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Lipids: Essential Energy-Supplying Nutrients

5. Lipids: Essential Energy-Supplying Nutrients. What Are Lipids?. Lipids Diverse group of molecules that are insoluble in water Fats The lipid content of diets and foods. What Are Lipids?. Three types of lipids are found in foods and in body cells and tissues: Triglycerides

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Lipids: Essential Energy-Supplying Nutrients

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  1. 5 Lipids: Essential Energy-Supplying Nutrients

  2. What Are Lipids? • Lipids • Diverse group of molecules that are insoluble in water • Fats • The lipid content of diets and foods

  3. What Are Lipids? • Three types of lipids are found in foods and in body cells and tissues: • Triglycerides • Phospholipids • Sterols

  4. Triglycerides • Triglycerides (triacylglycerides) contain: • Three fatty acid molecules • One glycerol molecule

  5. Triglycerides • Fatty acids are classified by: • Carbon chain length • Saturation level • Shape

  6. Triglycerides: Chain Length • Short-, medium-, or long-chain fatty acids • Carbons can be numbered • Carboxyl end (COOH): -carbon (alpha—first) • Methyl end (CH3): Ω-carbon (omega—last) • Determines method of lipid digestion, absorption, metabolism, and use

  7. Triglycerides: Saturation • Saturatedfatty acids have hydrogen atoms surrounding every carbon in the chain • Monounsaturated fatty acids lack one hydrogen atom (one double bond) • Polyunsaturated fatty acids have more than one double bond

  8. Triglycerides: Shape • Determined by the saturation of the carbon chains • Saturated fatty acids pack tightly together and are solid at room temperature • Animal fats, butter, and lard are high in saturated fatty acids

  9. Triglycerides: Shape • Unsaturated fatty acids do not stack together well and are more liquid at room temperature • Hydrogen atoms at the unsaturated part can be arranged in different positions: • Cis: same side of the carbon chain • Trans: opposite sides of the chain

  10. Triglycerides • Hydrogenation: hydrogen atoms are added to unsaturated fatty acids • Make oils more solid and more saturated • Create trans fatty acids • Reduce oxidation; resist rancidity • Increase risk of cardiovascular disease

  11. Triglycerides • Essential fatty acids: cannot be made by the body and must be obtained from food • Linoleic acid (omega-6 fatty acid) • Found in vegetable and nut oils • Alpha-linolenic acid (omega-3 fatty acid) • Found in vegetables, soy, flaxseeds, walnuts

  12. Triglycerides • Omega-3 fatty acids found in fish and fish oil • Eicosapentaenoic acid (EPA) • Docosahexaenoic acid (DHA) • Reduce risk of heart disease • Stimulate prostaglandins and thromboxanes that reduce inflammatory responses • Reduce blood clotting and plasma triglycerides

  13. Phospholipids • Phospholipids contain • Glycerol backbone, two fatty acids, phosphate • Soluble in water • Transport fat in the bloodstream • Manufactured in our bodies (not required)

  14. Sterols • Sterolscontain multiple rings of carbon atoms • Plant sterols appear to block the absorption of dietary cholesterol • Cholesterol is made in our bodies and therefore is not necessary in the diet • Sex hormones, vitamin D, bile

  15. Digestion of Fats • Fat digestion begins in the small intestine • Cholecystokinin (CCK) and secretin: gallbladder contractions release bile • Bile is produced by the liver and stored in the gallbladder • Bile emulsifies fat into small droplets • Pancreatic enzymes break fat into two fatty acids and a monoglyceride Fat Digestion

  16. Absorption of Fats • Lipoprotein transports lipids for absorption • Chylomicron: lipoprotein produced in intestine to transport lipids from a meal • Composed of fatty acids surrounded by phospholipids and proteins • Soluble in water

  17. Absorption of Fats • Chylomicrons are absorbed by cells of the small intestine, then: • Travel through the lymphatic system • Transferred to the bloodstream • Short- and medium-chain fatty acids are absorbed more quickly since they are not arranged into chylomicrons

  18. Absorption of Fats • Triglycerides in the chylomicrons must be disassembled by lipoprotein lipase before they can enter body cells • In body cells, triglycerides can be: • Used immediately for energy • Used to make lipid-containing compounds • Stored in muscle and adipose tissues Lipid Absorption

  19. The Roles of Fat • 9 kcal per gram • Major fuel at rest • Endurance exercise • Stored energy • Essential fatty acids • Fat-soluble vitamins • Regulates cell function • Maintains membrane • Protects the body • Provides flavors and textures of foods • Helps us feel satiated

  20. How Much Fat? • Acceptable Macronutrient Distribution Range (AMDR) for fat: 20−35% of calories • Minimize saturated and trans fatty acid intake to lower risk of heart disease • Active people may need more energy from carbohydrates and can reduce their fat intake to 20−25% of total calories

  21. How Much Fat? • Dietary Reference Intakes (DRIs) set for essential fatty acids • Linoleic acid: AMDR of 5−10% of energy • Alpha-linolenic acid: 0.6−1.2% of energy • 5:1 to 10:1 ratio of linolenic:alpha-linolenic acid • Saturated fat: less than 7% of energy • Trans fats: reduced to the absolute minimum

  22. Food Sources of Fat • Visible fats • Fats we add to foods • Butter, cream, mayonnaise, salad dressings • Invisible fats • Fats hidden within foods • Occur naturally or added during processing • Baked goods, dairy, meats, fast foods

  23. Food Sources of Fat • Beneficial fats • Omega-3 fatty acids may be low in diets • Fish, walnuts, soy, canola, flaxseed • Switching to more healthful fats without increasing total fat intake • Use olive or canola oil in place of butter or margarine • Select low-fat or nonfat dairy products

  24. Food Sources of Fat • Fat replacers • Used to lower fat content of foods • Found in chips, cakes, cookies • May cause GI side effects in large amounts • Example: olestra (Olean) Fats in Food

  25. Cardiovascular Disease • Cardiovascular disease • Dysfunction of the heart or blood vessels • Can result in heart attack or stroke

  26. Cardiovascular Disease • Risk factors for cardiovascular disease: • Being overweight • Physical inactivity • Smoking • High blood pressure • Diabetes mellitus • Inflammation

  27. Cardiovascular Disease • Dietary fats increase blood lipids • Highly saturated and trans fat intakes increase blood cholesterol • Omega-3 fatty acids reduce inflammation and blood triglycerides

  28. Cardiovascular Disease • Blood lipids include: • Chylomicrons—present only after a meal • Very-low-density lipoproteins (VLDL) • Low-density lipoproteins (LDL) • High-density lipoproteins (HDL) Lipoproteins: VLDL, LDL, and HDL

  29. Cardiovascular Disease • Diets high in saturated fats • Decrease the removal of LDLs from the blood • Increase blood cholesterol levels • Contribute to the formation of plaques that can block arteries

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