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 end alpha 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 Only need ~ 1 tablespoon a day Arachidonic acid can be made from omega- 6 Metabolized to form 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??? Eicosanoid has different effect on different tissues

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