CH 5: The Lipids

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

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

Recommended Lipid Intake  % daily kcal from fats (TG) Maximum 10% from saturated fatsMaximum 10% from saturated fats Some say maximum 10% from polyunsaturated fatsSome say maximum 10% from polyunsaturated fats Minimum 20% calories from fatsMinimum 20% calories from fats Limit intake of trans fatsLimit intake of trans fats  Maximum 300 mg cholesterol per day No or lower cholesterol intake is fine/goodNo or lower cholesterol intake is fine/good

Introduction to Lipids  Lipids – water insoluble component of cells Called hydrophobic Called hydrophobic Made of the elements: Made of the elements: CarbonCarbon HydrogenHydrogen OxygenOxygen Phosphorus (in phospholipids only)Phosphorus (in phospholipids only)

Introduction to Lipids Classes of lipids: Fatty acids (FA) Fatty acids (FA) May be saturated or unsaturatedMay be saturated or unsaturated Triglycerides (TG) - the fats we eat Triglycerides (TG) - the fats we eat 9 kcal/gram9 kcal/gram Phospholipids Phospholipids Also 9 kcal/gramAlso 9 kcal/gram Sterols Sterols Not caloricNot caloric

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

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

Fatty Acids

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

Omega-3 and Omega-6 FA An omega-3 fatty acid - double bond starting on the 3 rd carbon from the “methyl end” (shown in green). 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”. 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  Hydrogenation reaction adds hydrogens to double bonds to convert them to single bonds TG may be partially or fully hydrogenated. TG may be partially or fully hydrogenated.

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

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

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

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

Triglyceride

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

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

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

Unsaturated TG Sources  Sources of Unsaturated Fats Monounsaturated Monounsaturated Olive oil, canola oil, peanut oilOlive oil, canola oil, peanut oil Polyunsaturated Polyunsaturated Corn oil, soybean oil, sunflower oil…..Corn oil, soybean oil, sunflower oil…..

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

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Fats in Foods  Review page 173

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Transport  HDL High density lipoprotein High density lipoprotein HDL transports cholesterol and other lipids back to liver for disposal HDL transports cholesterol and other lipids back to liver for disposal Can pick up cholesterol from plaquesCan pick up cholesterol from plaques Good cholesterolGood cholesterol

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

Cholesterol  Blood levels Goal: total cholesterol < 200 mg/dL (know this one) Goal: total cholesterol < 200 mg/dL (know this one) Other recommendations (do not need to know) Other recommendations (do not need to know) LDL < 100 mg/dLLDL < 100 mg/dL HDL > 60 mg/dLHDL > 60 mg/dL LDL:HDL ratio to be less than 5 for men and less than 4.5 for womenLDL:HDL ratio to be less than 5 for men and less than 4.5 for women Triglycerides < 150 mg/dLTriglycerides < 150 mg/dL

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

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

Weight Loss and Cholesterol Year Weight 235 pounds 195 pounds Total cholesterol HDL6853 LDL19388 Triglycerides20697

Genetics Matter Male with a healthy weight and active lifestyle, but family history of heart disease Initial values After Dietary After Changes Meds. Total chol HDL LDL TG

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

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

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

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

© 2008 Thomson - Wadsworth