DNT 200 NUTRITION FOR HEALTH SCIENCES

1. DNT 200NUTRITION FOR HEALTH SCIENCES LIPIDS

2. DNT 200NUTRITION FOR HEALTH SCIENCES Everything I want is either illegal, immoral, or fattening Alexander Woollcott American Writer, 1887 - 1943

3. LIPIDS DEFINITION Lipids are a family of compounds that include triglycerides (fats and oils), phospholipids (e.g. lecithin), and sterols (e.g. cholesterol)

4. LIPIDS TRIGLYCERIDES Are the chief form of fat in the diet and the major storage form of fat in the body • Over 90% of the fats we eat are triglycerides • Are composed of three fatty acids attached to glycerol • Can be simple (where the three fatty acids are the same) or mixed (where at least one of the fatty acids are different)

5. LIPIDS TRIGLYCERIDES Glycerol -- An organic alcohol composed of a three carbon chain with a hydroxyl group on each of its three carbons Hydroxyl Group

6. LIPIDS Methyl Group Acid Group TRIGLYCERIDES Fatty Acid -- an organic compound composed of a carbon chain with hydrogens attached; has an acid group at one end and a methyl group at the other end

7. LIPIDS TRIGLYCERIDES A Mixed Triglyceride

8. LIPIDS FATTY ACIDS Differ from one another by: • Chain length • Affects the way the fat is absorbed • Short (less than 6 carbons) and medium (6-10 carbons) chain fatty acids are absorbed directly into the blood • Long chain fatty acids are made into triglycerides in the intestinal cells, assembled into chylomicrons which are transported through the lymphatic system to the blood

9. LIPIDS FATTY ACIDS Differ from one another by: • Degree of saturation • A saturated fatty acid’s chain is filled to capacity with hydrogen • A monounsaturated fatty acid contains one double bond • A polyunsaturated fatty acid contains more than one double bond

10. LIPIDS FATTY ACIDS Differ from one another by: • Degree of saturation Saturated and unsaturated fatty acids

11. LIPIDS FATTY ACIDS • Whether a fat is soft or hard depends on which fatty acids are incorporated into it • Fats with shorter fatty acids are softer and melt more readily • Humans as well as animals can synthesize fatty acids • Within limits the type of fat eaten will determine the types of triglycerides made • Saturated fats tend to raise blood cholesterol; monounsaturated and polyunsaturated fats tend to lower blood cholesterol

12. LIPIDS FATTY ACIDS Hydrogenation Hydrogenation -- a chemical process by which hydrogens are added to unsaturated or polyunsaturated fats to reduce the number of double bonds making them more saturated (solid) and more resistant to oxidation (rancidity)

13. LIPIDS FATTY ACIDS Configuration Cis Bonds • Hydrogens on either side of the double bond on the carbon chain are either both “up” or both “down” such that both are on the same side of the molecule • Are typical of the configuration in natural foods (except in milk and butter, which contain trans bonds)

14. LIPIDS FATTY ACIDS Configuration Trans Bonds • Hydrogens are on opposite sides of the double bond, that is one “up” and one “down” across from each other • Are not essential • Provide no known health benefit • Their safety is questioned • Trans fatty acids raise LDL and lower HDL at least to the same extent that saturated fatty acids do • Trans fatty acids may be carcinogenic • Are now seen to be more damaging than saturated fats • Will have to be listed on labels by 2005

15. LIPIDS FATTY ACIDS Configuration Cis and trans bonds

16. LIPIDS FATTY ACIDS Configuration Trans Bonds (continued) • Are more stable than cis bonds • During hydrogenation, some of hydrogen atoms shift around some double bonds, changing them to trans bonds • Using oil for frying causes some of the cis bonds to convert to trans bonds -- if the oil is constantly re-used more of the cis bonds are changed to trans until significant numbers of fatty acids with trans bonds build up

