oil and palm kernel oil are among the most saturated fats occurring naturally in foods Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 28
  • 29. Degree of Saturation – Cont’d The nutrition label can guide a consumers choice of fats  Indicates the number of grams of total fat, saturated fat, unsaturated fat, and trans fat per serving  Importance of considering serving sizes  Foods free of trans fats are not necessarily healthy Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 29
  • 30. Cis Versus Trans Fats Hydrogenation changes unsaturated liquid oils into solid fats such as margarine and shortening Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 30
  • 31. Cis Versus Trans Fats – Cont’d When oils are partially hydrogenated to produce more solid fats, the normal bend can change such that the two structural parts are on opposite sides of the bend  This form is called a trans fatty acid, meaning “opposite side” Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 31
  • 32. Cis Versus Trans Fats – Cont’d Trans fatty acids are found in breads, cakes, cookies, crackers, margarine, and frozen potato products Trans fatty acids decrease high-density lipoprotein (HDL) cholesterol levels and increase low-density lipoprotein (LDL) cholesterol levels Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 32
  • 33. Visible and Hidden Fat Visible Fat  Butter, margarine, vegetable oil, salad dressing, bacon, etc. Hidden Fat  Milk (except nonfat), egg yolk, cheese, nuts, seeds, olives, bakery items, frozen entrees  Meat and poultry contain visible and hidden fat Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 33
  • 34. Appropriate Intakes of Fat and Carbohydrates Acceptable Macronutrient Distribution Range (AMDR) for fat:  20% to 35% of total kcalories Keep saturated fat less than 10% of total calories Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 34
  • 35. Appropriate Intakes of Fat and Carbohydrates – Cont’d AMDR for carbohydrates:  45% to 65% of total kcalories Low carbohydrate diets may contain >45% of kcalories as fat Fat intakes below 10% of energy intake may not supply sufficient essential fatty acids Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 35
  • 36. Health Promotion Fast-food restaurants add to fat intake  On days with a fast-food meal, men and women obtain 34.9% and 34.6%, respectively, of their total kcalories from fat  On days when all meals are eaten at home or at food outlets other than the fast-food variety, fat supplies only 33.6% and 32.7% of total kcalories in men and women, respectively. Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 36
  • 37. Health Promotion – Cont’dLowering Fat Intake Substituting a modified-fat food for a higher- fat food Limiting portion sizes of higher-fat foods to reduce both fat and kcalories Choosing a food preparation method that limits or eliminates fat Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 37
  • 38. Fat Replacers Food technologists have developed fat replacers for use in processed foods In the United States, 79% of consumers buy foods containing fat replacers Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 38
  • 39. Fat Replacers – Cont’d Ingredients that can fulfill the functional role of fats in recipes but are lower in kcalories than fat Most are carbohydrates—plant polysaccharides, celluloses, or gums Most act as thickeners and emulsifiers Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 39
  • 40. Fat Replacers – Cont’d Olestra interferes with absorption of fat- soluble vitamins, so these are added to olestra-containing products Certain fat replacers are not digested and remain in the stomach longer; they may add to satiety and assist in appetite control Most (but not all) add fewer kcalories than would fat Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 40
  • 41. Lipid-Related CompoundsCholesterol Belongs to a family of substances called steroids and travels in the blood attached to long-chain fatty acids (as cholesterol esters) Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 41
  • 42. Lipid-Related Compounds – Cont’dCholesterol – cont’d Functions  Required for normal body function and can be synthesized in the liver  Precursor to steroid hormones  Formation of bile acids  Component of brain and nerve tissue  Component of cell membranes Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 42
  • 43. Cholesterol Cholesterol occurs naturally in animal foods but not plant foods Food sources containing cholesterol:  Egg yolk, meat, whole milk, and cheese  Liver and organ meats  Animal fats (but not plant fats) Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 43
  • 44. Cholesterol – Cont’dSuggested Cholesterol Intake The American Heart Association recommends that dietary cholesterol be held to 300 mg/day or less Intake averages about 358 mg in men and 237 mg in women Certain plant sterols interfere with absorption Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 44
  • 45. LipoproteinsFunction The liver serves as the bodys clearing house for fatty acids and cholesterol whether obtained from the diet or produced or released from body tissues Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 45
  • 46. Lipoproteins – Cont’dFunction – cont’d When received by the liver, fatty acids and cholesterol are:  Packaged into lipoproteins  Released into the circulation for transport to cells Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 46
  • 47. Lipid Transport Lipids are insoluble in water and therefore insoluble in water-based blood The body produces lipoproteins, packages of lipids wrapped in water-soluble protein Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 47
  • 48. Lipid Transport – Cont’d Phospholipids are molecules in which one of the three fatty acids attached to a glycerol base is replaced with a water-soluble phosphate (PO4-3) group Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 48
  • 49. Lipid Transport – Cont’d Phospholipids in cell membranes help lipid molecules move from the circulatory system into the cell The lipoproteins with their attached apolipoprotein serve as the major vehicle for lipid transport in the blood Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 49
  • 50. Classes of Lipoproteins Lipoproteins are classified according to their density Five lipoprotein classes are:  Chylomicrons  Very low-density lipoproteins (VLDLs)  Intermediate density lipoproteins (IDLs)  Low-density lipoproteins (LDLs)  High-density lipoproteins (HDLs) Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 50
  • 51. Cholesterol, Lipoproteins, and Cardiovascular Risk LDLs  Transport cholesterol from the liver to the tissues  Elevated LDLs promote atherosclerosis  Cause buildup of fatty plaque in blood vessels HDLs  Return cholesterol from the cells to the liver for excretion  Slow or prevent the progression of atherosclerosis and lower cardiovascular risk Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 51
  • 52. Digestion-Absorption-MetabolismDigestion Triglycerides are broken down into individual fatty acids for absorptionMouth No chemical breakdown of lipids Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 52
  • 53. Digestion-Absorption-Metabolism – Cont’dStomach Gastric lipase (tributyrinase) acts on emulsified butterfat General peristalsis continues the mechanical mixing of lipids with the stomach contents Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 53
  • 54. Digestion-Absorption-Metabolism – Cont’dSmall Intestine Digestive secretions for lipid breakdown come from three sources: 1. Bile from the liver and gallbladder: cholecystokinin (CCK) triggers its release 2. Enzymes from the pancreas: pancreatic lipase and cholesterol esterase 3. Enzyme from the small intestine: lecithinase Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 54
  • 55. Absorption Lipid absorption is complicated  Transporting lipids from the small intestine into the bloodstream takes place in three stages: • Stage I: Initial lipid absorption (micellar bile-lipid complex) • Stage II: Absorption within the intestinal wall (enteric lipase digestion and triglyceride synthesis) • Stage III: Final absorption and transport (chylomicrons and lipoprotein lipase) via the portal blood Copyright © 2011, 2007 by Mosby, Inc., an affiliate of Elsevier Inc. 55