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Lipids

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Chapter 5:

Chapter 5 Fats Copyright © 2012, 2007 Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 1

LEARNING OBJECTIVES :

LEARNING OBJECTIVES 1. List physiologic and food functions of fats. 2. Identify the functions of essential fatty acids and describe the consequences of an essential fatty acid deficiency. 3. Describe the functions of phospholipids. 4. Differentiate among the structures of triglycerides, saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids and list foods that are good sources of saturated, monounsaturated, and polyunsaturated fatty acids. 5. Outline the functions of cholesterol and identify the sources of body cholesterol. 6. Outline the digestion, absorption, and metabolism of fat and lipids. 8. Define and discuss hydrogenation, emulsification, and trans fatty acids, and antioxidants. 9. Define lipoproteins and identify their role in digestion, absorption, and metabolism of fats. 11. Discuss the potential health consequences of overconsumption and underconsumption of fat. 2

Food Functions: Triglycerides:

Food Functions: Triglycerides Source of energy Palatability Satiety and satiation Nutrient source Contain or transport fat-soluble vitamins A, D, E, K Contain or transport essential fatty acids (EFA) Polyunsaturated fatty acids Skin lesions(eczema) 3

Physiologic Functions: Triglycerides :

Physiologic Functions: Triglycerides Stored energy Adipose tissue storage form of fat (mainly triglycerides) Important source of fuel during illness and food restriction, and major energy source for muscle work Organ protection Temperature regulator Insulation 4

Structure and Sources of Lipids Fats: Saturated and Unsaturated:

Structure and Sources of Lipids Fats: Saturated and Unsaturated Fats are one type of lipid Lipids class of organic molecules that are insoluble in water Three types of lipids are found in foods Triglycerides, phospholipids, sterols Triglycerides-Largest class of lipids in body and foods Composed of glycerol and three fatty acids Fatty acids: Saturated fatty acids Monounsaturated fatty acids Polyunsaturated fatty acids 5

Triglycerides:

Triglycerides Saturated fatty acid-solid at room tempt Lard, butter, coconut oil, meats Monounsaturated fatty acid Primary sources include olive oil, peanuts (peanuts and peanut oil), avocado, and canola oil Polyunsaturated fatty acid (PUFA) Sources: vegetable oils (corn, safflower, wheat germ, canola, sesame, and sunflower), fish, and margarine Omega-3 fatty acids ( linolenic acid) fish and fish oils Omega-6 fatty acids (linoleic acid) vegetable and nut oils Food sources of omega-3 fatty acids and supplements 6

Structure and Sources of Lipids Phospholipids:

Structure and Sources of Lipids Phospholipids Composed of Glycerol and 2 fatty acids, phosphate Soluble in water Body manufactures phospholipids, therefore not essential nutrient Lecithin, main body phospholipid, functions as emulsifier 7

Structure and Sources of Lipids Sterols:

Structure and Sources of Lipids Sterols Sterol structures are carbon rings interconnected with side chains of carbon, hydrogen, and oxygen Synthesized by body, therefore not essential nutrient Essential components of cell membrane and hormones Cholesterol most familiar sterol Dietary cholesterol 25% of body cholesterol; rest provided by liver synthesis Only animal-derived foods contain cholesterol 8

Fats as a Nutrient in the Body Digestion:

Fats as a Nutrient in the Body Digestion Mouth Primary fat digestive process is mechanical as teeth masticate fatty food Stomach Mechanical digestion continues through peristalsis Fat-splitting enzymes such as gastric lipase hydrolyze fatty acids from triglycerides 9

Digestion, cont’d:

Digestion, cont’d Small intestine Duodenum releases hormone cholecystokinin (CCK) CCK action causes gallbladder to release bile into small intestine Muscular action Pancreatic enzyme, lipase, breaks down triglycerides Some fats may pass through undigested; excreted 10

Absorption:

Absorption Bile salts assist movement of lipids to villi Triglycerides form into chylomicrons, transported through lymphatic system to circulatory system Muscle and adipose cells use fatty acids for energy or re-form into triglycerides that are stored as energy 11

Metabolism:

Metabolism Catabolism and anabolism Catabolism (breakdown) of lipids for energy into 2 carbon units Ketosis if fat catabolizes quickly due to lack of glucose, the liver cells partially oxidize fatty acids form ketone bodies Anabolism (synthesis) of lipids, or lipogenesis result in formation of tricglycerides , phospholipids, cholesterol Regulated by hormones Insulin, growth hormone, ACTH, Glucortioids 12

