Lipids

1. Lipids Chapter 6

2. Learning Outcomes • Explain the basic chemical structure of fatty acids and how they are named • Describe the functions of triglycerides, fatty acids, phospholipids and sterols in the body • Classify and evaluate the different fatty acids based on their health benefits or consequences • Identify food sources of triglycerides, fatty acids, phospholipids and sterols

3. Learning Outcomes • Describe the recommended intake of lipids • Identify strategies for modifying total fat, saturated fat, and trans fatty acids intake • Explain the digestion, absorption and transport of lipids in the body • Discuss health concerns related to dietary fat intake • Describe dietary measures to reduce the risk of developing cardiovascular disease

4. Triglycerides • Most common lipid in food and the body • Make up 95% of what we eat and what is in our bodies • FA can all be the same or all be different, the fatty acids are long chains of carbons with hydrogensattached

5. Functions of Triglycerides • Provide energy • Provide compact energy source • Insulate and protect the body • Aid fat-soluble vitamin absorption and transport • Essential fatty acid functions

6. Food Sources of Triglycerides • Fruits and Vegetables • Low fat except avocados and coconuts • Dairy • Low fat products are available • Grains • Low-fat except when fat is added e.g. pastries, pancakes • Fats • Usually a combination of many-described by the predominate fat

7. Structure • Esterification • Joining 3 fatty acids to a glycerol unit • De-esterification • Release of fatty acids-results in free fatty acids • Diglyceride • Loss of one fatty acid • Monoglyceride • Loss of two fatty acids • Re-esterification • Reattaching a fatty acid to a glycerol that has lost a fatty acid

8. Carbon Chain Length • Long chain fatty acids • 12 or more carbons (ex. Beef, lamb, plant oils) • Medium chain fatty acids • 6-10 carbons (ex. coconut and palm oils) • Short chain fatty acids • Less than 6 carbons (ex. dairy products)

9. Saturation Each molecule wants to form as many bonds as it can • Carbon- 4 • Oxygen- 2 • Hydrogen-1

10. Saturation • Saturated fatty acids • This 18 carbon fatty acid is fully saturated with hydrogen atoms. • No double bonds • Increase blood levels of cholesterol • Example: red meat, high fat dairy, coconut and palm oil- solid at room temperature.

11. Saturation • Monounsaturated fatty acids • One double bond • Decrease blood levels of cholesterol • Example: olive oil, canola oil, peanut oil

12. Saturation • Polyunsaturated fatty acids • Many double bonds (at least 2) • Decrease blood levels of cholesterol • Example: Vegetable oils and fish oil

13. Shape • Cis fatty acids • Bent carbon chain • Trans fatty acids • Straight carbon chain • Hydrogenation: Adding hydrogen to make an unsaturated fat more saturated-yields: trans fatty acids • Solidifies the lipid, increases shelf life of product (tub margarine, baked goods) • Increases cholesterol even more than saturated fat

14. Trans Fats

15. Trans Fats 1902- Scientist Wilhelm Normann finds that liquid oils can be hydrogenated to form trans fatty acids.  1911- Procter & Gamble introduces Crisco vegetable shortening in grocery stores.  1937- As World War II progresses, the use of margarine (yellow colored vegetable shortening) rises sharply due to butter rationing. 1984- Consumer advocacy groups campaign against using saturated fat for frying in fast-food restaurants. In response, most fast-food companies begin using partially hydrogenated oils containing trans fat instead of beef tallow and tropical oils high in saturated fats.

16. Trans Fats 1990s there were several studies correlating trans fatty acids and increased LDL (bad) cholesterol levels and a higher incidence of heart disease.  1993- Health advocacy groups call for fast-food restaurants to stop using partially hydrogenated oils in their deep fryers. 1999- The U.S. government proposes a law requiring food manufacturers to list trans fat amounts on nutrition labels.  The proposal is not passed as law.

17. Trans Fats 2002- The government agrees with researchers for the first time on record: that there is likely no safe level of trans fat and that people should eat as little as possible. 2003- The FDA passes a law requiring that trans fat be listed on the Nutrition Facts label on food products; food manufacturers have three years to comply.  2006- Trans fat labeling becomes mandatory in the United States. 