17. LIPIDS FATTY ACIDS Configuration

18. LIPIDS FATTY ACIDS Special Cases Omega 3 Fatty Acids • First double bond is three carbons from the methyl end of the fatty acid • Abundant in plant and fish oils • Deficiencies unlikely but may lead to neurological and visual problems • Primary representative is Linolenic Acid • Beneficial in lowering blood cholesterol and preventing heart disease

19. LIPIDS FATTY ACIDS Special Cases Linolenic Acid • An essential fatty acid with 18 carbons and three double bonds (humans cannot synthesize) • Is a polyunsaturated fatty acid

20. LIPIDS FATTY ACIDS Special Cases Linolenic Acid • Abundant in fats and oils (canola, soybean, walnut, wheat germ, margarine and shortening made from canola and soybean oil), nuts and seeds, and soybeans Linolenic Acid

21. LIPIDS Dietary Reference Intake Value Linolenic Acid AI • Males over 14 -- 1.6 grams • Females over 14 -- 1.1 grams (except pregnant and lactating) 2002 Data

22. LIPIDS FATTY ACIDS Special Cases Omega 6 Fatty Acids • First double bond is six carbons from the methyl end of the fatty acid

23. LIPIDS FATTY ACIDS Special Cases Omega 6 Fatty Acids • Abundant in meats and seeds of plants (and the oils produced by these seeds) • Important in stimulating skin and hair growth, regulating metabolism, promoting the transport of fatty acids from the liver to the tissues, and maintaining reproductive performance -- also implicating cancer development in some animals • Primary representative is Linoleic Acid

24. LIPIDS FATTY ACIDS Special Cases Linoleic Acid • An essential fatty acid with 18 carbons and two double bonds (humans cannot synthesize) • Is a polyunsaturated fatty acid • Common in vegetable oils

25. LIPIDS FATTY ACIDS Special Cases Linoleic Acid Linoleic Acid

26. LIPIDS Dietary Reference Intake Value Linoleic Acid AI • Males 19 - 50 -- 17 grams • Females 19 - 50 -- 12 grams (except pregnant and lactating • Males over 50 -- 14 grams • Females over 50 -- 11 grams 2002 Data

27. LIPIDSComparison of Dietary Fats

28. LIPIDS PHOSPHOLIPIDS Phospholipids -- Compounds similar to triglycerides but with choline (a B-Vitamin) (or similar compound) and a phosphorus containing acid in place of one of the fatty acids • Most have a backbone of glycerol • Contains nitrogen as well as phosphorus • Together with sterols, make up only 5% of the lipids in the diet • Are soluble in both water and fat

29. LIPIDS PHOSPHOLIPIDS • Functions • Are major parts of cell membranes • Act as emulsifying agents (keeps other fats in solution in the blood and body fluids) • Can be made by the body -- not essential • Example -- lecithin (an emulsifier found in egg yolks and soybeans)

30. LIPIDS Phosphate Group PHOSPHOLIPIDS Lecithin Choline

31. LIPIDS STEROLS Sterols -- A compound composed of carbon, hydrogen, and oxygen atoms arranged in rings like those of cholesterol with any of a variety of side chains attached • Can be made by the body in the liver -- raw material comes from glucose or saturated fatty acids • Examples -- Cholesterol, Vitamin D, Testosterone (sex hormone)

32. LIPIDS STEROLS Cholesterol

33. LIPIDS STEROLS Cholesterol • Is the “most famous” sterol • Performs structural and metabolic functions in the cells • Made in the liver • After manufacture • May be made into bile • May be deposited in the body’s cells • May accumulate in the arteries

34. LIPIDS STEROLS Cholesterol (continued) Cholesterol Transport • Cholesterol leaves the liver packaged with other lipids and protein -- called lipoproteins • Blood carries lipoproteins through all of the arteries • Tissues can extract the lipids from the lipoproteins • To pass into the cells, lipids must first pass the artery walls -- some are deposited there

