Lipids Composed of C, H and few O Basic unit is fatty acid (glyceride) Triglyceride is the major form of lipid = 3 fatty acids Fats and oils Monounsaturated Fatty Acids Polyunsaturated Fatty Acids Saturated Fatty Acids Essential Fatty Acids Energy yielding (9 kcal /gm)

Sources of Dietary 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) Energy dense (9 kcal /gm)

The building block of lipids are fatty acids omega endalpha end Note that all carbons have two hydrogens – this is a fully saturated fatty acid. 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

Triglycerides (Ester bond) Glycerol + 3 FA’s Triglyceride + 3 H 2 0 H H--C--OH H--C--OH H--C--OH H O HO-C-R O HO-C-R O HO-C-R + H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H R + H2O R + H20

Triglycerides esterification desterfication 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

Monounsaturated Fatty Acid Structure omega endalpha end When two Hs are lost from two adjacent Carbons, a double bond is formed. This is an unsaturated fatty acid. 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 Two or more double bonds results in a polyunsaturated fatty 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

The more double bonds, the lower the melting point of a fat/oil Beef fat or lard has a large amount of saturated fatty acids that are long. It is solid at room temperature. Butter has about the same number of saturated as unsaturated fatty acids. Butter is beginning to melt at room temperature. Vegetable oil is 100% unsaturated fatty acids. It is liquid at room temperature and will solidify at around –5 °F. What about vegetable shortening?????

The chain length has an effect on how liquid a fat/oil is at room temperature Long chain FA > 12 Carbons Medium chain FA Carbons Short chain FA < 6 Carbons

Hydrogenation of Fatty Acids Process used to solidify an oil Addition of H to C=C double bonds Formation of 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 –partially hydrogenated vegetable oil Limit deep-fried foods Limit high fat baked goods Limit use of non-dairy creamers

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 endalpha 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 Acids Primarily from fish oil Also found in canola or soybean oil Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are related Metabolized to form eicosanoids Recommend intake of ~2 servings of fish per week

Omega 3 (Alpha-linolenic acid, C18:3) 2C 2H Eicosapentaenoic acid (EPA, C20:5) 2C 2H Docosahexaenoic acid (DHA, C22:6) Eicosanoids

Essential Fatty Acid Omega-6 (alpha-linoleic acid) omega endalpha 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 and meat Only need ~ 1 tablespoon a day Arachidonic acid can be made from omega-6 (18:2  6) Metabolized to form certain eicosanoids

Omega 6 (linoleic acid, C18:2) 2C 2H Dihomo-gamma-linolenic acid (C20:3) 2H Arachidonic acid (C20:4) Eicosanoids

Eicosanoids are a group of hormone-like compounds Regulators of blood pressure, childbirth, clotting, immune responses, inflammatory responses, & stomach secretions By-pass the blood stream and work in the area of origin

Eicosanoids Have Different Effects Omega-6 eicosanoids; Archidonic acid increase blood cot increase inflammatory responses Omega-3 eicosanoids, DHA, EPA decrease blood clotting reduces heart attack excess may cause hemorrhagic stroke??? Eicosanoids have different effects on different tissues

Signs and Symptoms of Essential Fatty Acids Deficiency Flaky, itchy skin Diarrhea Infections Retarded growth and wound healing Anemia

Phospholipids 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 Makes up cell membrane Eicosanoid synthesis Emulsifier Bile acids Lecithins

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

Emulsification (Fig. 6-5) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Cell Membrane Double layers of lipid, CHO, and protein Controls passage of substances Distinct identification structures

Sterols 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

Digestion of Lipids Where do dietary lipids go? How does our body make lipid? Where do lipids that our bodies make go?

