1. Chap. 5: Lipids

2. FAT FACTS  Lipids or “Fats” are essential to good health  Fat is found in almost all foods  Recommended intake of dietary fat: 20%-35% of kcal. 20%-35% of kcal.  3,500 kcal = 1 lb. of fat

3. Properties of Lipids  Do  Do not readily dissolve in water  Fats  Fats are solid at room temperature  Oils  Oils are liquid at room temperature  Triglycerides  Triglycerides are the main form of lipids in food and body (storage)  Energy  Energy dense (9 kcal /gm)

4. Functions of Somatic Fat  Stored Energy Reserve  Insulation  Cushioning  Transport fat-soluble vitamins  Forms Cell Membranes (cholesterol)

5. Functions of Dietary Lipids  Concentrated source of energy (kcal)  Satiety (slows emptying of stomach)  Aroma, Flavor and mouth feel

6. Requirements for Dietary Fat  20% to 35% of total caloric intake.  This is approximately 44 to 77 grams of fat if you consume 2000 kcal per day.  Less than 10% of the daily kcal intake should be from saturated fat.  This is approximately 22 grams of saturated fat if you consume 2000 kcal/day.  A large percentage of fat intake should come from monounsaturated oils.

7. Sources of Dietary Lipids

8. Types of Fat  Triglycerides Make up 95% of all fats Make up 95% of all fats Composed of a water soluble glycerol and three water insoluble fatty acids Composed of a water soluble glycerol and three water insoluble fatty acids  Phospholipids Composed of glycerol, 2 fatty acids and a phosphorus. Composed of glycerol, 2 fatty acids and a phosphorus. Primary function is to emulsify fats. Primary function is to emulsify fats.  Sterols Compounds composed of several carbon rings that has several biological functions Compounds composed of several carbon rings that has several biological functions

9. Triglycerides  The most common type of fat found in the body (95% of all fats are triglycerides)

10. Triglycerides H H--C--OH H--C--OH H--C--OH H Fatty Acid + H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H Fatty Acid Condensation

11. Fatty Acid Structure (Fig. 5-1-A) omega endalpha end Methyl endAcid end H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

12. Saturated Fatty Acid Structure (Fig. 5-1-A) omega endalpha end Note: All carbons connected by single bonds Note: All carbons connected by single bonds H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

13. Monounsaturated Fatty Acid Structure (Fig. 5-1-B) omega endalpha end Note: Only ONE double bond Note: Only ONE double bond H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

14. Polyunsaturated Fatty Acid Structure (Fig. 5-1-C) omega endalpha end > 2 double bonds > 2 double bonds H H H H H H H H H H H H H O H-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

15. Triglycerides can contain a mixture of saturated, monounsaturated and polyunsaturated fatty acids. Most of our dietary lipids are mixed triglycerides.

17. Characteristics of Fatty Acids  Saturated fatty acids are solid at room temperature and are resistant to oxidation. Should be consumed sparingly in diet.  Monounsaturated Fats are liquid at room temperature. Rate of oxidation: low. Consumption does not have to be limited.  Polyunsaturated Fats are liquid at room temperature. Rate of oxidation: High. Should be consumed moderately.

18. Oxidation  Oxidation: The removal of electron(s) from atoms of a compound or element by oxygen or another ion/atom.  Alters appearance or function of compound or element  EX: Rust on iron

19. Fat Oxidation Concerns  Fatty acid oxidation in the body increases free radical production which destroys cells  Fatty acid oxidation in the body damages arterial walls and increases CVD risk  Fatty acid oxidation in foods is not harmful, but is unpleasant to taste and smell. Oil that is oxidized is called “rancid.”

20. Hydrogenation of Fatty Acids  Process used to solidify an oil and slow oxidation.  Addition of H to C=C double bonds  Increases shelf life  Formation of trans fatty acid (similar to shape of saturated fatty acid)

21. Cis and Trans Fatty Acid

22. Health Dangers of Excessive Trans Fatty Acid  Raises LDL  Lowers HDL  Increases risk for heart disease  Damages artery walls

23. Minimize Intake of Trans Fatty Acid  Limit use of solid oils (margarine)  Limit deep-fried foods  Limit high fat baked goods  Limit use of all processed foods

24. Essential Fatty Acids  Needed  Needed for production of hormone- like compounds called eicosanoids which regulate inflammation, clotting, immune function, vision, and allergic response.

