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Lipids Lipids Do not readily dissolve in water Types of lipids: – Triglycerides – Phospholipids – Sterols (Cholesterol) Fats (solid) and oils (liquid) – 9 kcal /gm Chemical Forms of Common Lipids Fatty Acids Found in our body and foods – In triglycerides Saturated fatty acids – Solid form Unsaturated fatty acids – Liquid form Fats are composed of both saturated and unsaturated fatty acids Fatty Acid Structure H H H H H H H H H H H H H H H HHO 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 omega end Degree of saturation alpha end Saturated Fatty Acid Structure H H H H H H H H H H H H H H H HHO 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 omega end alpha end Degree of saturation: single carbon bond Monounsaturated Fatty Acid Structure 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 omega end alpha end One double bond Polyunsaturated Fatty Acid Structure H H H H H H H H H H H HH 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 omega end alpha end > 2 double bonds Composition of Common Fats / Oils Essential Fatty Acids Omega-3 fatty acid (alpha-linolenic acid) Omega-6 fatty acid (linoleic acid) Body can only make double bonds after the 9th carbon from the omega end Functions – Immune function, vision, cell membrane, and production of hormone-like compounds Triglycerides Most common form of fats and oils in our body & in the foods we eat Fatty acids attached to a glycerol Triglycerides Glycerol + 3 FA’s Triglyceride + 3 H20 Phospholipids Built on a glycerol backbone Contains phosphorus compound(s) Found in body Synthesized by the body as needed Functions of Phospholipids Component of cell membrane Emulsifier – Bile acids – Lecithins – Improves food products Found in wheat germ, peanuts, yolks, soy beans, organ meat Sterols Multi-ringed structure Do not have a glycerol backbone Cholesterol is a sterol Waxy substance Do not readily dissolve in water Found in animal foods Lipids in Foods Hidden Fat Look on the Nutrition Facts labels Look on the lists of ingredients Control portion size Reduced-Fat Foods Calorie content is about the same Sugar is commonly added in place of fat Fat Substitutes Water – Diet margarine Z-trim – Starch derivative that binds with water Fiber cellulose – Maltrin, Stellar, Oatrim Dairy-Lo – Protein globules Olestra or Olean (links fatty acid to sucrose) – Not digested – FDA approved for fried snack foods – Fat-soluble vitamins issue Hydrogenation of Fatty Acids Process used to solidify an oil Addition of H to C=C double bonds Increases shelf life Formation of trans fatty acid – (similar to shape of saturated fatty acid) Excessive Trans Fatty Acid Intake Raises LDL Lowers HDL Increases risk for cardiovascular disease Current intake is 3%-4% of total kcal Added to food labels Jan. ‘06 Typical Sources of Trans Fat Minimize Intake of Trans Fat Limit use of hydrogenated fats Limit deep-fried foods Limit high-fat baked goods Limit use of non-dairy creamers Absorption of Fat 95% of dietary fat is absorbed Diffused into the absorptive cells Short- and medium-chain (<12 C) fatty acids – Are water soluble – Enter the portal system Long-chain fatty acids re-form into triglycerides – Not water soluble – Enter the lymphatic system Carrying Fat in the Bloodstream Water (blood) and oil (fat) are incompatible Unique system of fat transportation is needed Transportation of Absorbed Fatty Acids Re-formed into triglycerides Packaged into chylomicrons Lipoprotein lipase – Breaks down triglycerides in the chylomicrons Chylomicron remnant – Delivered to the liver Lipoproteins Composition and Roles of Lipoproteins Transportation of Synthesized Fat Made primarily by the liver Very-Low-Density Lipoprotein (VLDL) Low-Density Lipoprotein (LDL) High-Density Lipoprotein (HDL) Functions of Essential Fatty Acids Essential Fatty Acid- Omega-3 (alpha-linolenic acid) H H H H H H H H H H H H H H H HH 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 omega end alpha end 1st double bond is located on the 3rd carbon from the omega end Omega-3 Fatty Acid Primarily from fish oil Also found in canola, walnuts, flax seeds, mussels, crab, shrimp, and soybean oil Recommended intake of ~2 servings of fish per week Essential Fatty Acid- Omega-6 (alpha-linoleic acid) 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 omega end alpha end 1st double bond is located on the 6th carbon from the omega end Omega-6 Fatty Acid Found in vegetable oils Only need ~ 2-4 tablespoons a day Health-related Effects Archidonic acid (Omega-6 ) – Increases blood clotting – Increases inflammatory responses DHA, EPA (Omega-3) – Decrease blood clotting – Reduce heart attack – Decrease inflammation – Excess may cause hemorrhagic stroke – Other possible uses: Lower triglycerides, rheumatoid arthritis, behavioral disorders Signs and Symptoms of Essential Fatty Acids Deficiency Flaky, itchy skin Diarrhea Infections Retarded growth and wound healing Functions of Fatty Acids Provide energy Efficient storage of energy Insulation Protection Transport fat-soluble vitamins Some satiety Flavor and mouth feel Recommendations for Fat Intake No RDA AHA recommendations – 20-30% of total kcal from fat – 7-10% can come from saturated/trans fat – 200-300 mg cholesterol/day Average U.S. intake: – 33% of total kcal from fat – 13% of kcal from saturated fat – 180-320 mg cholesterol/day AHA Goals AHA Recommendations Other Recommendations Fat intake can be higher as long as saturated and trans fatty acid are minimal Eat plenty of fruits and vegetables Cut down on red meats Cut down on simple sugars and refined carbohydrate Promote healthy weight Be active Cutting the Fat