Lipids

Lipids Do not readily dissolve in water Do not readily dissolve in water Types of lipids: Types of lipids: –Triglycerides –Phospholipids –Sterols (Cholesterol) Fats (solid) and oils (liquid) Fats (solid) and oils (liquid) –9 kcal /gm

Chemical Forms of Common Lipids

Fatty Acids Found in our body and foods Found in our body and foods –In triglycerides Saturated fatty acids Saturated fatty acids –Solid form Unsaturated fatty acids Unsaturated fatty acids –Liquid form Fats are composed of both saturated and unsaturated fatty acids Fats are composed of both saturated and unsaturated fatty acids

Fatty Acid Structure omega endalpha end Degree of saturation Degree of saturation 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

Saturated Fatty Acid Structure omega endalpha end Degree of saturation: single carbon bond Degree of saturation: single carbon bond 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

Monounsaturated Fatty Acid Structure omega endalpha end One double bond 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

Polyunsaturated Fatty Acid Structure 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

Composition of Common Fats / Oils

Essential Fatty Acids Omega-3 fatty acid (alpha-linolenic acid) Omega-3 fatty acid (alpha-linolenic acid) Omega-6 fatty acid (linoleic acid) Omega-6 fatty acid (linoleic acid) Body can only make double bonds after the 9th carbon from the omega end Body can only make double bonds after the 9th carbon from the omega end Functions 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 Most common form of fats and oils in our body & in the foods we eat Fatty acids attached to a glycerol Fatty acids attached to a glycerol

Triglycerides Glycerol + 3 FA’s Triglyceride + 3 H H 2 0

Phospholipids Built on a glycerol backbone Built on a glycerol backbone Contains phosphorus compound(s) Contains phosphorus compound(s) Found in body Found in body Synthesized by the body as needed Synthesized by the body as needed

Functions of Phospholipids Component of cell membrane Component of cell membrane Emulsifier Emulsifier –Bile acids –Lecithins –Improves food products Found in wheat germ, peanuts, yolks, soy beans, organ meat Found in wheat germ, peanuts, yolks, soy beans, organ meat

Sterols Multi-ringed structure Multi-ringed structure Do not have a glycerol backbone Do not have a glycerol backbone Cholesterol is a sterol Cholesterol is a sterol Waxy substance Waxy substance Do not readily dissolve in water Do not readily dissolve in water Found in animal foods Found in animal foods

Functions of Cholesterol Essential component of cell membrane Essential component of cell membrane Produced by the liver Produced by the liver Found only in animal products Found only in animal products Forms important hormones Forms important hormones –Estrogen, testosterone, vitamin D Precursor to bile acids Precursor to bile acids

Lipids in Foods

Emulsifiers

Hidden Fat Look on the Nutrition Facts labels Look on the Nutrition Facts labels Look on the lists of ingredients Look on the lists of ingredients Control portion size Control portion size

Reduced-Fat Foods Calorie content is about the same Calorie content is about the same Sugar is commonly added in place of fat Sugar is commonly added in place of fat

Fat Substitutes Water Water –Diet margarine Z-trim Z-trim –Starch derivative that binds with water Fiber cellulose Fiber cellulose –Maltrin, Stellar, Oatrim Dairy-Lo Dairy-Lo –Protein globules Olestra or Olean (links fatty acid to sucrose) Olestra or Olean (links fatty acid to sucrose) –Not digested –FDA approved for fried snack foods –Fat-soluble vitamins issue

Rancidity Decomposed oils Decomposed oils Breakdown of the C=C bonds by UV light, and/or O 2 Breakdown of the C=C bonds by UV light, and/or O 2 Unpleasant odor and flavor Unpleasant odor and flavor PUFA more susceptible PUFA more susceptible Limited shelf life Limited shelf life

Prevention of Rancidity Hydrogenation Hydrogenation Addition of vitamin E Addition of vitamin E Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT) Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT)

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

Hydrogenation

Cis and Trans Fatty Acid

Excessive Trans Fatty Acid Intake Raises LDL Raises LDL Lowers HDL Lowers HDL Increases risk for cardiovascular disease Increases risk for cardiovascular disease Current intake is 3%-4% of total kcal Current intake is 3%-4% of total kcal Added to food labels Jan. ‘06 Added to food labels Jan. ‘06

