2/21/17 What Are Lipids? Chapter 5 Lipids: Not Just Fat BIOL 103 SP2017 Lipids Include… •  Triglycerides (most abundant lipids) – In body: stored in adipose Bssue – In food: “fats and oils” •  Phospholipids (~2% of dietary lipids) – Plant and animal origin – Body can make them – Soluble in fat and water •  Sterols (very, very small % of lipids) – Most well known: Cholesterol •  EssenBal nutrients – Provide energy – Help transport fat-­‐soluble nutrients throughout the body – Contribute greatly to the flavor and texture of food Fa\y Acids Are Key Building Blocks •  Fa\y acid – Determines whether a fat is _____ or ______ at room temperature –  Basic structure:
(-COOH); (-CH3)
1 2/21/17 Fa\y Acids Are Key Building Blocks •  Chain length – Fa\y acids differ in chain _________ – Lengths vary from 4 to 24 carbons – Grouped as short-­‐
chain, medium-­‐
chain, and long-­‐
chain Fa\y Acids Are Key Building Blocks •  Chain Length – Shorter fa\y acids remain _______ at room temperature and even with refrigeraBon – Shorter fa\y acids also are more ________-­‐soluble Fa\y Acids Are Key Building Blocks •  SaturaBon –  Saturated fa.y acids •  All ______ bonds between carbons –  Unsaturated fa.y acids •  One or more carbon bonds is a ________ bond 1.  Monounsaturated fa.y acid (MUFA) 2.  Polyunsaturated fa.y acid (PUFA) –  Fats with more double bonds are generally more ____________ 2 2/21/17 Saturated vs. Unsaturated Fat Fa\y Acids Are Key Building Blocks Saturated vs. Unsaturated/Cis vs. Unsatruated/Trans Fats •  Cis vs. trans – Unsaturated fa\y acids can vary in shape – Cis fa.y acids •  Chain is _________ •  Occur naturally – Trans fa.y acids •  Chain is straighter •  Produced by _______________ 3 2/21/17 Trans Fat •  In health, trans fa\y acids are known to raise LDL (“bad”) cholesterol, and lower HDL (“good cholesterol”), promote systemic inflammaBon, and increase triglycerides in your blood. •  History and how it is made: –  In Europe (1910): needed a cheaper bu\er subsBtute for soldiers –  In US (1960s): People wanted to eat a “healthier and cheaper bu\er” à food scienBsts decided to hydrogenate vegetable oil to solidify them Fa\y Acids are Key Building Blocks •  NonessenBal and essenBal fa\y acids 1.  NonessenBal fa.y acids •  Can be made in the body •  Not “essenBal” to have in your diet • 
What are the posiBve and negaBve consequences of hydrogenaBng a fat? OxidaBon causes food to spoil and d amage body Bssues Pros Cons 1.  Longer shelf life 1.  More saturated fat 2.  Improved texture and taste 2.  Creates trans fat Fa\y Acids Are Key Building Blocks •  EssenBal and NonessenBal Fa\y Acids 2.  EssenBal fa.y acids •  Must come from food •  Cannot be made by the body •  Two families: – Omega-­‐3 (alpha-­‐linolenic acid) – Omega-­‐6 (linoleic acid) •  Pre-­‐cursors to eicosanoids 4 2/21/17 Triglycerides •  Structure – Glycerol + 3 fa\y acids – Most fa\y acids exist as part of triglyceride molecules Triglycerides Apple vs. Pear •  FuncBons 1.  Energy source: 9 kcal/g 2.  Energy reserve: form of stored energy in adipose Bssue 3.  InsulaBon and protecBon: 1.  Visceral fat 2.  Subcutaneous fat 4.  Carrier of fat-­‐soluble nutrients 5.  Sensory qualiBes (flavor, odor, texture) in food 5 2/21/17 Triglycerides in Food •  Found in a variety of fats and oils •  Classified by their most prevalent type –  Saturated fa\y acids: _________ foods and tropical oils –  Polyunsaturated fa\y acids: plant or animal based •  Omega-­‐3: soybean, flaxseed oils; salmon, tuna •  Omega-­‐6: seeds, nuts, corn oil, meat, poultry, eggs Phospholipids •  Structure – Glycerol + two fa\y acids + phosphate group – CompaBble with both fat and water: “ideal emulsifier” •  Keep fat suspended in water •  Keep oil and water mixed Phospholipids FuncBons 1.  