25.  Essential Fatty Acids Omega 6 Omega-3 Linoleic acid Alpha-linolenic acid (corn, soybeans, nuts, seeds, greens) (canola oil, walnuts, flaxseed) Gamma-Linolenic acid DHA (borage oil, primrose oil) (docosahexanoic acid) Fish oil Arachidonic Acid EPA (meat) (eicosapentaenoic acid) Fish oil

26. The Different Effects  Omega-6 increases increases blood clotting inflammatory responses promotes promotes activation of leukocytes  Omega-3 reduces reduces heart attack Inhibits Inhibits inflammation cancer growth decreases decreases blood clotting excess excess may cause hemorrhagic stroke Ratio of Omega 6: Omega 3 4:1

27. Essential Fatty Acid- Omega-6 (alpha- linoleic acid) omega endalpha end 1st double bond is located on the 6th carbon from the omega end 1st double bond is located on the 6th carbon from the omega end H H H H H H H H H H H H H O H-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H H H H H H H

28. Omega-6 Fatty Acid  Found in vegetable oils  Only need ~ 1 tablespoon a day  About 14g per day

29. Essential Fatty Acid- Omega-3 (alpha- linolenic acid) omega endalpha end 1st double bond is located on the 3rd carbon from the omega end 1st double bond is located on the 3rd carbon from the omega end H H H H H H H H H H H H H H H H H O H-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OH H H H H H H H H H H H

30. Omega-3 Fatty Acid  EPA and DHA Primarily from fish oil, Omega 3 eggs.  Alpha-Linolenic found in canola oil, soybean oil, flaxseed oil, enriched cereals, and walnuts  Recommend intake of ~2 servings of fish per week or 6-10 oz.  About 2 grams per day.

31. Phospholipid  Built on a glycerol backbone  Has at least one fatty acid replaced with phosphorus compound  Found in body  Synthesized by the body as needed

32. Functions of Phospholipids  Make up cell membrane  Emulsifier Bile acids Bile acids Lecithins Lecithins Improves food products Improves food products

33. Emulsifier Hydrophilic end (attracts water) Hydrophilic end (attracts water) Hydrophobic end (attracts lipid) Hydrophobic end (attracts lipid)

34. Emulsification

35. Sterols: Cholesterol  Essential component of cell membrane  Produced by the liver  Found only in animal products  Forms important hormones Estrogen, testosterone, vitamin D Estrogen, testosterone, vitamin D  Precursor to bile acids

36. Structure of Cholesterol

37. Dietary Cholesterol  Dietary cholesterol is found only in animal products. Since the liver makes cholesterol, only things with a liver have cholesterol.  Dietary cholesterol serves no purpose since the liver makes all your body needs.  Dietary cholesterol has little affect on blood cholesterol.

38. LIPID DIGESTION

39. Digestion of Fat in the Stomach  Gastric  Gastric lipase lipase works only in an acidic environment  Gastric  Gastric lipase acts on triglycerides containing short & medium chain fatty acid  Longer  Longer fatty acid chain is not affected by the stomach

40. Digestion of Fat in the Small Intestine  Primary site of fat digestion  CCK stimulates pancreas to release pancreatic lipase  Pancreas release lipase  Bile acid emulsifies digested fat  Fat is broken down to monoglycerides and fatty acids

41. Absorption of Lipids  Diffuse into the absorptive cells  Short and medium chain (<12 C) fatty acids are water soluble Enters the blood stream, sent to liver via the portal vein Enters the blood stream, sent to liver via the portal vein  Long chain fatty acids reforms into Triglycerides for special transport via the lymphatic system.

42. Carrying Lipids in the Bloodstream  Triglycerides  Triglycerides are too large to be transported in the blood.  Unique  Unique system of fat transportation is needed called “lipoproteins.”  Lipoproteins  Lipoproteins are packaged lipids with a protein exterior and are transported to the bloodstream via lymph.

43. Lipoproteins

44. Types of Lipoproteins  Chylomicrons. Largest of the lipoproteins carry mostly triglycerides from the intestines to the rest of the body via lymph.  VLDL. Very low density lipoproteins. Carry mostly chylomicron remnants and lipids assembled by the liver.  LDL. Low density lipoprotein. The remnant of VLDL. Carries mostly cholesterol. Has a propensity to oxidize and damage arteries  HDL. High density lipoprotein. Carries some lipids, but is mostly protein. Retrieves cholesterol from the cells and delivers to the liver for recycling.

46. Dangers of too much fat  Obesity Diabetes Diabetes Hypertension Hypertension cancer cancer  Elevated Triglycerides and Cholesterol Diabetes Diabetes Heart disease Heart disease