Week 4 - Lipids
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This 7 page Class Notes was uploaded by rgslc8 on Friday September 16, 2016. The Class Notes belongs to Nutr 1020 at University of Utah taught by Anandh Babu Pon Velayutham in Fall 2016. Since its upload, it has received 10 views. For similar materials see Scientific Foundations of Nutrition and Health in Nutrition at University of Utah.
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Date Created: 09/16/16
Lipids 1 --- September 13 Important Terms All fat is not created equal Lipids Lipids are energy dense o Fatty acids from triglycerides yield 9Kcal/gram o Play vital roles (energy, membrane component, cell growth, insulation for organs, help the body absorb some nutrients and product important hormones) Lipids should comprise 20 to 35% of an adult’s total calorie intake Humans need very little fat in their diet to maintain health o Consumption of salmon has been linked to lower risk of several chronic diseases Chemistry of Lipids Carbon + Hydrogen + Oxygen (less oxygen atoms compared to carbohydrates) Lipids solid at room temperature – Fat Lipids liquid at room temperature – Oil They do not readily dissolve in water Classification of Lipids Fatty Acids o Basic unit of fat o Simplest form of lipids Triglycerides o Glycerol and 3 fatty acids o Primary form of lipids o Most common type of body found in body and foods Phospholipids o Glycerol + 2 fatty acids + phosphorus containing compounds Sterols o Cholesterol Fatty Acids Simplest form of lipids Chain of carbon, flanked by Hydrogen on each side CH2, COOH Acid group, CH3 Methyl group Stearic acid: CH3 – (CH2)16 – COOH Fatty acids can be saturated or unsaturated with hydrogen Saturated fatty acid and unsaturated fatty acid o Saturated: no double bonds o Unsaturated: double bonds Monounsaturated fatty acids (MUFA) One double bond Polyunsaturated fatty acids (PUFA) Two or more double bonds o Omega 3 PUFA o Omega 6 PUFA Saturated Fatty Acids Very straight and linear o Pack very close together, makes them solidify at room temperature Animal fats – high in saturated fatty acids – solid at room temperature o Beef fat o Chicken fat: less saturated fatty acid, semi solid Saturated fat can be deposited within the blood vessels and eventually block blood flow Unsaturated Fatty Acids If carbon chain of FA contains double bond – those carbons in chain have fewer bonds to share with hydrogen, the chain is said to be unsaturated Double bonds create kinds in their structure cannot pack together closely liquid at room temperature Monounsaturated Fatty Acids Unsaturated FA with only one double bond Ex. Canola oil and olive oil contain high percentage of MUFA Polyunsaturated Fatty Acids Unsaturated FA with two or more of double bonds Ex. Corn, soybean, suflower oils are rich in PUFA o Omega 3 and Omega 6 rd Omega 3: the first double bond appears on the 3 carbon ALA(dark greens, soy bean oil, walnuts) EPA, DHA (Fish, fish oil, eggs, beef) o Health benefits: Lower risk of coronary heart disease Reduce triglycerides Required for brain and cardiovascular health Must be obtained through diet Omega 6: the first double bond appears on the 6 carbon Health benefits: o Reduce heart disease risk o Improve insulin resistance, reduce diabetes risk, lower blood pressure Must be obtained through the diet: 5-10% of calories Essential Fatty Acids Some fatty acids can be made by the body and therefore not needed in out diet Only certain PUFA are essential parts of a diet Failure to consume enough essential fatty acid o Skin becomes flaky and itchy o Diarrhea o Other symptoms such as infection Trans Fat Unsaturated Fatty Acid – Two forms cis FA and trans FA Natural form – MUFA and PUFA are in cis form Food processing – hydrogens are transferred to opposite sides of the c-c double bond – creating trans form – trans fatty acids The Food and Nutrition Board suggests limiting intake of trans fatty acids in processed food as much as possible Cis fatty acids + partial hydrogenation = saturated fatty acid and trans fatty acid Why companies use trans fat o Easy to use o Inexpensive to produce and lasts a long time o Gives food desirable taste and texture Trans Fat and Food Label If the product contains less that 0.5g of trans fat per serving, the manufacturers are permitted to label