Fat Intake and Issues Fat Content of Foods:

Fat Intake and Issues Fat Content of Foods High-fat foods = high-calorie foods recommend 20%-35% kcal from fats with ≥10% of kcal from saturated fats Children younger than 5 years of age require at least 20% of kcal as fat MyPyramid emphasizes oils from fish and plants 13

Preserving Fats in Foods:

Preserving Fats in Foods Hydrogenated and emulsified fats and oils Oxidation of unsaturated fats Prevent damage that can make them rancid Hydrogenation makes fat more solid and stable Cis and trans fatty acids Relationship of trans fatty acids to elevated cholesterol levels Trans fatty acid content mandatory on food labels 14

Food Cholesterol vs. Blood Cholesterol:

Food Cholesterol vs. Blood Cholesterol Sources of dietary cholesterol Sources of blood cholesterol High blood cholesterol associated with high risk for coronary artery disease (CAD) 15

Food Cholesterol vs. Blood Cholesterol, cont’d:

Food Cholesterol vs. Blood Cholesterol, cont’d Lipoproteins Chylomicrons Very low-density lipoproteins (VLDLs) Low-density lipoproteins (LDLs) High-density lipoproteins (HDLs) Plaque formation High LDL increases CAD risk; high HDL decreases risk Total blood cholesterol = LDL + HDL 16

Blood Cholesterol Levels:

Blood Cholesterol Levels Blood Cholesterol Levels Risk Classification Total Cholesterol LDL Cholesterol Desirable <200 mg/dL <130 mg/dL Borderline-high 200-239 mg/dL 130-159 mg/dL High  240 mg/dL  160 mg/dL Modified from National Cholesterol Education Program: ATP III guidelines at-a-glance quick desk reference, NIH Pub No 01-3305, Washington, DC, 2001, U.S. Department of Health and Human Services; Public Health Service; National Institutes of Health; National Heart, Lung, and Blood Institute. •LDL: 70-130 mg/dL (lower numbers are better) •HDL: more than 40-60 mg/dL (high numbers are better) •Total cholesterol: less than 200 mg/dL (lower numbers are better) •Triglycerides: 10-150 mg/dL (lower numbers are better) 17

Overcoming Barriers:

Overcoming Barriers Energy intake Fat is more efficient being stored in body than CHO and protein Relationship between dietary fat and body fat 18

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Extreme dietary fat restrictions Dietary intake of fat can get too low Dietary fat still needed for vitamins and EFAs Health hazards related to restricted fat intake Failure to thrive; eating disorders, malnutrition Reduced intake of other nutrients High fat foods low in fiber and other nutrients 19

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Dietary fat intake and diet-related diseases Coronary artery disease (CAD) Saturated fat and heart disease Prevalence of high blood cholesterol(50% of US) Risk factors Health guidelines 20

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Cancer Breast cancer Colon cancer Prostate cancer 21

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Type 2 diabetes mellitus and hypertension Type 2 DM and hypertension indirectly related to fat intake Both disorders affect circulatory system; high dietary fat intake may limit function through risk of atherosclerosis Both disorders managed better when weight moderation is achieved; dietary fat reduction may enhance this process 22

Toward a Positive Nutrition Lifestyle: Gradual Reduction:

Toward a Positive Nutrition Lifestyle: Gradual Reduction The most effective way to achieve permanent behavior change is through gradual reduction An action plan for gradual reduction (small changes in behavior or food intake) provides structure for achieving goals 23

Substitute for High-fat Ingredients:

Substitute for High-fat Ingredients Nonfat milk Evaporated(skim) canned milk Yougurt Wine, lemon juice, broth Part-skim low-fat cheeses Cornstarch Water-packed canned fish, meats Whole-milk Cream Sour cream Butter Whole-milk ricotta Egg yolk Oil-packed canned fish 24

PowerPoint Presentation:

1. Which of the following has a high amount of saturated fat? a. Almonds b. Egg yolk c. Kidney beans d. Olive oil 25

PowerPoint Presentation:

Which of the following lipoproteins carry cholesterol from the liver to body cells? A desirable blood level for this lipoprotein is below 130 mg/ dL . a. High-density lipoprotein b. Chylomicron c. Total cholesterol d. Low-density lipoprotein 26

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