Perfect _________ element for cell membranes – Able to communicate with watery environments of blood and cell fluids – SelecBvely allow both fa\y and water-­‐soluble substances into the cell – Store fa\y acids temporarily 6 2/21/17 Phospholipids FuncBons 2.  Role in Fat DigesBon and Transport – Mouth and Stomach •  Break fats into Bny parBcles for digesBon – IntesBne •  ConBnue emulsifying fat – Blood •  Coat the surface of the lipoproteins that carry lipid parBcles to their desBnaBons in the body Phospholipids FuncBons Emulsifier (lecithin) in food industry Lecithin is a blend of phospholipids with different nitrogen-­‐containing compounds •  FuncBon: –  Used as an emulsifier to combine two ingredients that don’t ordinarily mix, such as oil and water (e.g. salad dressing) •  Can be used in high-­‐fat powered products (e.g. dry milk, coffee creamers, milk replacers) helps mix fa\y compounds with water Soy Lecithin: creaminess, longer shelf life, soQeners, “anB-­‐sBckiness” Phospholipids FuncBons •  Emulsifiers (__________) – in the human body… •  Lecithin is a phospholipid with choline •  Role: – Forms _______ which are used to emulsify fats during digesBons Phospholipids in Food •  Occur naturally in plants and animals, but in much smaller amounts than triglycerides •  Abundant in egg yolks, liver, soybeans, peanuts •  Not a dietary essenBal (since our body can make it) 7 2/21/17 Sterols •  A category of lipids that include cholesterol •  Structural characterisBcs: –  MulBple ring structure –  Contain no fa\y acids Sterols •  Cholesterol funcBons: 1.  Structural component of cell membranes 2.  Precursor to other substances •  Examples: Vitamin D, Sterol Hormones, bile salts •  Cholesterol synthesis in ______________ •  Sterols in food –  Found in animal and plant foods Does Plant Sterols Help Reduce Blood Cholesterol? 8 2/21/17 Lipid DigesBon and AbsorpBon •  DigesBon of Triglycerides and Phospholipids –  Mouth •  Chewing and lingual lipase –  Stomach •  Breaks triglycerides via gastric lipase down to diglycerides and free fa\y acids –  Small intesBne •  Bile and pancreaBc lipase emulsify and break down the fats for absorpBon •  IntesBnal cells absorb glycerol and short-­‐
chain fa\y acids into the bloodstream Lipid DigesBon and AbsorpBon Lipid DigesBon •  Small IntesBne (cont.) – Bile salts form micelles (water-­‐soluble globules with a fa\y core) to carry long chain fa\y acids to the microvilli – Bile salts return to the ______ to be used again •  Enterohepa1c Circula1on 9 2/21/17 Lipid AbsorpBon •  To travel in the bloodstream, lipids are packaged into _________________ carriers •  Lipoprotein leave the intesBnal cell as _____________________ •  Deliver dietary lipids from intesBnes to cells and liver •  Chylomicron goes to lymph system (lacteals) à bloodstream TransportaBon of Lipids in the Body •  Lipids packaged into lipoprotein carriers in order to travel in the bloodstream •  Lipoproteins differ by size, density, and the composiBon of their lipid cores: –  VLDL –  IDL –  LDL –  HDL Lipids in the Body 1.  Very-­‐low-­‐density lipoproteins (VLDL): –  Deliver ________________ to cells 2.  Intermediate-­‐density lipoproteins (IDL) –  Returns to liver and is converted to LDL 3.  Low-­‐density lipoproteins (LDL) –  Deliver _____________ to cells, which body uses to synthesize membranes, hormones, etc. –  Returns to liver aqerwards 4.  High-­‐density lipoproteins (HDL) –  Pick up cholesterol for removal or recycling 10 2/21/17 Lipoprotein Pathway Summary
