THE LIPIDS TRIGLYCERIDES PHOSPHOLIPIDS STEROLS 1 Lipids A

THE LIPIDS: TRIGLYCERIDES, PHOSPHOLIPIDS, & STEROLS 1

Lipids ü A family of compounds that includes triglycerides (fats and oils), phospholipids, and sterols. ü Fats- lipids in foods or the body, both of which are composed mostly of triglycerides. ü Oils- liquid fats at room temperature. 2

Triglycerides ü The chief form of fat in the diet and the major storage form of fat in the body ü Composed of a glycerol backbone with three fatty acids attached ü The most common triglyceride is the 18 carbon stearic acid. 3

Fatty Acids ü Fatty acid- an organic compound composed of a carbon chain with hydrogens attached an acid alcohol group (COOH) at one end. ü Saturated FA- a fatty acid carrying the maximum number of hydrogen atoms. ü Unsaturated FA- a fatty acid that lacks hydrogen atoms and has at least one double bond between carbons. 4

MUFAs And PUFAs ü Monounsaturated FA- a fatty acid that lacks two hydrogen atoms and has one double bond between carbons. ü Polyusaturated FA- a fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons. 5

Health Effects Of PUFAs And MUFAs ü PUFAs lower LDL or “bad” cholesterol. . ü Some research suggests that MUFAs increase HDL or “good” cholesterol while other research suggests that PUFAs and MUFAs lower both LDL and HDL cholesterol. ü PUFAs should replace saturated fats in the diet. 6

Food Sources Of PUFAs & MUFAs PUFAs üSafflower oil üSunflower oil üCorn oil üSoybean oil üCottonseed oil MUFAs üOlive oil üCanola oil üPeanut oil 7

Essential Fatty Acids ü A fatty acid needed by the body but not made in amounts sufficient to meet physiological needs. The human body makes all its fatty acids with the exception of linoleic and linolenic acid. 8

Omega 3 & 6 Fatty Acids ü Omega- the last letter of the Greek alphabet, used by chemist to refer to the position of the first double bond from the methyl end. ü Linoleic acid- primary member of the omega-6 family in which the first double bond is six carbons from the methyl end of the carbon chain. ü Linolenic acid- primary member of the omega-3 family in which the first double bond is 3 carbons away from the methyl end. 9

Health Effects Of Essential Fatty Acids ü May play an important role in the prevention and treatment of heart disease, hypertension, arthritis, and cancer. 10

Food Sources Of Essential Fatty Acids Omega-6 ü Leafy vegetables ü Seeds ü Nuts ü Grains ü Meats ü Vegetable oils Omega-3 ü Nuts ü Seeds ü Wheat germ ü Shellfish ü Fish ü Vegetable oils 11

Hydrogenation And Trans. Fatty Acids ü Hydrogenation- a chemical process by which hydrogens are added to unsaturated fats to reduce the number of double bonds, making the fat more saturated and resistant to oxidation. ü Trans-fatty acids- fatty acids with an unusual configuration around the double bond. They occur as a result from the process of hydrogenation. 12

Health Effects Of Trans-Fatty Acids ü Trans-fatty acids alter blood cholesterol the same way saturated fats do. ü There is a link between trans-fatty acids and heart disease. ü Margarine versus butter? 13

Phospholipids ü A compound similar to a triglyceride but having a phosphate group (phosphorus containing salt) and choline (nitrogen-containing group) in place of one of the fatty acids ü Found in foods such as eggs, liver, soybeans, wheat germ, and peanuts ü Important constituents of cell membranes 14

Sterols ü Compounds composed of carbon, hydrogen, and oxygen molecules arranged in rings, with any variety of side chains attached. ü The most famous sterol is cholesterol. 15

Role Of Sterols serve as important compounds in the body. Sterols include: ü Bile acids ü Sex hormones ü Adrenal hormones 16

Cholesterol ü Cholesterol is made endogenously (in the body). ü Exogenous cholesterol from our diet is consumed only from animal sources such as meat, eggs, fish, poultry and dairy products. ü Endo = within ü Exo = outside (the body) 17

Digestion Of Lipids ü Fats are hydrophobic or water-fearing. ü In the mouth- the salivary glands release lipase which plays a small role in the start of digestion. ü In the stomach- fat floats as a layer above the other components of food, as a result little digestion takes place here. 18

Digestion Of Lipids {continued} ü In the small intestines- when fat arrives in the duodenum, the gall bladder receives a signal to release bile from storage. ü The hormone cholecystokinin (CCK) is what triggers the gallbladder to release bile. ü Bile emulsifies the fat. ü Pancreatic lipases are released as well as some intestinal lipases. 19

Absorption Of Lipids ü Small molecules of glycerol, medium and short chain fatty acids diffuse easily into the intestinal cells and are absorbed directly into the bloodstream. ü Larger molecules, the monoglycerides and long chain fatty acids form micelles. ü Micelles- tiny spherical complexes that arise during fat digestion carrying fatty acids and monoglycerides into the cells. 20

Absorption of Lipids {continued} ü Once inside the cells, the fatty acids and monoglycerides form new triglycerides. ü The new triglycerides, along with cholesterol and phospho- lipids, form into transport vehicles called chylomicrons. ü The chylomicrons are released into the lymphatic system by the intestinal cells. ü The chylomicrons travel through the lymph to the 21 blood stream.

Transport Of Lipids ü Lipoproteins- clusters of lipids associated with protein that serve as transport vehicles for lipids in the lymph and blood. ü Chylomicrons- the class of lipoproteins that transport lipids from the intestinal cells into the body. ü VLDL- very low density lipoprotein, the type of lipoprotein made primarily by the liver to transport lipids to tissues of the body; Composed mainly of triglycerides. 22

Transport Of Lipids {continued} ü LDL- low density lipoprotein, the type of lipoprotein derived from VLDLs as cells remove triglycerides from them; Mainly composed of cholesterol. Known as “bad” cholesterol because elevated levels lead to heart disease. ü HDL- high density lipoprotein, the type of lipoprotein that transports cholesterol back to the liver from the cells; Composed mainly of protein. Known as “good” cholesterol because optimal levels decrease the risk of heart disease. 23

Lipids In The Body ü Triglycerides are stored in the adipose cells. ü Unfortunately the body’s storage is unlimited. ü Lipids provide more than twice the energy of carbohydrates. 24

Fats In Foods ü The degree of unsaturation of fats affects health. ü The degree of unsaturation influences firmness at room temperature. ü Butter is more solid than margarine as it contains more saturated fat. ü Vegetable oils are liquid at room temperature due to their large proportions of unsaturated fat. 25

Recommended Intakes Of Fat ü Total fat should account for 30% or less of total energy intake daily. ü Saturated fat should account for no more than 10% of total energy intake. ü Dietary cholesterol should not exceed 300 milligrams daily. 26

Avoid The “Hidden Fats” ü Salad dressings ü Tuna, egg, potato, pasta salads ü Meats marbled with fats ü Foods such as olives, avocados, and nuts 27