18. Should trans fats be legal? Illegal • Denmark, 2003 • Banned in almost all foods • Heart disease has fallen by 20% between 2001 (before the ban) and 2006 (two years after the ban) • NY City, 2006 • Restaurants/food service establishments • Switzerland, 2008 • Banned in almost all foods Legal or limited • Some restrict the amount of trans fat in foods (Canada, Boston) • Others mandate labeling • Others have no laws concerning trans fat

19. Trans Fat Labeling Loophole Any food that contains 0.5 grams or less of trans fat can be listed as zero grams on the Nutrition Facts label. It may seem like a small amount, but there is no safe amount and all those half grams can add up. You must read the ingredients label: “partially hydrogenated” is in the list, it is a food that contains trans fats and should be avoided.

20. Naming fatty acids(Omega and Delta) • Omega System • Double bond closest to omega (methyl) end • Omega-3 fatty acid is 18:3 ω3 • Omega-6 is 18:2 ω6

21. Omega 6 and omega 3 fatty acids Eicosanoid “Local hormone”

22. Two Essential Fatty Acids Alpha-linolenic(Omega-3) • Polyunsaturated • Major source of Omega 3 fatty acids in foods • Used to make EPA and DHA and Eicosanoids Linoleic (Omega-6) • Polyunsaturated • Major source of Omega 6 fatty acids in foods • Used to make Arachidonic acid, and Eicosanoids

23. Two Essential Fatty Acids • Alpha-linolenic • Cold water fish (salmon, tuna, sardines), walnuts, flax, canola oil • Reduces inflammation, thins blood, and reduces plasma triglycerides • Linoleic • Beef, poultry, safflower oil, sunflower oil, corn oil, mayonnaise • Regulates blood pressure, can increase blood clotting and inflammation

24. Essential Fatty Acid Needs • Body unable to synthesize so Adequate Intake has been established • Approximately 2-4 Tablespoons daily • Omega 6 intake usually high, Omega 3 intake usually too low-this in balance has health consequences • Deficiency • Unlikely • Could result in slowed growth, flaky and dry skin, delayed wound healing • Toxicity • No upper level set

25. 32 mg DHA 500 mg as ALA AHA 1000mg of DHA + EPA = 2 servings of fish/week Alpha linolenic acid ALA (flax, mayo), lower cholesterol but no relationship w/heart disease and may increase risk of prostrate cancer 3000 mg of DHA+EPA in 6oz 3 soft gels=900mg of DHA + EPA

26. Dietary Fats

27. Dietary Fat Recommendations

28. American Heart Association Recommendations • Limit saturated fats to 10% of total calories • Limit polyunsaturated fats to 10% of total calories • Minimize trans fat intake • Limit cholesterol intake to less than 300 mg • Eat at least two servings of fatty fish/week (tuna, salmon, mackerel, lake trout, herring, and sardines)

29. Fat Intake • North American fat intake has doubled in the last century • Too high • Saturated fat, trans fat, Omega 6 • Too low • Omega 3

30. Mediterranean Diet • Up to 40% fat if comprised of monounsaturated fatty acids • Diet is high in • Olive oil, fruits, vegetables, whole grains, beans, nuts and seeds • Small to moderate amounts of cheese, yogurt and fish • Limit eggs and red meat • Exercise

31. Mediterranean Diet • Breakfast: Greek yogurt topped with berries and walnuts; Coffee or teaLunch: Lentil soup with swish chard topped with taziki sauce; hummus and pitaSnack: Whole grain crackers and cheeseDinner: Roasted cod paired with a wheat berry salad consisting of olive oil vinaigrette, feta, parsley, and tomatoes and a glass of red wineDessert: Fresh fruit drizzled with honey

32. Fat Replacements • Water, Protein, Air (soft serve ice cream) • Carbohydrates • Fiber (Ztrim) • Corn syrups, syrup solids, and high-fructose corn syrups are used as fat replacers in many fat-free and reduced-fat cookies • Engineered fats • Olestra (Lays's Light, Ruffles Light, Doritos Light, and Tostitos Light)

33. Olestra • Olestra is synthesized from sucrose, it can bond with six, seven, or eight fatty acids, making it too large and irregular to move through the intestinal wall and be absorbed. • Because olestra is undigested, it inhibits absorption of fat soluble vitamins (fun side effects of this!) • FDA requires manufacturers to add vitamins A, D, E and K to products made with olestra to counter that effect.