Typical Sources of Trans Fat

Minimize Intake of Trans Fat Limit use of hydrogenated fats Limit use of hydrogenated fats Limit deep-fried foods Limit deep-fried foods Limit high-fat baked goods Limit high-fat baked goods Limit use of non-dairy creamers Limit use of non-dairy creamers

Digestion of Fats and Oils

Digestion of Fat in the Stomach Gastric lipase Gastric lipase –Activated by an acidic environment –Acts on triglycerides containing short- and medium-chain fatty acids

Digestion of Fat in the Small Intestine Primary site of fat digestion Primary site of fat digestion Hormone Cholecystokinin (CCK) Hormone Cholecystokinin (CCK) –Stimulates release of pancreatic lipase Bile acid released Bile acid released –Emulsifies digested fat Fat is broken down Fat is broken down –To monoglycerides and fatty acids

Absorption of Fat 95% of dietary fat is absorbed 95% of dietary fat is absorbed Diffused into the absorptive cells Diffused into the absorptive cells Short- and medium-chain (<12 C) fatty acids Short- and medium-chain (<12 C) fatty acids –Are water soluble –Enter the portal system Long-chain fatty acids re-form into triglycerides 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 Water (blood) and oil (fat) are incompatible Unique system of fat transportation is needed Unique system of fat transportation is needed

Transportation of Absorbed Fatty Acids Re-formed into triglycerides Re-formed into triglycerides Packaged into chylomicrons Packaged into chylomicrons Lipoprotein lipase Lipoprotein lipase –Breaks down triglycerides in the chylomicrons Chylomicron remnant Chylomicron remnant –Delivered to the liver

Lipoproteins

Composition and Roles of Lipoproteins

Transportation of Synthesized Fat Made primarily by the liver Made primarily by the liver Very-Low-Density Lipoprotein (VLDL) Very-Low-Density Lipoprotein (VLDL) Low-Density Lipoprotein (LDL) Low-Density Lipoprotein (LDL) High-Density Lipoprotein (HDL) High-Density Lipoprotein (HDL)

High-Density Lipoprotein (HDL) Synthesized by liver and intestine Synthesized by liver and intestine High proportion of protein High proportion of protein Picks up cholesterol from dying cells and other sources Picks up cholesterol from dying cells and other sources Transfers cholesterol to other lipoproteins Transfers cholesterol to other lipoproteins Transfers cholesterol directly back to the liver Transfers cholesterol directly back to the liver

Benefits of (a high) HDL (level) Removes cholesterol from the bloodstream Removes cholesterol from the bloodstream HDL may block oxidation of LDL HDL may block oxidation of LDL Reduces risk of cardiovascular disease Reduces risk of cardiovascular disease Pre-menopausal women have higher HDL Pre-menopausal women have higher HDL

Scavenger WBC removes (oxidized) LDL from circulation Scavenger WBC removes (oxidized) LDL from circulation Build-up of plaque on walls of the blood vessels Build-up of plaque on walls of the blood vessels Development of atherosclerosis Development of atherosclerosis Vessel damage caused by: Vessel damage caused by: –Smoking, diabetes, hypertension, homocysteine, high LDL, infection Scavenger Cells

Antioxidant Reduces oxidation Reduces oxidation Slows LDL uptake by scavenger cells Slows LDL uptake by scavenger cells

Functions of Essential Fatty Acids

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

Omega-3 Fatty Acid Primarily from fish oil Primarily from fish oil Also found in canola, walnuts, flax seeds, mussels, crab, shrimp, and soybean oil Also found in canola, walnuts, flax seeds, mussels, crab, shrimp, and soybean oil Recommended intake of ~2 servings of fish per week Recommended intake of ~2 servings of fish per week

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

Omega-6 Fatty Acid Found in vegetable oils Found in vegetable oils Only need ~ 2-4 tablespoons a day Only need ~ 2-4 tablespoons a day

Health-related Effects Archidonic acid (Omega-6 ) Archidonic acid (Omega-6 ) –Increases blood clotting –Increases inflammatory responses DHA, EPA (Omega-3) 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 Flaky, itchy skin Diarrhea Diarrhea Infections Infections Retarded growth and wound healing Retarded growth and wound healing

