Lipids include…. • Fats • Butter, lard, margarine… • Oils • Plant oils - Corn oil, olive oil, peanut oil… • Cholesterol • Found in animal sources of fat • Dairy, egg yolk, butter, fatty meats..
Recommended Lipid Intake • 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 • Maximum 300 mg cholesterol per day • No or lower cholesterol intake is fine/good
Introduction to Lipids • Lipids – water insoluble component of cells • Called hydrophobic • Made of the elements: • Carbon • Hydrogen • Oxygen • Phosphorus (in phospholipids only)
Introduction to Lipids Classes of lipids: • Fatty acids (FA) • May be saturated or unsaturated • Triglycerides (TG) - the fats we eat • 9 kcal/gram • Phospholipids • Also 9 kcal/gram • Sterols • Not caloric
Fatty Acids • Fatty Acids - Long hydrocarbon chains with an acid head (pg 168) • Carbon chains differ in: • Length - most are 4-24 carbons long • Number and type of double bonds
Fatty Acids • Saturated Fatty Acids • All carbon to carbon single bonds • Chain is saturated with hydrogens • Chain is relatively straight • Unsaturated Fatty Acids • At least one C to C double bond present • Called a “point of unsaturation” • Double bonds kink/bend the chain
Unsaturated Fatty Acids • Monousaturated FA (MUFA) • One C to C double bond • Polyunsaturated (PUFA) • More than one C to C double bond
Omega-3 and Omega-6 FA • An omega-3 fatty acid - double bond starting on the 3rd carbon from the “methyl end” (shown in green). • An omega-6 fatty - double bond starting on the 6th carbon from the “methyl end”.
Hydrogenation Reaction • Hydrogenation reaction adds hydrogens to double bonds to convert them to single bonds • TG may be partially or fully hydrogenated.
Hydrogenation • Partially hydrogenated TG • Some of double bonds saturated (made single bonds) • As a result oils become ___________ • 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 • Fully hydrogenated TG • All double bonds are saturated • As a result oils become solids (stick margarine) • Converts an unsaturated oil to a saturated fat • Fully 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) • 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 • Nature of FA impacts properties of the TG • Page 170 Fatty Acid #1 Fatty Acid #2 Fatty Acid #3
Saturated TG • TG with primarily saturated fatty acids attached • Solids at room temperature (fats) • Shorter the chain the softer the TG • Primarily from animal sources • More stable than TG w/ unsaturated FA • Store better • Saturated FA are associated w/ health risks
Saturated TG Sources • Food Sources Saturated Fats • Butter, cream, milk, cheese • Red meat • Coconut and palm oil – plant sources of saturated fats • Chicken - mixture of sat’d and unsat’dfats • Much of chicken fat is in the skin
Unsaturated TG • TG with primarily unsaturated FA • 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 • Sources of Unsaturated Fats • Monounsaturated • Olive oil, canola oil, peanut oil • Polyunsaturated • Corn oil, soybean oil, sunflower oil…..
Essential Fatty Acids • 2 essential fatty acids • Omega-3 FA – linolenic acid • May lower cholesterol and risk of heart disease, hypertension, ?cancer, ?arthritis • Good food sources: fish, soy, nuts, many oils • Omega-6 FA – linoleic acid • Food sources are vegetable oils and poultry
Phospholipids • Function: structural component of all cell membranes • Structure: • Glycerol backbone (3 carbon) with 2 fatty acids attached and one phosphate group • Attached to phosphate group is some other group
Phospholipids • 9 kcal/gram • Best known phospholipid is lecithin • Supplements are NOT needed • Can cause GI distress, loss of appetite • Liver makes phospholipids for the body
Phospholipids • Food sources: • Eggs (yolk only) • Liver • Soybean • Wheat germ • Peanuts
Sterols • Structure: 4 linked carbon rings with side chains • Examples of sterols (we make in body) • Cholesterol • Vitamin D • Bile salts • Sex hormones
Digestion of Lipids • Digest TG to: • Glycerol, fatty acids, and monoglycerides • Absorb: • Glycerol and short chain FA into capillaries • Longer chain FA and monoglycerides into lacteals (complicated process)
Digestion of Lipids • Small amount of chemical digestion occurs in mouth and stomach • 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 • Small Intestine • 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 • Glycerol and short/medium chain FA • Absorbed into the capillaries • Go directly to the liver
Absorption • Long chain FA and monoglycerides • 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 157 • Chylomicrons are absorbed into lacteals
Transport • Chylomicrons – lipoproteins • 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 • Chylomicron remnants are then delivered to the liver
Transport In the liver • Liver breaks down remaining TG and remakes them! • Liver also makes cholesterol and other TG • These TG and cholesterol are packaged with proteins to make VLDL • Very low density lipoproteins
Transport • VLDL enters blood • VLDL delivers cholesterol and fatty acids to needy cells • Density goes up as the fats leave the transport protein
Transport • VLDL becomes LDL as it loses FA • Low density lipoprotein • LDL is high in cholesterol • LDL circulates in blood delivering cholesterol to cells
Transport • LDL • “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 • HDL • High density lipoprotein • HDL transports cholesterol and other lipids back to liver for disposal • Can pick up cholesterol from plaques • Good cholesterol
Cholesterol • Maximum level of intake recommended • 300 mg/day • Make all we need, so no intake is fine • Food Sources – all animal (no plant sources) • Egg yolk • Dairy (unless fat removed as in skim milk) • Meat, poultry
Cholesterol • Blood levels • Goal: total cholesterol < 200 mg/dL (know this one) • Other recommendations (do not need to know) • LDL < 100 mg/dL • HDL > 60 mg/dL • LDL:HDL ratio to be less than 5 for men and less than 4.5 for women • Triglycerides < 150 mg/dL
Lowering Cholesterol Levels • Reduce intake of: • Saturated fats • Trans fatty acids • Cholesterol • Sugars (if sugar sensitive) • Increase intake of: • soluble fibers (oats and legumes) • fish
Lowering Cholesterol Levels • Moderate alcohol intake • Exercise – aerobic may be best • Lose weight FYI - Estrogen lowers cholesterol levels Therefore, cholesterol levels often go up in postmenopausal women.
Genetics MatterMale with a healthy weight and active lifestyle, but family history of heart disease
Functions of Fats in the Body • Source of energy • Thermal insulation • Protect and supports organs • Fats hold some organs in place • Use to make all cells • Use to make important substances • E.g. sex hormones, bile……
Review Fat Sources • Saturated Fats • Monounsaturated Fats • olive, canola and peanut oil and avocados. • Polyunsaturated Fats • vegetable oils (safflower, sesame, soy, corn and sunflower), nuts and seeds. • Trans Fatty Acids • Cholesterol
Review Health Aspects Fats • Saturated Fats • Trans Fatty Acids • Cholesterol • Monounsaturated Fats • Polyunsaturated Fats