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 Pancreatic colipase is release to help facilitate lipase enzyme action CCK stimulates the release of bile to help emulsify fat Fat is broken down to monoglycerides and fatty acids

Transportation of Fat in the Bloodstream Water (blood) and oil (fat) are incompatible Unique system of fat transportation is needed Fat

Transportation of Dietary Fat What we do with it directly after eating it… Re-formed into triglycerides Packaged into chylomicrons Lipoprotein lipase breakdown triglycerides in the chylomicrons Fatty acids are absorbed by cells Takes 2-10 hours to clear chylomicron

Dietary Fat Absorption

Nutrient Absorption

Lipoproteins

Transportation of Synthesized Fat Fat and cholesterol made primarily by the liver Very Low Density Lipoprotein (VLDL) VLDL remnant (or IDL) Low Density Lipoprotein (LDL) Receptor pathway for cholesterol uptake Scavenger pathway for cholesterol uptake

Receptor 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 atherosclerosis Causes: smoking, diabetes, HTN, homocysteine, LDL Scavenger Pathway

Antioxidant Reduces oxidation Slows LDL uptake into scavenger cells Need for supplements of antioxidants?

Composition of Lipoproteins

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

Rancidity Decomposed oils Breakdown of the C=C double bonds by ultraviolet rays, O 2 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)

American Heart Association’s Recommendations No RDA for fat < 30% of total energy intake (TEI) from all fats 8% -10% of TEI from saturated fat < 10% of TEI from PUFA < 15% of TEI from MUFA < 300 mg cholesterol /day Limit intake of trans fatty acid Low fat is not recommended for children under 2 years of age

The National Cholesterol Education Program Reduce fat intake to 7% of total energy intake from saturated fat if elevated LDL does not respond to previous reduction Limit cholesterol to ~300 mg/day Reduce cholesterol to 200 mg/day if LDL remains high

Here fat, there fat, everywhere fat, fat Read labels carefully Use of monoglycerides and diglycerides in foods High in nuts, cheeses, fatty meats, whole milk

Reduce Fat Labels “Low fat” < 3 gm of fat/serving “Reduced fat” or “Less fat” > 25% less fat than reference food “Fat free” < 0.5 gm of fat/serving

“Fat Free” = “All You Can Eat”? Sales of reduced-fat foods are projected to soar to ~$32 billion by year 2001 When fat is removed, sugar is usually added in its place “Fat Free” is NOT “Calorie Free” Calorie content is still similar to full-fat version Eat “Reduced-fat” foods in moderation

Fat Substitutes Z-trim Starch derivative Binds with water to create mouth-feel Contains less calorie than fat

Fat Substitutes Simplesse Egg and milk protein globules High water content 1-2 kcal/gm Not heat stable

Fat Substitutes Olestra (Olean) Engineered fat Fatty acids linked to sucrose Not digested by enzymes or bacteria Yields no calories Addition of fat soluble vitamins Over-consumption may cause cramping and loose stool May bind to carotenoids in the meal

Uses for Fat Substitutes Use in moderation Use in place of high fat option Avoid over-eating Treat it as you would a full fat food

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

Coronary Heart Disease Symptoms take years to develop Plaque build-up can begin in childhood Myocardial infarction (heart attack) Stroke

Conditions Leading to a Heart Attack

Risk Factors for Heart Disease Family history Smoking High blood pressure High blood cholesterol (hyperlipidemia) >200 mg/dl of total cholesterol HDL < 35 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 ( IU/day)

Myth: Women Don’t Die of Heart Disease 44% of women die from cardiovascular disease (versus 38% in men) 33% of women die from heart disease(versus 31% in men) Doctors are more likely to consider heart disease for men (than women) Men develop heart disease earlier in life Early research focused on men

Benefits of Female Hormones? Not fully understood Decrease LDL Increase HDL Estrogen is associated with decrease risk Women’s risk for heart disease increases after menopause Estrogen therapy

Medical Therapy Cholestin (Mevacor) Derived from Chinese red yeast Successful in reducing blood cholesterol Pure cholestin is very expensive Benecol and Take Control Plant sterol ester Cholesterol-lowering effect Compete with cholesterol in the micelle and reduce absorption of dietary cholesterol

Other Strategies Healthy body weight Moderate to vigorous physical activity daily nonsmoker Alcohol in moderation Intakes of cereal fiber, omega-3 fatty acids, and folate Low intakes of sat. fat and higher intakes of PUFAs Low glycemic index load

CVD Detection C-reactive protein (hs-CRP) Measures protein made in the liver in response to inflammation Inexpensive Fast CT-scan X-ray revealing calcium deposits (plague composition) Expensive