Functions of Fatty Acids Provide energy Provide energy Efficient storage of energy Efficient storage of energy Insulation Insulation Protection Protection Transport fat-soluble vitamins Transport fat-soluble vitamins Some satiety Some satiety Flavor and mouth feel Flavor and mouth feel

Recommendations for Fat Intake No RDA No RDA AHA recommendations AHA recommendations –20-30% of total kcal from fat –7-10% can come from saturated/trans fat – mg cholesterol/day Average U.S. intake: Average U.S. intake: –33% of total kcal from fat –13% of kcal from saturated fat – mg cholesterol/day

AHA Goals

AHA Recommendations

Advice from National Cholesterol Education Program and Food and Nutrition Board Up to 35% of total kcal from fat Up to 35% of total kcal from fat Keep saturated fat, cholesterol, and trans fat to a minimum Keep saturated fat, cholesterol, and trans fat to a minimum

Other Recommendations Fat intake can be higher as long as saturated and trans fatty acid are minimal Fat intake can be higher as long as saturated and trans fatty acid are minimal Eat plenty of fruits and vegetables Eat plenty of fruits and vegetables Cut down on red meats Cut down on red meats Cut down on simple sugars and refined carbohydrate Cut down on simple sugars and refined carbohydrate Promote healthy weight Promote healthy weight Be active Be active

Cutting the Fat

Road to a Heart Attack

Cardiovascular Disease Myocardial infarction Myocardial infarction Cerebrovascular disease Cerebrovascular disease

Risk Factors Total blood cholesterol > 200 mg/dl Total blood cholesterol > 200 mg/dl Smoking Smoking –Increases clotting –Increases expression of genetic link Hypertension (> 139/89) Hypertension (> 139/89) Diabetes Diabetes –Insulin increases cholesterol synthesis –Guarantees development of cardiovascular disease

Other Risk Factors Low HDL (< 40 mg/dl) Low HDL (< 40 mg/dl) Age Age Family history Family history Blood triglycerides > 200 mg/dl Blood triglycerides > 200 mg/dl Obesity Obesity –Fat around the waist –Insulin resistance Inactivity Inactivity

Signs of a Heart Attack Intense, prolong chest pain Intense, prolong chest pain Shortness of breath Shortness of breath Sweating Sweating Nausea and vomiting Nausea and vomiting Dizziness Dizziness Weakness Weakness Jaw, neck, shoulder pain Jaw, neck, shoulder pain Irregular heartbeat Irregular heartbeat

Medical Intervention For those who experience a heart attack For those who experience a heart attack –Or have CVD or diabetes ndex/htm ndex/htm ndex/htm ndex/htm Medication to lower LDL Medication to lower LDL –Reduce cholesterol synthesis (Statins, “Lipitor”) –Binds to bile acids for elimination Medication to lower blood triglycerides Medication to lower blood triglycerides –Reduce triglyceride synthesis

Lowering LDL See your doctor to assess for other conditions See your doctor to assess for other conditions Reduce dietary saturated fat and cholesterol Reduce dietary saturated fat and cholesterol Increase MUFA and PUFA Increase MUFA and PUFA Increase dietary fiber (soluble) Increase dietary fiber (soluble)

Lowering Blood TG Is the most diet-responsive blood lipid Is the most diet-responsive blood lipid Avoid overeating Avoid overeating Limit alcohol Limit alcohol Limit simple sugars Limit simple sugars Small frequent meals Small frequent meals Include fish in the diet Include fish in the diet

Other Possible Methods Benecol and Take Control margarines Benecol and Take Control margarines –Plant stanol/sterol esters –Cholesterol-lowering effects –Decrease absorption of cholesterol and lower amount returning via enterohepatic circulation –Liver takes up more cholesterol from the blood

Raising HDL Physical activity Physical activity At least 45 min/day, 4 days a week At least 45 min/day, 4 days a week Don’t smoke Don’t smoke Eat regularly Eat regularly Eat less total fat Eat less total fat Moderate intake of alcohol increases HDL Moderate intake of alcohol increases HDL