CH 5 The Lipids Lipids include Fats l

CH 5: The Lipids

Lipids include…. Ø Fats l Butter, lard, margarine… Ø Oils l Plant oils - Corn oil, olive oil, peanut oil… Ø Cholesterol l Found in animal sources of fat • Dairy, egg yolk, butter, fatty meats. .

Functions of Fats in the Body Source of energy 2. Thermal insulation 3. Protect and supports organs 1. • Fats hold some organs in place Use to make all cells 5. Use to make important substances 4. • 6. E. g. sex hormones, bile, vitamin D…… Fatty foods contain fat soluble vitamins

Recommended Lipid Intake Ø 20 -35 % daily kcal from fats (TG) • Maximum 10% from saturated fats • Some say maximum 10% from polyunsaturated fats • Minimum 20% calories from fats • Limit intake of trans fats Ø Maximum 300 mg cholesterol per day • No or lower cholesterol intake is fine/good

Introduction to Lipids Ø Lipids – water insoluble component of cells l l Called hydrophobic Made of the elements: • • Carbon Hydrogen Oxygen Phosphorus (in phospholipids only)

Introduction to Lipids Classes of lipids: Fatty acids (FA) l • l May be saturated or unsaturated Triglycerides (TG) - the fats we eat • l Phospholipids • l 9 kcal/gram Also 9 kcal/gram Sterols • Not caloric

Fatty Acids Ø Fatty Acids - Long hydrocarbon chains with an acid head (pg 168) l Carbon chains differ in: • Length - most are 4 -24 carbons long • Number and type of double bonds

Fatty Acids Ø Saturated Fatty Acids l All carbon to carbon single bonds • Chain is saturated with hydrogens l Chain is relatively straight Ø Unsaturated Fatty Acids l At least one C to C double bond present • Called a “point of unsaturation” l Double bonds kink/bend the chain

Fatty Acids

Unsaturated Fatty Acids Ø Monousaturated FA (MUFA) l One C to C double bond Ø Polyunsaturated (PUFA) l More than one C to C double bond

Omega-3 and Omega-6 FA l l An omega-3 fatty acid - double bond starting on the 3 rd carbon from the “methyl end” (shown in green). An omega-6 fatty - double bond starting on the 6 th carbon from the “methyl end”.

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Cis and Trans Fatty Acids

Hydrogenation Reaction Ø Hydrogenation reaction adds hydrogens to double bonds to convert them to single bonds l TG may be partially or fully hydrogenated.

Hydrogenation Ø Partially hydrogenated TG l Some of double bonds saturated (made single bonds) • As a result oils become ______ l The remaining double bonds are converted from cis to trans form • Cis form is the naturally occurring form • Trans FA are associated with health risks

Hydrogenation Ø Fully hydrogenated TG l All double bonds are saturated • As a result oils become solids (stick margarine) l Converts an unsaturated oil to a saturated fat • Fully hydrogenated fats have the same health issues as natural sources of sat’d fats

Triglycerides Ø TG – chemical nature l l 3 carbon backbone (called glycerol) with 3 fatty acids (FA) attached (page 171) The chemical nature of the attached fatty acids determines the physical properties of the TG and its storage properties

TG Ø Back to TG - Glycerol with 3 FA attached Fatty Acid #1 Fatty Acid #2 Fatty Acid #3 l l l FA attached may differ Nature of FA impacts properties of the TG Page 170

Triglyceride

Saturated TG Ø TG with primarily saturated fatty acids attached l Solids at room temperature (fats) • Shorter the chain the softer the TG l l Primarily from animal sources More stable than TG w/ unsaturated FA • Store better l Saturated FA are associated w/ health risks

Saturated TG Sources Ø Food Sources Saturated Fats l l Butter, cream, milk, cheese Red meat Coconut and palm oil – plant sources of saturated fats Chicken - mixture of sat’d and unsat’d fats • Much of chicken fat is in the skin

Unsaturated TG Ø TG with primarily unsaturated FA l l l Liquids at room temperature (oils) Primarily from plant sources Double bonds are reactive • Therefore plant oils react with oxygen and go rancid easily

Unsaturated TG Sources Ø Sources of Unsaturated Fats l Monounsaturated • Olive oil, canola oil, peanut oil l Polyunsaturated • Corn oil, soybean oil, sunflower oil…. .

Essential Fatty Acids Ø 2 essential fatty acids l Omega-3 FA – linolenic acid • May lower cholesterol and risk of heart disease, hypertension, ? cancer, ? arthritis • Good food sources: fish, soy, nuts, many oils l Omega-6 FA – linoleic acid • Food sources are vegetable oils and poultry

© 2008 Thomson - Wadsworth

Fats in Foods Ø Review page 173

Phospholipids Ø Function: structural component of all cell membranes Ø Structure: l l Glycerol backbone (3 carbon) with 2 fatty acids attached and one phosphate group Attached to phosphate group is some other group

© 2008 Thomson - Wadsworth

Phospholipids Ø 9 kcal/gram Ø Don’t need to eat phospholipids • liver makes phospholipids for the body Ø Best known phospholipid is lecithin l Supplements are NOT needed • Can cause GI distress, loss of appetite

Phospholipids Ø Food sources: l l l Eggs yolk Liver and other organ meats Soybean Wheat germ Peanuts

Sterols Ø Structure: 4 linked carbon rings with side chains Ø Examples of sterols (we make in body) l l Cholesterol Vitamin D Bile salts Sex hormones

