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Chap. 5: Lipids Properties of Lipids Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature Triglycerides are the main form of lipids in food and body (storage) Unsaturated Fatty Acids Saturated Fatty Acids Essential Fatty Acids Energy dense (9 kcal /gm) Fatty Acid Structure (Fig. 5-1-A) omega end degree of saturation alpha end Saturated Fatty Acid Structure (Fig. 5-1-A) omega end alpha end degree of saturation: single carbon bond Monounsaturated Fatty Acid Structure omega end alpha end One double bond Polyunsaturated Fatty Acid Structure omega end (Fig. 5-1-B) > 2 double bonds (Fig. 5-1-C) alpha end Essential Fatty Acids Body can only make double bonds after the 9th carbon from the omega end Needed for immune function, vision, cell membrane, and production of hormone-like compounds Essential Fatty Acid- Omega-3 (alpha-linolenic acid) 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 or soybean oil Recommend intake of ~2 servings of fish per week Essential Fatty Acid- Omega-6 (alpha-linoleic acid) 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 tablespoon a day ~1 Essential Fatty Acids The Different Effects Archidonic acid (Omega-6 ) increase blood cot increase inflammatory responses DHA, EPA (Omega-3) decrease blood clotting reduces heart attack excess may cause hemorrhagic stroke large amounts may decrease inflammation pain with rheumatoid arthritis Signs and Symptoms of Essential Fatty Acids Deficiency Flaky, itchy skin Diarrhea Infections Retarded growth and wound healing Anemia Triglycerides Glycerol + 3 FA’s Triglyceride + 3 H 20 (Ester bond) Triglycerides esterification desterfication 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 Functions of Phospholipids Make up cell membrane Emulsifier Bile acids Lecithins Improves food products Emulsifier Hydrophilic end (attracts water) Hydrophobic end (attracts lipid) Emulsification Cholesterol A multi-ringed structure Do not have a glycerol backbone Waxy substance Do not readily dissolve in water Cholesterol is a sterol Functions of Cholesterol Essential component of cell membrane Produced by the liver Found only in animal products Forms important hormones Estrogen, testosterone, vitamin D Precursor to bile acids Lipids in Foods Hidden Fat Look on the Nutrition Facts Look on the lists of ingredients Control portion size Reduce-Fat Foods Total energy 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 (links fatty acid to sucrose) not digested fat-soluble vitamins issue Digestion of Fat in the Stomach Gastric lipase works only in an acidic environment Gastric lipase acts on triglycerides containing short & medium chain fatty acid Longer fatty acid chain is not affected by the stomach 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 Absorption of Fat Diffuse into the absorptive cells Short and medium chain (<12 C) fatty acids are water soluble Enters the portal system Long chain fatty acids reforms into TG Enters the lymphatic system Carrying Fat in the Bloodstream Water (blood) and oil (fat) are incompatible Unique system of fat transportation is needed Transportation of Digested Fat Re-formed into triglycerides Packaged into chylomicrons Lipoprotein lipase breaks down triglycerides in the chylomicrons Fatty acids are absorbed by cells Takes 2-10 hours to clear chylomicron Lipoproteins Transportation of Synthesized Fat Fat and cholesterol made primarily by the liver Very Low Density Lipoprotein (VLDL) Low Density Lipoprotein (LDL) Receptor pathway for cholesterol uptake Scavenger pathway for cholesterol uptake Scavenger Pathway Scavenger WBC removes (oxidized) LDL from circulation Prevents oxidized LDL from returning to circulation Build-up of plaque on walls of the blood vessels Leads to plaque and atherosclerosis Causes: smoking, diabetes, HTN, homocysteine, LDL Antioxidant Reduces oxidation Slows LDL uptake into scavenger cells Need for supplements of antioxidants? High Density Lipoprotein (HDL) Synthesized by liver and intestine High proportion of protein