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Danny M.Pincivero

108 LECTURE - LIPIDS WHAT ARE LIPIDS?  Broad range of organic molecules that dissolve easily in organic solvents, but much less soluble in water. Vitamins A, D, E, K are lipid soluble; not soluble in water Classification: 1) Hydrophobic (“water-fearing”) 2) Lipophilic (“fat-loving”); fat molecules can move easily through membranes, no energy or transporters needed; just uses concentration gradient • Both classifications have different degrees of solubility MAIN CLASSES OF LIPIDS 1) Triglycerides (also called triacylglyerols) 2) Phospholipids 3) Sterols Quick facts: 1) Triglycerides • Lipid molecule from which we derive metabolic energy • Triglycerides are the storage form of fatty acids • Largest category, makes up most of the lipids • Plant and animal origin • Types of fatty acids in triglycerides vary depending upon food source and depending upon fatty acid, can have very diff effect on physiology – healthy or not • Efficient means of storing energy; no central storage for proteins but for carbs there are – glycerol • Water molecules are moved into cell when glucose is moved into cells as well – less efficient KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 109 2) Phospholipids • Makes up approximately 2% of all dietary lipids • Plant and animal sources • Soluble in fat and water • Major constituent of cell membranes • Involved in fatty acid transport (forms outer shell of chylomicrons and lipoproteins). o First line of absorption – mucosal cells in small intestine, they absorb fat very well, forms chylomicrons (phospholipid globules that store and transport triglycerides and cholesterol) o Lipoporoteins are chylomicrons assembled in a different stage, chylomicrons eventually transformed into lipoproteins, same function as chylomicrons o High levels of lipoproteins which carry cholesterol and triglycerides is detrimental to cardiovascular health 3) Sterols • Small percentage (<2%) • Most famous: cholesterol ( only in animal based foods, not plant based foods) • Precurosor to hormones (sex and cortisol), Vitamin D, and bile acids o All cholesterol derivatives, to make the above you need cholesterol FATTY ACIDS: Hydrocarbon chain (4-24 carbons) Short chain: <6 carbons Medium chain: 6-10 carbons Long chain: >12 carbons Fatty acid notation: 18:0 (# carbon atoms in that particular fatty acid : type of chem bonds between carbon atoms, 0 means there are 0 double bonds); 18:0 fatty acid is saturated, all potential binding sites are occupied; all chem connections are occupied by carbon or hydrogen atoms KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 110 Example: Butyric acid (4:0)……provides the flavour in butter. - Short chain, saturated Examples: Palmitic acid 16:0 Stearic acid 18:0*, chocolate, meat fats, solid at room temp Effect of chain length: Longer chain = more solid at room temperature; fatty acids for chem bonds with each other; the longer it is, the more chem bonds, more stacked on top, greater texture, more solid; heat breaks bonds and solid moves to liquid – phase change Shorter chain = more liquid at room temperature (oils) Types of fatty acids: 1) Saturated, all carbons are single bonded to adjacent carbons or 2 hydrogen atoms. 2) Monounsaturated (1 double bond): 3) Polyunsaturated fatty acid (PUFA) (> 1 double bond): eg. Omega 3, omega 6 Fatty acids: CH3C H CnOx - CH3 end is called the omega end.. the opposite end of the carboxylic acid end - omega 1, 2, 3 is counting the carbons from the omega end .. double bond appears after the carbon omega #.. named by FIRST appearance of double bond. for example: rd th th Omega 3: has the first double bond after the 3 .. but also has one after 6 and 9 Omega end  CH -CH -CH3=C -2H -.2 C(ωH)H -2(ω )H -C(1 )H3=CH-C2 2 3 2 2 The first carbon AFTER the carboxylic carbon is called the alpha carbon The next one over is called the beta carbon Beta oxidation (breaking up fatty acids for energy) – breaking occurs at the beta carbon Beta carbon and next carbon over become acetyl coA  important to react with oxaloacetate to form the citrate .. energy from ETC KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 111 Carboxylic acid reforms with the saturated end (other side of the beta part that breaks off) to keep the fatty acid formation in tact Beta oxidation.. 