Cholesterol in Foods Ø See page 174 Ø Note all are animal sources Ø Leading sources of cholesterol in US diet l l Eggs (yolk) Beef products Dairy products – cheese, whole milk, ice cream Chicken

Overview Digestion & Absorption Ø Digest TG to: l Glycerol, fatty acids, and monoglycerides Ø Absorb: l l Glycerol and short chain FA (12 C or less) absorbed into capillaries liver Longer chain FA and monoglycerides first absorbed into SI cell, TG remade, then absorbed into lacteals (complicated process)

Digestion of Lipids - detail Ø Small amount of chemical digestion occurs in mouth and stomach l l Infants have an enzyme that begins digestion of TG found in milk – in mouth Adults make a small amount of gastric lipase • Begins digestion of TG in ______

Digestion of Lipids Ø Small Intestine l l Bile emulsifies fats (physical digestion) Pancreatic and SI lipases remove FA from TG and phospholipids • Digestion produces: • Fatty acids, glycerol, monoglycerides • Sterols do not need digestion

Absorption Ø Glycerol and short/medium chain FA, 12 C or less: l l Absorbed into the capillaries Go directly to the liver

Absorption Ø Long chain FA and monoglycerides l l l Form micelles Micelles are absorbed into SI cells In SI cells TG are remade! The newly made TG attach to protein carriers to form chlyomicrons – page 181 Chylomicrons are absorbed into lacteals

© 2008 Thomson - Wadsworth

Transport Ø Chylomicrons – lipoproteins l l l Primarily TG with protein carrier Travel through lymph and enter blood in chest Travel through the heart and then body • Enzymes break off fatty acids from TG and deliver them to cells for energy or storage as TG l Chylomicron remnants are then delivered to the liver

Transport In the liver – pages 181/182 l Liver breaks down remaining TG and remakes them! • Liver also makes cholesterol and other TG l These TG and cholesterol are packaged with proteins to make VLDL • Very low density lipoproteins – mostly TG

Transport Ø VLDL enters blood Ø VLDL delivers fatty acids to needy cells l l Density goes up as the fats leave the transport protein Relative amount of cholesterol goes up ad TG leave VLDL

Transport Ø VLDL becomes LDL as it loses FA l l l Low density lipoprotein LDL is high in cholesterol LDL circulates in blood delivering cholesterol to cells

Transport Ø LDL l l l “Bad” cholesterol Contributes to plaques when cholesterol “falls off” the LDL and is deposited on artery walls Plaques narrow arteries • Raises blood pressure • Increases risk of blood clots and heart attacks

Transport Ø HDL l l High density lipoprotein HDL transports cholesterol and other lipids back to liver for disposal • Can pick up cholesterol from plaques • Good cholesterol

Cholesterol Ø Maximum level of intake recommended l l 300 mg/day Make all we need, so no intake is fine Ø Food Sources – all animal (no plant sources) l l l Egg yolk Dairy (unless fat removed as in skim milk) Meat, poultry

Cholesterol Ø Blood levels l l Goal: total cholesterol < 200 mg/d. L (know this one) Other recommendations (do not need to know) • LDL < 100 mg/d. L • HDL > 60 mg/d. L • LDL: HDL ratio to be less than 5 for men and less than 4. 5 for women • Triglycerides < 150 mg/d. L

Lowering Cholesterol Levels Reduce intake of: 1. • • Saturated fats Trans fatty acids Cholesterol Sugars (if sugar sensitive) Increase intake of: 2. • • soluble fibers (oats and legumes) fish

Lowering Cholesterol Levels Moderate alcohol intake 4. Exercise – aerobic may be best 5. Lose weight 3. FYI - Estrogen lowers cholesterol levels Therefore, cholesterol levels often go up in postmenopausal women.

Weight Loss and Cholesterol Year 2003 2004 Weight 235 pounds 195 pounds Total cholesterol HDL 302 157 68 53 LDL 193 88 Triglycerides 206 97

Genetics Matter Male with a healthy weight and active lifestyle, but family history of heart disease Total chol. HDL Initial After Dietary values Changes 242 214 After Meds. 151 40 36 36 LDL 157 132 74 TG 223 230 203

Review Fat Sources Ø Saturated Fats Ø Monounsaturated Fats l olive, canola and peanut oil and avocados. Ø Polyunsaturated Fats l l vegetable oils (safflower, sesame, soy, corn and sunflower), nuts and seeds. Trans Fatty Acids Ø Cholesterol

Review Health Aspects Fats Ø Saturated Fats Ø Trans Fatty Acids Ø Cholesterol Ø Monounsaturated Fats Ø Polyunsaturated Fats

Health Effects and Recommended Intakes of Lipids Ø Health Effects of Lipids l Benefits from Omega-3 Fats • Beneficial effects in reducing risk of heart disease and stroke • Food sources include vegetable oils (canola, soybean and flaxseed), walnuts and flaxseeds, and fatty fish (mackerel, salmon, and sardines). l Need to avoid fish with high levels of mercury © 2008 Thomson - Wadsworth

Health Effects and Recommended Intakes of Lipids Ø Health Effects of Lipids l Balance Omega-6 and Omega-3 Intakes • Eat more fish (2 3 -oz. portions per week) and less meat. • Bake, broil or grill the fish. • Select healthy oils – in moderation • Supplements are not the answer. © 2008 Thomson - Wadsworth

© 2008 Thomson - Wadsworth

Review Ø Page 195