Picks up cholesterol from dying cells and other sources Transfers cholesterol to other lipoprotein for transport to the liver for excretion HDL can also transfer directly back to the liver Benefits of (a high) HDL (level) Remove cholesterol from the blood stream HDL may block oxidation of LDL Reduce risk of heart disease Pre-menopausal women have higher HDL Functions of Lipids Provide energy Efficient storage of energy Insulation Protection Transport fat-soluble vitamins Satiety Flavor and mouth feel 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) Cis and Trans Fatty Acid Health Dangers of Excessive Trans Fatty Acid Raises LDL Lowers HDL Increases risk for heart disease Current intake is~3% of total kcals Soon to be on food labels Minimize Intake of Trans Fatty Acid Limit use of hydrogenated fats Limit deep-fried foods Limit high fat baked goods Limit use of non-dairy creamers Rancidity Decomposed oils Breakdown of the C=C double bonds by ultraviolet rays, &/or O2 Yields unpleasant odor and flavor PUFA more susceptible Limits shelf life Prevention of Rancidity Hydrogenation Addition of vitamin E Addition of Butylated hydroxyanisol (BHA) and Butylated hydroxytolune (BHT) Recommendation No RDA 4% of total kcal should come from essential fatty acids No more than 15% from PUFA Current diet supplies ~33% of total kcal from fat much from animal, whole milk, pastries, cheese, margarine, and mayo The American Heart Association For high risk individuals <20-30% of total kcal from fat/day <7-10% from saturated fat (includes trans fatty acid) <200-300 mg cholesterol a day The National Cholesterol Education Program Reduce saturated fat intake to 7% of total energy Reduce cholesterol to 200 mg/day Other Recommendations Fat intake can be higher as long as saturated and trans fatty acid are minimal Eat diet with plenty of fruits and vegetables Cut down on red meats Cut down on simple sugars and refined CHO Signs of a Heart Attack Intense, prolong chest pain Shortness of breath Sweating Nausea and vomiting Dizziness Weakness Jaw, neck, shoulder pain Irregular heartbeat Cardiovascular Disease Symptoms take years to develop Plaque build-up can begin in childhood Myocardial infarction (heart attack) Cerebrovascular accident (stroke) The Road to a Heart Attack Risk Factors for Heart Disease Family history Smoking (even second hand) High blood pressure High blood cholesterol (hyperlipidemia) >200 mg/dl of total cholesterol HDL < 40 mg/dl Diabetes Lack of regular exercise and obesity Reducing Your Risks--Primary Prevention Reduce dietary saturated fat and cholesterol Increase MUFA and PUFA to recommended amounts Increase dietary fiber Increase activity; develop a exercise routine Adequate caloric intake to maintain healthy weight Secondary Prevention (After a Heart Attack) Primary prevent techniques Medication Hormone therapy Megadoses of vitamin E (400-800 IU/day) Lowering LDLs See your doctor to assess for other conditions Reduce dietary saturated fat and cholesterol Increase MUFA and PUFA Increase dietary fiber (soluble) Lowering Blood TG Is the most diet-responsive blood lipid Overeating Limit alcohol Limit simple sugars Small frequent meals Include fish in the diet Raise the HDL Physical activity At least 45 min./day, 4 days a week Avoid smoking Eat regularly Eat less total fat Moderate intake of alcohol increases HDL Other Possible Methods Cholestin (from Chinese red yeast) reduces cholesterol Benecol and Take Control margarine Plant stanol/sterol esters Cholesterol-lowering effects Decrease absorption of cholesterol and lowers amount returning via enterohepatic circulation. Liver takes up more cholesterol from the blood Strategies for Reducing the Risk Eat less saturated fat & trans fatty acids Replace with MUFA and essential fatty acids Eat fish 2x a week Eat plenty of fruits and vegetables Eat more whole grains and less refined CHO Eat at least 3 meals regularly Strategies Consume moderate alcohol Moderation in coffee, replace with tea Moderation in salt Meet calcium needs Avoid excess iron intake