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The Lipids: Triglycerides, Phospholipids, and Sterols
Chapter 5
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Introduction Poor health Family of lipids Too much fat Too little fat
Too much of some kinds of fat Family of lipids Triglycerides Phospholipids Sterols
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Chemist’s View of Fatty Acids and Triglycerides
Energy provided per gram More carbons and hydrogens Preview of lipids Triglycerides: glycerol and 3 fatty acids Fatty acids: even number of carbons Fatty acids: saturated or unsaturated Omega-3 and omega-6 fatty acids
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Chemist’s View of Fatty Acids and Triglycerides
Organic acid Methyl group at one end; acid group at other end Usually even number of carbons 18-carbon fatty acids abundant in food Saturations Saturated – full of hydrogens Unsaturated – missing hydrogens
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Chemist’s View of Fatty Acids and Triglycerides
Location of double bonds Nearest the methyl end of the carbon chain Omega number Linolenic acid Monounsaturated fatty acids Omega-9 groups
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Chemist’s View of Fatty Acids and Triglycerides
Glycerol backbone Three fatty acids Formed via series of condensation reactions Usually contain mixture of fatty acids
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Chemist’s View of Fatty Acids and Triglycerides
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Chemist’s View of Fatty Acids and Triglycerides
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Chemist’s View of Fatty Acids and Triglycerides
Degree of unsaturation Firmness Polyunsaturated fats Saturated fats Length of carbon chain Stability Oxidation and spoilage of fats
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Chemist’s View of Fatty Acids and Triglycerides
Degree of unsaturation Hydrogenation Advantages Trans-fatty acids Configurations – cis and trans Similarity to other types of fat
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Chemist’s View of Fatty Acids and Triglycerides
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Chemist’s View of Fatty Acids and Triglycerides
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Chemist’s View of Phospholipids and Sterols
Solubility in fat and water Emulsifiers in food industry Lecithin Food sources Roles Part of cell membranes Emulsifiers
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Chemist’s View of Phospholipids and Sterols
Food sources Cholesterol Plant sterols Roles of sterols Body compounds made from cholesterol
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Lipid Digestion Fats are hydrophobic Goal of fat digestion
Digestive enzymes are hydrophilic Goal of fat digestion Dismantle triglycerides Monoglycerides, fatty acids, and glycerol
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Lipid Digestion
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Lipid Digestion Mouth Stomach Lingual lipase
Strong muscle contractions Gastric lipase
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Lipid Digestion Small intestine Bile routes Cholecystokinin (CCK)
Gall bladder releases bile Bile acts as emulsifier Pancreatic lipase Hydrolysis Triglycerides and phospholipids Bile routes Blood cholesterol levels
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Emulsification of Fat by Bile
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Hydrolysis of a Triglyceride
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Enterohepatic Circulation of Bile
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Lipid Absorption Directly into bloodstream Lymphatic system
Glycerol and short- & medium-chain fatty acids Lymphatic system Micelles diffuse into intestinal cells Reassembly of triglycerides Packed with proteins – chylomicrons Bypass liver at first
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Absorption of Fat
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Lipid Transport Four main types of lipoproteins Chylomicrons
Largest and least dense Transport diet-derived lipids Liver removes remnants from blood Very-low-density lipoproteins (VLDL) Made in the liver Proportion of lipid shift
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Lipid Transport Health implications Four main types of lipoproteins
Low-density lipoproteins (LDL) Cell needs Liver regulation High-density lipoproteins (HDL) Remove cholesterol from cells Carry cholesterol to liver for recycling Anti-inflammatory properties Health implications
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Lipid Transport
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Role of Triglycerides Provide the cells with energy Adipose tissue
9 kcalories per gram Virtually unlimited ability to store fat energy in body Adipose tissue Secretes hormones Adipokines Skin insulation, shock absorption, cell membranes, and cell signaling pathways
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Essential Fatty Acids Linoleic acid – Omega-6 fatty acid
Sources Linolenic acid – Omega-3 fatty acid DHA EPA Eicosanoids Fatty acid deficiencies
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A Preview of Lipid Metabolism
Adipose cells store fat after meals Lipoprotein lipase Hydrolyzes triglycerides Triglycerides reassembled inside adipose cells Using fat for energy Protein sparing Energy deprivation Fasting and ketone bodies
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Health Effects of Lipids
Heart disease Elevated blood cholesterol Saturated fat – increase LDL cholesterol, promote blood clotting Dietary choices Trans-fats – increase LDL cholesterol Dietary cholesterol
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Health Effects of Lipids
Heart disease Monounsaturated fats Replace saturated and trans fats Reduces blood cholesterol Dietary sources Omega-3 fats Benefits Omega-6 to omega-3 ratio
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Health Effects of Lipids
Cancer Promotion rather than initiation of cancer Dietary fat and cancer risk Differs for various types of cancer Obesity Cutting fat from diet reduces kcalories Dietary recommendations
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Recommended Intakes of Fat
DRI and Dietary Guidelines Diet low in saturated and trans fat Diet low in cholesterol 20 to 35 percent of daily energy from fat AI set for linoleic and linolenic acids Daily Values (DV) on food labels Saturated fat and cholesterol Risk of insufficient fat intake
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From Guidelines to Groceries
Fat-soluble vitamins A, D, E, and K Flavor, texture, and palatability Meats and meat alternatives Selections Milk and milk products
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From Guidelines to Groceries
Vegetables, fruits, and grains Lowers consumption of various fats in the diet Invisible fat Fried and baked goods Choose wisely Unprocessed foods
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From Guidelines to Groceries
Fat replacers Types Risks Read food labels Total fat, saturated fat, trans fat, and cholesterol Compare products % Daily Value vs. % kcalories from fat
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Butter and Margarine Labels Compared
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High-Fat Foods – Friend or Foe?
Highlight 5 High-Fat Foods – Friend or Foe?
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Guidelines for Fat Intake
Limit saturated fat and trans fat intake Moderate kcalories Enough fat for good health Not too much of the harmful fats DRI recommendations Compatible with low rates of disease
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High-Fat Foods and Heart Health
Olive oil Benefits for heart health Replace saturated fats Nuts LDL cholesterol Fat composition Cautious advice for dietary inclusion
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High-Fat Foods and Heart Health
Fish Omega-3 fatty acids Benefits for heart health Environmental contaminants Dietary recommendations
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High-Fat Foods and Heart Health
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High-Fat Foods and Heart Disease
Saturated fat and LDL cholesterol Sources of saturated fat in the U.S. Meats Whole milk products Tropical oils Zero saturated fat is not possible Trans fat Limit hydrogenated foods
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High-Fat Foods and Heart Disease
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High-Fat Foods and Heart Disease
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High-Fat Foods and Heart Disease
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The Mediterranean Diet
Traditionally Low in saturated fat Very low in trans fat Rich in unsaturated fat Rich in complex carbohydrate and fiber Rich in nutrients and phytochemicals Benefits for heart disease risk
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