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 H20

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

R + H20

Triglycerides

esterification desterfication

H

H--C--OH

H--C--OH

H--C--OH

H

Fatty Acid

Fatty Acid

Fatty Acid

+

H O

H--C--O--C--

O

H--C--O--C--

O

H--C--O--C--

H

Fatty Acid

Fatty Acid

Fatty Acid

Monounsaturated Fatty Acid Structure

omega end alpha 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 end alpha 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 6 - 10 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 end

alpha 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 end

alpha 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

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 acidincrease 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