8 carbon goes to 6.. goes to 4.. goes to 2.. best use of it. Uses up all of it to produce acetyl coA’s for the krebs cycle omega 3’s are healthy, omega 6’s aren’t Examples: Oleic acid (18:1) – olive oil (thick) at room temperature, but may solidify with refrigeration, omega-9 FA Linoleic acid (18:2) – soybean oil, omega-6 and omega-9 fatty acids • Double bonds at 6 th and 9 thcarbons, respectively Linolenic acid (18:3) – flaxseed oil, very thin oil •Omega-3, -6, and –9 fatty acid, but by definition an omega 3 fatty acid high the number of unsaturated bonds, more fluid it is KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 112 Geometric shapes of fatty acids: Determined by the double bond Cis form (bent)….most common Trans form (straight), the more straight, the more solid at room temperature. Cis configuration – the H of the double bonds are on the same side - Causes a bent shape since the e’s in the H’s repel each other - Most food sources of fatty acids are the cis configuration Trans configuration – H of double bonds are on opposite sides of carbons - Linked to cardiovascular disease risk due to configuration - Found much less in natural food sources - Food processing referred to as hydrogenation (technique of adding hydrogens to unsaturated fatty acids) will produce trans fatty acids  reduces rancidity, makes it more solid ESSENTIAL AND NON-ESSENTIAL FATTY ACIDS Non-essential fatty acid: • Fatty acids our bodies can manufacture. • Carbons added to short-chain fatty acids by liver (elongation). • Done mainly for structural fatty acids (membranes and myelin) • Fatty acids in breast milk - Kids often require much greater proportion of fat than adults since they’re growing and nervous system is developing, adding new cells, which need membranes via lipids KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 113 Example: Oleic acid (omega-9)….body desaturates stearic acid. (18:0) Essential fatty acid: • No enzymes to desaturate before omega-9 carbon…..therefore, omega-3 and omega- 6 fatty acids are essential. Why do we need to ingest omega-3 and –6 fatty acids? • Used to make other fatty acids…called eicosanoids. Eicosanoids Regulates various physiological functions (>20 carbons) Manufactured in the liver Omega-3 fatty acids are beneficial to cardiovascular health Omega-3 fatty acid (Linolenic acid): • 18:3 • Canola, soybean, walnut, flaxseed oil Elongated (in liver) and desaturated to form 2 other FA’s: • Eicosapantaenoic acid (EPA) – 20:5 • Docosahexaenoic acid (DHA) – 22:6 • Going from 18:3 to 20:5 and 22:6… more carbons being added, greater degree of desaturation taking place • Essential fatty acids, food sources: fish (salmon, mackerel, flounder), shrimp o Particularly fatty fish, have these valuable omega 3’s and other essential fatty acids as well Physiological effects: •Promotes blood vessel dilation – getting wider, diameter increasing  indirectly decease BP, makes blood flow easier, heart can work less, decreases blood clotting, decreases inflammation.. considered to reduce CV disease risk … lipoproteins can cause inner lining of cardiovasc system to become inflamed – immune system activates WBC’s .. caused by ingested high fat foods and other things eg smoking KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 114 Omega-6 fatty acid: Linoleic acid (18:2) (omega 6) Arachidonic acid (20:4) (elongation and more double bonds)– precursor of prostaglandins (molecuels released by immune system in response to infection or inflammation) On a chronic level (eg tearing ankle).. inflammation response – secretion of prostaglandins to isolate injury to that place… BUT ingesting too much omega 6 may cause inflammation throughout CV system can lead to the following: Function: blood vessel constriction, promotes blood clotting, inflammation, thrombosis, platelet aggregation (blood clots), blood vessel size reduction Okay for injuries but bad if it happens in overall CV system. Makes pushing blood through CV system harder, increases blood pressure, left ventricle has to work much harder on a chronic basis. Foods high in lipids high in omega 6 leads to high BP leads to CV disease Food sources: cooking oils (sunflower, soybean, safflower), egg yolks, organ meats: liver- good source of fat soluble vitamins but huge source of omega 6’s and cholesterol, kidneys… Most of egg white is water and protein; egg yolk is the part with cholesterol and vitamins (fat soluble ones); egg white doesn`t do that Exercise is effective in managing high fat intake Omega-3 vs omega-6 fatty acids: North American diet: Over-balanced towards omega-6….10x needed amount of omega-6. Target ratio – 1:1 to 4:1 .. omega 6 to omega 3 (b/c omega 6 is much more abundant in food supply) Most food have more 6’s vs 3’s, but in terms of achieving optimal