Essentials of Nutrition for Sports

Oleic acid is the monounsaturated fatty acid that occurs most
frequently in nature.

Of the polyunsaturated fatty acids, linoleic, linolenic,

arachidonic, eicosapentaenoic, and docosahexaenoic acids containing respectively two, three, four, five, and six double bonds are of the most nutritional interest.

Unsaturated fatty acids, common name, number double bonds,

carbon chain length, and typical source are listed in

Table 11

.

Naming Omega, N-Minus System

In the omega or “n-minus” system, the first number is the length

of the fatty acid chain; the second number, after a colon, is the number of double bonds.

A third number, after, “n minus,” indicates the position of the

first double bond counting from the methyl or omega end of the molecule.

The most common are the omega-3 and omega-6 fatty acids. Location of the first double bond end determines whether the

fatty acid is an omega-3 or omega-6 fatty acid.

For example, linoleic acid is 18:2n-6. Linoleic acid is an 18-

carbon omega-6 fatty acid with two double bonds. It is abundant in plants and in vegetable and seed oils.

Alpha-linolenic acid is 18:3n-3. Alpha-linolenic acid is an 18-

carbon omega-3 fatty acid with three double bonds. It is found in plants and oils.

Eicosapentaenoic acid, found in many fish oils, is an omega-3

fatty acid.

Oleic acid, which has its double bond 9 carbons from the methyl

end, is considered an omega-9 (or an n-9) fatty acid.

IUPACE System

In the International Union of Pure and Applied Chemistry

(IUPAC) system of nomenclature, the carbons in a fatty acid chain are numbered consecutively from the end of the chain, the carbon of the carboxyl group being considered as number 1.

By convention, a specific bond in a chain is identified by the

lower number of the two carbons that it joins. In oleic acid (

cis

-9-

octadecenoic acid), for example, the double bond is between the ninth and tenth carbon atoms.

When two fatty acids are identi

cal except for the position of the

double bond, they are referred to as positional isomers. Fatty acid isomers are discussed next.

Long-Chain Polyunsaturated Fatty Acids

These are fatty acids with 20 or more carbon atoms. Long-chain polyunsaturated fatty acids of the omega-6 family

are arachidonic acid (20:4n-6) and docosapentaenoic acid (22:5n-6).

Long-chain polyunsaturated fatty acids of the omega-3 family

are eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3).

Trans

Fat

Trans

fat is made when hydrogen is added to vegetable oil—a

process called hydrogenation.

Hydrogenation turns an unsaturated fat into a polyunsaturated fat

containing trans-fatty acids.

In nature, the hydrogen atoms at a double bond are usually

positioned on the same side of the carbon chain. This type of configuration is called

cis

(on this side

in Latin).

Partial hydrogenation reconfigures some double bonds and the

hydrogen atoms end up on different sides of the chain. This type of configuration is called

trans

(across

in Latin).

Nutrition for Sports, Essentials of 76