as 0g trans fat o Look for “partially hydrogenated oil” in the ingredients list to spot the trans fat Hidden sources of trans fat: pizza, margarines, cookies, pie crusts, French fries, friend chicken, potato, corn, tortilla chips Americans ingest about 5 pounds of trans fat per year Industrial Trans fatty acids: increase the risk of heart disease cancer, and obesity “Natural” trans fatty acids Conjugated linoleic acid (CLA) o Beef, milk, butter Sterols Class of lipids with a characteristic multi-ringed structure Structurally and functionally different from fatty acids, triglycerides, phospholipids Cholesterol Good Fat Increase good cholesterol Decrease bad cholesterol Lipids 2 --- September 15 Lipids in Foods 1. Triglycerides o Glycerol backbone and 3 fatty acids 2. Phospholipids o Contains phosphorus containing compounds and fatty acids and glycerol 3. Cholesteryl ester o Cholesterol and fatty acids Fats and oils – Functions as components of foods Flavor and texture to foods Provide some satiety after meals Digestion of Lipids Stomach – gastric lipase (act on TG with small chain fatty acid) Pancreas – pancreatic lipase (act in small intestine and requires bile) Emulsion – mixture of oil and water Bile: nature emulsifier o Helps in fat digestion and absorption o Secreted by liver and stored in the gall bladder o Suspends lipids in the watery digestive juices o Emulsification breaks large fat globules into smaller fat droplets The total surface area for lipase action increases Improves fat digestion and absorption Digestion Mostly done in small intestine o Primary site for digestion and absorption Absorption Intestinal villi Carrying Lipids in the Blood Stream (Transport of Lipids) Fat and water do not mix easily Lipoproteins serve as vehicles for transportation of lipids from the small intestine and liver to the body tissue o Lipids + proteins = Lipoproteins Shell composed of protein Phospholipids and cholesterol Lipoproteins Four groups o Chylomicrons More triglycerides o Very Low Density Lipoproteins (VLDL) More triglycerides o Low Density Lipoprotein (LDL) More cholesterol o High Density Lipoprotein (HDL) More protein Lipids are less dense than proteins o High lipids and low protein = low density (LDL) o Low lipids and high protein = high density (HDL) LDL: Bad Cholesterol Transport cholesterol from liver to other parts of the body: stores cholesterol in the blood stream HDL: Good Cholesterol Picks up extra cholesterol and takes it back to liver where it is metabolized o Roams the blood stream, picking up cholesterol from dying cells and other sources Cholesterol is cholesterol. It becomes “good” or “bad” based on if HDL or LDL carries it. High amounts of LDL increase the risk of CV disease High amounts of HDL reduce the risk of CV disease Lipemia: fat in the blood Roles of Lipids in the Body Providing Energy o Triglycerides stored in adipose tissue: main fuel for musecles o Cells need a supply of carbohydrates to efficiently process fatty acids for fuel Storing energy for later use o Energy stored mainly in the form of triglycerides o Adipose cells – its fat storage sites can increase about 50 times in weight o If the amount of fat to be stored exceeds the ability of the existing cells to expand, the body can form new adipose cells Capacity to store fat in the body is essentially limitless Regular lean adult: 35 billion adipocytes Extremely obese adult: 120 billion adipocytes Insulating and protecting the body o Insulating later of fat just beneath the skin is made up of triglyceride o Surrounds and protects organs Transporting fat soluble vitamins o Carry fat soluble vitamins to small intestine and aid their absorption Cholesterol Form important hormones/vitamins o Female sex hormones – estrogen o Male sex hormones – testosterone o Building blocks of bile acids o 2/3 cholesterol is made in the body Need 1/3 from diet Phospholipids Many found in the brain Participate in fat digestion (emulsifier) Recommendations for fat intake 20-35% of total calories Cholesterol should amount to a maximum of 300 mg per day Body Fat % Lean: men (9-12%) women (19-22%) o Excellent for health and longevity o Risky men more than 30%, women more than 40% o Risky men less than 5%, women less than 15% Measuring body fat o BOD POD
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