35. LIPIDS

36. LIPIDS LIPID TRANSPORT Within the circulatory system there are four main types of lipoproteins • Chylomicrons • Made in the intestines • Are the largest and least dense (with the highest percentage of protein and lowest percentage of fat) of the lipoproteins • Function -- Transport diet-derived fat lipids (mostly triglycerides) from the intestine to the rest of the body • Cells all over the body remove lipids from the chylomicrons as they pass by so they get smaller and smaller

37. LIPIDS LIPID TRANSPORT Chylomicrons

38. LIPIDS LIPID TRANSPORT • Very Low Density Lipoproteins (VLDL) • Similar to Chylomicrons but made by different tissues -- made primarily by the liver cells • Function -- deliver triglycerides to the body’s cells (composed primarily of triglycerides) • As they loose triglycerides, the VLDL gather cholesterol from other lipoproteins circulating in the bloodstream and eventually become Low Density Lipoproteins (LDL)

39. LIPIDS LIPID TRANSPORT • Low Density Lipoproteins (LDL) • Made in the liver as VLDL as cells remove triglycerides from them • Composed primarily of cholesterol • Function -- deliver cholesterol to the body’s cells • LDL circulates through the body making their contents available to all the cells • Special LDL receptors in the liver remove LDL from circulation

40. LIPIDS LIPID TRANSPORT • High Density Lipoproteins (HDL) • The type of lipoprotein made by the liver and small intestine • Function -- pick up excess cholesterol and phospholipids from the body’s cells and take it back to the liver (‘reverse’ cholesterol transport) • Composed of protein and lipid

41. LIPIDS LIPID TRANSPORT

42. LIPIDS

43. LIPIDS LIPID TRANSPORT

44. LIPIDS LIPID TRANSPORT Other Routes For Cholesterol Besides being transported in lipoproteins, it can also be transformed into bile by the liver and stored in the gall bladder • May then be used to emulsify fat and be re-absorbed • May be trapped by dietary fiber and be excreted

45. LIPIDS LIPID METABOLISM Storing Fat as Fat • Most cells depend on the special cells of the adipose tissues to take up and store fat • Lipoprotein lipase (LPL) extracts triglycerides from passing lipoproteins, hydrolyze them, and and pass the components into the cells’ interiors -- there they are re-assembled into triglycerides • Adipose cells store fat after meals when a heavy traffic of chylomicrons and VLDL loaded with triglycerides pass by

46. LIPIDS LIPID METABOLISM Using Fat As Energy • When cells demand energy, hormone-sensitive lipase inside the adipose cells responds by dismantling stored triglycerides and releasing the breakdown products (glycerol and fatty acids) directly into the blood • In the last steps of breakdown, each fat fragment combines with a fragment from the breakdown of glucose before being completely oxidized to carbon dioxide and water • The body’s fat stores have virtually unlimited capacity • Fat supplies approximately 60% of the body’s on-going energy needs during rest -- during exercise, an even greater contribution is made

47. LIPIDS FAT IN FOODS Functions • Provides flavor and aroma • Vitamins A, D, E, and K are soluble in fat • Provides source of energy (9 Calories per gram) • Provides thermal insulation • Waterproofing external surfaces of both plants and animals • Protects vital organs (padding)

48. LIPIDS FAT IN FOODS Reducing dietary fat is widely recommended • Eliminate fat as a seasoning and in cooking • Cut down on intake of red meat • Remove the fat from high fat foods • Substitute high fat foods with specially manufactured lower fat versions of those foods • Replace high fat foods with natural low fat alternatives

49. LIPIDS FAT IN FOODS

50. LIPIDS FAT IN FOODS Health Effects of Fats • Many diseases are linked to excess body fat or excessive intakes of dietary fat • Obesity • Diabetes • Hypertension • Atherosclerosis (when the arteries that carry blood to the heart are blocked)