Lipids January 24th 2011 Lipids Do not readily dissolve in water Types of lipids Triglycerides Phospholipids Sterols Cholesterol Fats solid and oils liquid 9 kcal gm 3500 kcal 1 pound of fat Fatty Acids Found in our body and foods In triglycerides Saturated fatty acids Solid form Unsaturated fatty acids Liquid form Cis and Trans unsaturated Fats are composed of both saturated and Composition of Common Fats Oils Functions of Fatty Acids Provide energy 9 kcal g Efficient storage of energy Insulation Protection Transport fat soluble vitamins Some satiety Flavor and mouth feel Recommendations for Fat Intake No RDA AHA recommendations 20 30 of total kcal from fat 7 10 can come from saturated trans fat 200 300 mg cholesterol day Average U S intake 33 of total kcal from fat 13 of kcal from saturated fat 180 320 mg cholesterol day Advice from National Cholesterol Education Program and Food and Nutrition Board Up to 35 of total kcal from fat Keep saturated fat cholesterol and trans fat to a minimum Saturated Fatty Acid Structure H H H H H H H H H H H H H H H H H O H C C C C C C C C C C C C C C C C C C OH H H H H H H H H H H H H H H H H H omega end Degree of saturation single carbon bond alpha end Monounsaturated Fatty Acid Structure H H H H H H H H H H H H H H H O H C C C C C C C C C C C C C C C C C C OH H H H H H H H H H H H H H H H H H omega end One double bond alpha end Polyunsaturated Fatty Acid Structure H H H H H H H H H H H H H O H C C C C C C C C C C C C C C C C C C OH H H H H H H H H H H H H H H H H H omega end 2 double bonds alpha end Chemical Forms of Common Lipids Triglycerides Most common form of fats and oils Fatty acids attached to a glycerol Glycerol 3 FA s Triglyceride 3 H20 Phospholipids Built on a glycerol backbone Contains phosphorus compound s Found in body Synthesized by the body as needed Functions of Phospholipids Component of cell membrane Emulsifier Bile acids Lecithins Improves food products Found in wheat germ peanuts yolks soy beans organ meat Sterols Multi ringed structure Do not have a glycerol backbone Waxy substance Do not readily dissolve in water Found in animal foods eggs etc Ex Cholesterol Vitamin D3 adrenal hormones sex hormones Functions of Cholesterol Essential component of cell membrane Produced by the liver Found only in animal products Forms important hormones Estrogen testosterone vitamin D Precursor to bile acids Lipids in Foods Emulsifiers Rancidity Decomposed oils Breakdown of the C C bonds by UV light and or O2 Unpleasant odor and flavor PUFA more susceptible Limited shelf life Prevention of Rancidity Hydrogenation Addition of vitamin E Addition of Butylated hydroxyanisol BHA and Butylated hydroxytoluene BHT Hydrogenation of Fatty Acids Process used to solidify an oil Addition of Hydrogen to C C double bonds Reduces the amount of double bonds in polyunsaturated fats Hydrogenation Cis and Trans Fatty Acid Synthetic Trans Fat Hydrogenation of monounsaturated and polyunsaturated fats partially hydrogenated oil Why Increase solidity of fat at room temp Increases shelf life and flavor stability of foods Where is Trans fat Partially hydrogenated fats Limit hydrogenated foods trans fat partially hydrogenated oil in ingredient list 0g trans fat doesn t always mean 0g History of Trans Fats 1910 hydrogenation began in U S 1912 Crisco marketed as first hydrogenated product replacing lard 1950s fast food industry bakeries snack foods begin to use trans fats Risks From Trans Fats Worsen risk factors for CVD Elevate LDL bad cholesterol Lower HDL good cholesterol Increase abdominal adipose mass Increase risk of CVD Trans fat intake Current Intake 3 4 total kcal Since 2006 FDA requires trans fat content on labels Elimination of trans fats by your choices Limit use of hydrogenated fats Limit deep fried foods Limit high fat baked goods Limit use of non dairy creamers Trans fat intake Elimination of trans fats by others Manufacturers eliminating partially hydrogenated fats Fast food restaurants eliminating trans fat New York City restaurants food distributors Wal Mart delis Return to using Saturated fats Digestion of Fat in the Mouth and Stomach Mouth Lingual lipase minor role in adults active in infants to digest the SCFA and MCFA in milk Can continue digestion in the stomach to hydrolyze triglyceride to diglyceride as it is acid stable Stomach Gastric lipase only hydrolyzes a small amount of fat Only minor digestion Gastric lipase Activated by an acidic environment Acts on triglycerides containing short and medium chain fatty acids Digestion of Fat in the Small Intestine Primary site of fat digestion Hormone Cholecystokinin CCK Stimulates release of pancreatic lipase major role in fat digestion Intestinal lipases minor role released Bile acid released Emulsifies digested fat Enterohepatic circulation Digestion of Fat in the Small Intestine Fat is broken down Triglycerides monoglycerides and fatty acids Phospholipids to glycerol fatty acids and remaining parts Sterols absorbed Absorption of Fat 95 of dietary fat is absorbed Diffused into the absorptive cells Glycerol Short and medium chain 12 C fatty acids Are water soluble Diffuse the membrane Enter the portal system Absorption of Fat Long chain fatty acids NOT water soluble Form micelles Diffuse the membrane re form into triglycerides after diffusion Triglycerides cholesterol and protein form chylomicron packages Enter the lymphatic system Water blood and oil fat are incompatible Composition and Roles of Lipoproteins Transportation of Absorbed Fatty Acids in blood stream Chylomicrons transported in blood Lipoprotein lipase LPL Break down TG on outside of cell MG s Glycerol Fatty Acids enter cell TG reassembled in cell Chylomicron remnant delivered to the liver Storage adipose tissue Unlimited space Store until needed for energy 9 kcal g Transportation of Synthesized Fat Made primarily by the liver Chylomicrons largest and least dense Mostly TG s Lipoproteins VLDL very low density lipoproteins LDL low density lipoproteins Few TG lots of Cholesterol HDL high density lipoproteins Picks up cholesterol etc from cells Lipoproteins High Density Lipoprotein HDL Synthesized by liver and intestine High proportion of protein Picks up cholesterol from dying cells and other sources Transfers cholesterol to other lipoproteins Transfers cholesterol directly back to the liver Benefits of a high HDL level Removes cholesterol from the bloodstream HDL may block oxidation of LDL Reduces risk of cardiovascular disease Pre
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