ratio.. that’s target.? Gamma-linoleic acid (omega-6 family) Ingested (usually) as a supplement and converted to dihomogamma linoleic acid (DGLA) In the presence of these micronutrients/minerals.. Magnesium, zinc, and vitamins C, B3, and B6…promotes conversion of GLA to DGLA, than AA (arachidonic acid) Supplements are designed to help promote conversion of omega 6`s to DGLA which is relatively harmless as opposed to AA since it`s the precursor for prostaglandins which leads to inflammation, thrombosis etc KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 115 Effect: negates/minimize pro-inflammatory effects of arachidonic acid Caution: history of seizures, pregnancy, certain medications Essential fat sources: Omega-3 FA: • α-linoleic: canola, olive oils, nuts (walnuts, peanuts, almonds – roasting destroys vitamins) • DHA, EPA: fish (Atlantic cod, haddock, salmon), human milk Omega-6 FA: • Linoleic acid: Plants, soybean and canola oils Omega-9 FA: Olive oil • Recommended ratio of omega-6 to omega-3 is 2:1 • Typical North American diet has much higher ratio (≈30:1) • Food processing contributes to increased ratio….omega-3’s are removed to reduce rancidity (prolong shelf life) .. omega 3’s have more unsaturated carbons.. so they remove that during partial hydrogenation .. adding more hydrogen atoms to saturate the fatty acids, makes them more solid at room temp Dietary fat sources: • Saturated fats: animal products, palm & coconut oils • Monounsaturated fats: nuts, olive, peanut, canola, safflower oils • PUFA: sunflower, corn, soybean oils • Trans-fat: Baked goods (also high in energy), fast foods, stick margarine KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 116 TRIGLYCERIDES FUNCTIONS: 1) Energy source: • Depends on physical activity level, glucose availability, blood insulin levels. • Infants: requires fat intake… development and growth of nervous system and cell membranes • Efficient at absorbing fats b/c we don’t need protein transporter, concentration gradient transport; passive. • In order to use fat as an energy substrate, we have to simultaneously combust glucose at the same time since glucose is a source of oxaloacetate which is combined with carbons from acetyl coA’s coming off fatty acids • Chronically high levels of insulin decreases body’s usage of fat for energy.. minimizes breakdown of adipocytes and promotes fat storage 2) Insulation/protection Visceral fat: protects visceral organs ( adipose tissue found around heart and internal organs; padding); much higher relation to development of CV disease because even though it’s stored in adipocytes, body still draws upon that fat for energy.. when those fatty acids are broken down, they enter CV system and fat molecules move through portal system of liver  accumulate in the liver and contribute to liver dysfunction more so than subcutanoues fat due to location of fat being near liver. Enter CV which is directed through the liver and impairs liver function.. sedentary lifestyle  fatty livers Subcutaneous fat: insulation barrier, reduces heat transfer.. Can we have too little fat?…..Yes. Anorexia nervosa: eating disorder, prolonged decrease in appetite and refusal to eat…..starvation. Too little fat will impair physiological processes.. cells constantly in a state of turnover and important characteristic are membranes, which cant be assembled without fat molecules. Less severe forms of energy imbalance: Amenorrhea: lack of menses.. exacerbated by high volume exercise (referred to as athletic induced amenorrhea) • Female athlete triad: amenorrhea, eating disorder, osteoporosis • Infertility problems in women KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 117 3) Improves bioavailability and transport of other fat-soluble nutrients • Vitamin A, D, E, K • Phytochemicals (carotenoids, lycopene)…..serving tomatoes with olive oil. o Enhances bioavailability, olive oil is high in triglycerides, improves absorption of these vitamins • To get vitamins ADEK Out of digestive into cardiovasc- have to be absorbed with dietary fat.. so bioavailability improves with other fat-soluble nutrients in meals 4) Flavour, texture, odour of foods • Sensory stimulation • Sometimes humans prefer texture over flavour • Moistens baked food items….also adds lots of energy…. energy content of a Tim Horton’s muffin? Over 400 calories b/c of fat included to moisten it • Used to add TiO2 (carcinogenic!) to skim milk .. whitening agent and thickening agent .. but gave it a blue tinge LOL. .. still used in sunscreen :o ironic. And many exercise supplements… FOOD PROCESSING OF FATS: Goal: Delay food “wasting”, improve palatability 1) Oxidation • Oxygen can bind to the double bond sites of PUFA’s….causes oxidative damage… becomes rancid (“bad odour”). • The more unsaturated, Solution: Add Vitamin E to food….is an anti-oxidant (added to oils). • Processing also removes phospholipids, phytochemicals and naturally occurring vitamin E. 2) Hydrogenation KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 118 • Hydrogen is added to double bonds….effect is to saturate a PUFA. Effect: • Solidifies the food product (margarine). • Protection from…..oxidation….so good, YES?