OpBmal Levels of Cholesterol RecommendaBons for Fat Intake RecommendaBons for Fat Intake •  Recommended intake – Reduce saturated fat, trans fat, and cholesterol – Total fat: 20–35% of calories – Less than 10% of calories from saturated fat – 2010 Guidelines: Less than 300 mg per day of cholesterol •  EssenBal fa\y acid requirements – Linoleic acid/omega-­‐6 fa\y acids should provide about 2% of calories – Requirements for omega 3 fa\y acid is less well known •  Omega-­‐6 and omega-­‐3 balance – RaBo of ____omega-­‐6 to omega-­‐3 fa\y acids –  Why would it be bad to consume too much omega 3 fa\y acids? 11 2/21/17 RecommendaBons for Fat Intake •  Role of fat replacers – Different types of composiBon – Olestra: Sucrose + fa\y acids •  IndigesBble— provides no calories •  Reduces absorpBon of fat-­‐soluble vitamins Lipids and Health 1.  Heart disease/Cardiovascular Diseae –  Leading cause of death in US (1 death/
minute) –  Major risk factors: •  High blood cholesterol •  Smoking •  High blood pressure Lipids and Health 2.  Obesity – Determined by excessive accumulaBon of body fat leading to a body weight in relaBon to height that is significantly greater than some accepted standard. – High-­‐fat diets promote weight gain – Significant within the U.S. populaBon •  34.9% of American adults •  17% of American children and adolescents 12 2/21/17 Lipids and Health 3.  Metabolic syndrome – Affects ¼ of American adults – Cluster of at least three symptoms: •  Excess abdominal fat •  High blood glucose •  High serum triglycerides •  Low HDL cholesterol •  High blood pressure Lipids and Health •  Cancer – Dietary and lifestyle factors for reducing cancer risk •  Maintain a healthful weight •  Adopt a physically acBve lifestyle •  Consume a healthy diet •  Limit alcohol consumpBon Lipids and Health 4.  Cancer – Results from complex mix of lifestyle, hereditary, and environmental factors – Role of nutriBon and diet complex •  Evidence suggests 30-­‐40% are due to poor food choices and physical inacBvity •  Some dietary factors act as promoters, while others serve a protecBve role Lipids and Health •  Reducing heart disease risk –  AHA diet and lifestyle recommendaBons •  Consume an overall healthy diet •  Aim for a healthy body weight •  Aim for a desirable lipid profile •  Aim for normal blood pressure •  Aim for normal blood glucose levels •  Be physically acBve •  Avoid use of and exposure to tobacco products 13 2/21/17 Lipids and Health Lipids and Health •  Reducing heart disease risk –  AHA recommendaBons •  Balance calorie intake and physical acBvity to achieve or maintain a healthy body weight •  Consume a diet rich in fruits and vegetables •  Choose whole-­‐grain, high-­‐fiber foods •  Consume fish, especially oily fish, at least twice a week •  Limit your intake of saturated and trans fat and cholesterol •  Reducing heart disease risk –  AHA recommendaBons (cont.) •  Minimize your intake of beverages and foods with added sugars •  Choose and prepare foods with li\le of no salt •  If you consume alcohol, do so in moderaBon •  Follow the AHA recommendaBons when eaBng outside of the home Lipids and Health •  Puvng It All Together – Healthy People 2020 objecBves target reducing deaths from heart disease and stroke and reducing the number of adults with high blood cholesterol levels 14