NTR 213 Chapter 5 Notes
NTR 213 Chapter 5 Notes NTR 213
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This 5 page Class Notes was uploaded by bjwall on Tuesday September 27, 2016. The Class Notes belongs to NTR 213 at University of North Carolina - Greensboro taught by Dr. Seth Armah in Fall 2016. Since its upload, it has received 5 views. For similar materials see Introduction to Nutrition in Nutrition at University of North Carolina - Greensboro.
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Date Created: 09/27/16
Chapter 5 – Lipids: Fats, Phospholipids, and Sterols 5.1 Fats in Our Food Fats in our food contribute to the texture, aroma, flavor o Fat gives ice cream its smooth texture and rich taste Fats add more calories than other nutrients (9 Cal/gram) America’s Changing Fat Intake Number of grams of fat Americans consume daily has changed little o What has changed: energy intake Types of fat in diet as well as the overall dietary pattern have greater impact on chronic disease risk than total fat intake. o High intakes of saturated fat from meat and dairy products, and trans fat used in shortening and margarine and added to processed foods are associated with a higher incidence of heart disease and certain types of cancer. o Diets high in unsaturated fats from fish, nuts, and veggie oils protect against chronic disease. 5.2 Types of Lipids Lipids are substances that do not dissolve in water. Triglyceride – major type of lipid in food and the body, consisting of 3 fatty acids attached to a glycerol molecule o Make up most of lipids in our food and in bodies o Fatty Acid – (structure of triglyceride) - molecule made up of a chain of carbons linked to hydrogens, with an acid group at one end of the chain Phospholipids – type of lipid whose structure includes a phosphorus atom Sterol – type of lipid with a structure composed of multiple chemical rings Triglycerides and Fatty Acids Fatty acids determine its function in the body and the properties it gives to food Fatty acids what we are really talking about when we refer to trans fat or saturated fat – really mean trans fatty acids and saturated fatty acids o Saturated Fatty Acids – fatty acid in which the C atoms are bonded to as many H atoms as possible; it therefore contains no C-C double bonds Saturated and Unsaturated Fatty Acids Unsaturated Fatty Acids – fatty acid that contains one or more C-C double bonds; may be either monounsaturated or polyunsaturated o # and location of the double bonds affect the characteristics that fatty acids give to food and the health effects they have in the body Saturated fatty acids have straight C chains that pack tightly together (high in SFA such as beef, butter, lard, tend to be solid at room temp) Unsaturated fatty acids have bent chains (higher in UFA such as corn, safflower, sunflower oils, tend to be liquid at room temp) o These are susceptible to spoilage or rancidity because bonds easily damaged by oxygen o High in UFA are associated with a lower risk of heart disease # and location of single (saturated) and double (unsaturated) C-C bonds affect its physical properties. Types of fatty acids in triglyceride determine its texture, taste, and physical characteristics. Saturated – one end: 3 H 1 C, other end: acid group (COOH) to C o Each C attached to 2 H so only single bonds b/n C o Red meat, butter, cheese, whole milk, palmitic acid Unsaturated – adjacent C in the C chains of fatty acid have 1 H, double bond b/n C o Unsaturated b/c not all C atoms are saturated w/ H atoms Monounsaturated – 1 C-C double bond Canola, olive & peanut oils, nuts, avocado, oleic acid Polyunsaturated – more than 1 C-C double bond Omega – 6: double bond occurs b/n 6 & 7 C atoms o Corn oil, safflower oil, soybean oil, nuts Omega – 3: double bond occurs b/n 3 & 4 C atoms o Flax seed, canola oil, nuts Essential Fatty Acids – a fatty acid that must be consumed in the diet because it cannot be made by the body or cannot be made in sufficient quantities to meet the body’s needs Plant oils are generally low in saturated fatty acids Tropical Oils – term used in the popular press to refer to the saturated plant oils – coconut, palm, and palm kernel oil – that are derived from plants grown in tropical regions o Types of saturated fats they do contain do not increase risk of heart disease and may have some health benefits Trans fatty acids Bonds in UFA can occur in the cis or trans configuration. Small amounts of trans fatty acids occur naturally, and larger amounts are generated by hydrogenation. Hydrogenation – process used to make partially hydrogenated oils in which H atoms are added to the C-C double bonds of unsaturated fatty acids, making them more saturated. Trans fatty acids are formed during the process o Makes unsaturated oils more saturated o Used to solidify veggie oils into hard margarine and shortening o Transforms some double bonds from cis to trans configuration, increases risk of heart disease, use of partially hydrogenated oils has been declining Orientation of H atoms are C-C double bond distinguishes cis from trans Phospholipids Present in small amounts, important in food and in body b/c allow water and fat to mix. Emulsifiers – a substance with