….maybe not. • Hydrogenation is not a perfect process…..some of the double bonds get converted to…..trans-type. PHOSPHOLIPIDS: • Similar to triglycerides….contains glycerol and fatty acids. • Typically, one glycerol, 2 FA’s, and a phosphate (+ nitrogen)…makes the whole molecule hydrophobic and hydrophilic. • Glycerol is dissolvable in water / CV system and cells can take it up and convert it to a glycolytic intermediate.. halfway in glycolysis cycle, glycerol can be converted to one of those compounds and go through the rest of the cycle Functions: 1) Cell membrane structure • Provides fluidity, makes the membrane “functional”….hence the label “fluid mosaic model”. • Fatty acid component forming and breaking bonds with each other.. not just a hard shell.. allows things in and out b/c of fluiditiy 2) Lipid transport • Component of bile: assists with fat emulsification (occurs in small intestine) o Stored in gull bladder o Fat emulsification: Breaking down of triglycerides into fatty acids for absorption • Outer shell of chylomicrons and lipoproteins o Transport mechanism of lipids, cholesterol, and fat-soluble vitamins through the body (ADEK).. certain lipoproteins are healthy, certain ones aren’t KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 119 Food sources: • Egg yolks, soybeans, peanuts (not essential) • Not essential, body can produce its’ own phospholipids STEROLS: • Cholesterol • Ring structure, hydrophobic, lipophilic • Contains no fatty acid What is cholesterol? C 27O45 Why is cholesterol important? 1) Component of cell membranes (neurons) Too low cholesterol • Stroke, lung, liver and behavioural problems (emanate from CNS problems) • Decreased immunity • AIDS: decreasing cholesterol indicates disease worsening 2) Precursor of molecules (vitamin D and many hormones) • Vitamin D • Only get a component of UV rays so vitamin D synthesis abilities are lower due to NA location so milk is fortified with vitamin D KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 120 Hormones: Progestins: progesterone, healthy pregnancy Glucocorticoids: Cortisol – forms liver glycogen, fat and protein breakdown + Mineralocorticoids: aldosterone, Na reabsorption in kidney, blood pressure regulation Androgens: testosterone – male sex characteristics Estrogens: female sex characteristics Cells have ability to make cholesterol, therefore it`s not essential Food sources: animal food sources, none in plants; plant counterpart – phytosterols (healthy) Cholesterol synthesis: • All cells synthesize cholesterol • 1000 mg/day Example: Cells in eye lens – prevents cataracts Brain – synthesizes cholesterol during development Kids require a higher fat intake than adults due to development of nervous system but not the same thing for cholesterol since body can make it on its own, no increased need for kids to increase more cholesterol… DIFF than fats FOOD ITEMS • Animal origin ONLY for cholesterol • Plants contain phytosterols • Poorly absorbed, but….decreases absorption of cholesterol • Used as a cholesterol-reducing food ingredient • Plant sterols interfere with and inhibit absorption of animal cholesterol Cholesterol containing food items: Recommended daily value for cholesterol: <300 mg KIN 1F03 – Human Nutrition and Health D.M. Pincivero, 2012 121 Examples: 1 tbsp butter = 31 mg 1 large egg = 218 mg 3 oz beef = 90 mg 3 oz beef liver = 330 mg 3 oz beef brain = 1,420 mg With the exception of dairy, ingesting animal products do not provide carbs even though muscles are location of carb storage Organ meats… liver cells manufacture and store cholesterol .. don’t eat polar bear liver? Cholesterol absorption: • Lower bioavailability than FA because we need FA’s to absorb cholesterol.. cholesterol absorption increase with dietary lipids so if cholesterol is a problem, reduce the intake of animal based foods and reduce the intake of lipids since lipids increase c
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