34. Phospholipids • Hydrophobic and Hydrophilic Ends • Functions • Component of cell membranes • Emulsifier • Sources • Synthesized by the body • Food: lecithin in egg yolks, wheat germ and peanuts

35. Phospholipids

36. Sterols • Ring structure, most known is cholesterol • Plant sterols block cholesterol absorption sites in the human intestine, thus helping to reduce cholesterol in humans, but there is some concern that they may block absorption of other important nutrients as well • Functions • Steroid hormones, bile, cell membranes, chylomicrons • Sources • Synthesized by the body • Food: animal origin (meat, fish, eggs, dairy) • Food additive: Benecol and Take Control

37. Sterols needed to make steroid hormones

38. Fat Digestion • Stomach • Gastric lipase • Triglycerides are broken down into monoglycerides and free fatty acids • Liver-makes bile • Gall bladder • CCK triggers bile release from gall bladder • Pancreas • Pancreatic lipase, phospholipase, cholesterol lipase into common bile duct, which empties to SI

39. Fat Digestion • Small Intestine • Bile emulsifies fat to form micelles (acted upon by pancreatic lipase) • Phospholipids are broken down into free fatty acids, glycerol and phosphoric acid by enzymes from the SI and pancreas • Cholesterol esters are broken down into cholesterol and free fatty acids by enzymes from SI and pancreas • Most digestion in duodenum and ileum

40. Fat Digestion Bile emulsifies fat: breaks it into tiny droplets called micelles (keeps the fat suspended in the water-based intestinal contents

41. Fat absorption

42. Fat absorption • The lipid portion of micelles is absorbed by the brush border of the absorptive cells in the duodenum and jejunum • Short and medium chain fatty acids are absorbed via the portal vein • Long chain fatty acids are re-esterified and enter the lymphatic system • Bile is recycled via enterohepatic circulation

43. Transporting Fat • Transporting fat through water based blood and lymphatic system is a challenge • Short and medium chain fatty acids travel via cardiovascular system to liver • Long chain enter lymph system • Fat is transported lipoproteins • Lipid core • Shell composed of protein, phospholipid and cholesterol that allow transportation

44. Types of Lipoproteins • Chylomicrons • Transport of dietary triglycerides from small intestine to cells • VLDL • Carries mainly triglycerides from liver to cells • LDL • Made mostly of cholesterol, carries cholesterol to cells • HDL • Made mostly of protein, pick up and recycle or dispose of cholesterol

45. Types of Lipoproteins

46. Pathways for Cholesterol Uptake • Receptor Pathway • LDL is removed from blood by cells via the LDL receptor • In cells the LDL is broken down and utilized in the body (to do what?) • Excess builds up and becomes oxidized

47. Pathways for Cholesterol Uptake High Density Lipoproteins (HDL or good cholesterol) • How does it get its name? • Picks up cholesterol throughout the body-eventually this leads to excretion of LDL • Blocks oxidation of LDL “Scavenger” WBC embed in blood vessels and engulf and digest LDL • Can build up over time-plague develops (what is this called?)

48. Atherosclerosis • What can you do to prevent plaque buildup? • What do cholesterol lowering medications do? • How can you remove an existing plaque to prevent heart attack and stroke?

49. Cardiovascular Disease (CVD) • Development of CVD • Atherosclerotic plaque forms • Result: Heart attack and stroke • Risk factors • Cannot change age, gender, race and genetics • Can change blood triglyceride and cholesterol levels, hypertension, smoking, physical inactivity, obesity, diabetes and other diseases

50. Blood Lipoprotein levels