both water-soluble and fat-soluble portions that can break fat into tiny droplets and suspend it in watery fluid o ex: egg yolks allow oil & water in cake batter to mix glycerol backbone, 2 fatty acids Phosphate Group – chemical group consisting of 1 phosphorus atom and 4 O atoms o Fatty acid tails – lipophilic, heads are hydrophilic Surround droplets of oil, allowing them to remain suspended in watery environment Lipid Bilayer – 2 layers of phosphoglyceride molecules oriented so that the fat-soluble fatty acid tails are sandwiched b/n water soluble phosphate- containing heads Lecithin – phosphoglyceride composed of glycerol backbone, 2 fatty acids, phosphate group, and molecule of choline; often used as an emulsifier in foods o Eggs and soybeans – natural sources of lecithin o Prevent oil from separating from other ingredients o In body, major constituent of cell membranes o Used to synthesize neurotransmitter acetylcholine, which activates muscles and memory Sterols Cholesterol – a sterol, produced by liver and consumed in the diet, which is needed to build cell membranes and make hormones and other essential molecules o Not essential in diet o 90% found in cell membranes o Only found in foods from animal sources Plant sterols help form plant cell membranes 5.3 Absorbing and Transporting Lipids Digestion and Absorption of Lipids Most fat digestion and absorption happens in small intestine; bile acids act as emulsifiers, breaking down large lipid droplets Monoglycerides – glycerol molecule with one fatty acid attached Micelle – particle formed in small intestine when products of fat digestion are surrounded by bile acids. It facilitates the absorption of lipids o Bile acids absorbed and returned to liver for reuse Transporting Lipids in the Blood Lipids consumed in diet are absorbed into intestinal mucosal cells From there, small fatty acids absorbed into blood, travel to liver Long chain fatty acids, cholesterol, fat-soluble vitamins packaged for transport Lipoprotein – particle that transports lipids in the blood Transport from the Small Intestine Chylomicron – lipoprotein that transports lipids from mucosal cells of small intestine and delivers triglycerides to other body cells o Too large to enter capillaries in small intestine, pass into lymph, which then delivers them to blood Transport from the Liver Lipids are transported from liver in very-low-density lipoproteins (VLDLs). o Circulate in blood, delivering triglycerides to body cells o 2/3 of these particles are returned to liver, rest transformed in the blood into: o Low-Density Lipoproteins (LDLs) – lipoprotein that transports cholesterol to cells Contain higher proportion of cholesterol Primary cholesterol delivery system for cells High levels – heart disease “bad cholesterol” 5.4 Lipid Functions Lipids necessary to maintain health Most are triglycerides stored in adipose tissue, which is body fat that lies under the skin and around internal organs o Lightweight energy storage molecule, cushion organs, insulate from temp changes Essential Fatty Acids Fatty acids linoleic acid (omega-6) and alpha-linoleic acid (omega-3) considered essential fatty acids (we cannot synthesize these) o Formation of phospholipids that give cell membranes their structure and functional properties. Essential for growth, development, and fertility, as well as maintaining structure of red blood cells and cells in skin and nervous system. Essential Fatty Acid Deficiency – condition characterized by dry, scaly skin and poor growth that results when the diet does not supply sufficient amounts of linoleic acid and alpha-linoleic acid o Symptoms – liver abnormalities, poor wound healing, impaired vision and hearing, growth failure in infants Eicosanoids – regulatory molecules that can be synthesized from omega-3 and omega-6 fatty acids o Help regulate blood clotting, BP, immune function o Omega-6 fatty acid arachidonic acid is starting material - increases blood clotting o When omega-3…-decreases blood clotting Fat as a Source of Energy Fasting and feasting 5.5 Lipids in Health and Disease Heart Disease Cardiovascular disease is any disease that affects heart and blood vessels; #1 cause of death for men and women in US Atherosclerosis – type of cardiovascular disease that involves the buildup of fatty material in artery walls o Reduce artery wall elasticity, blocking flow of blood o Development linked to dietary patterns that higher in cholesterol, sat fat, and trans fat and lower in unsat fats and fiber How atherosclerosis develops Inflammation drives formation of: Atherosclerotic Plaque – cholesterol-rich material that is deposited in the arteries of individuals with atherosclerosis o Process begins with injury, and response to this injury causes changes in lining of artery wall Diet and heart disease risk Antioxidants – substance that decreases adverse effects of reactive molecules o Decrease oxidation of LDL cholesterol – prevent development of plaque in artery walls 5.6 Meeting Lipid Needs Fat and Cholesterol Recommendations DRIs – 20-30% of calories for adults AI – linoleic acid – 12 g/day women, 17 for men AI – alpha LA – 1.1 g/day women, 1.6 men
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