Essentials of Nutrition for Sports

Linoleic acid deficiency is associ

ated with growth deficiencies

and skin problems.

Linoleic acid is widespread in plants and seed oils; arachidonic

acid is found mainly in meats, egg yolk, and some fish. Alpha-Linolenic Acid

The only known function of alpha-linolenic acid is to serve as a

precursor for the synthesis of the long-chain omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid.

For detailed information, see

Omega-3 Fatty Acids

on page

81

.

Docosahexaenoic Acid

Docosahexaenoic acid is a conditionally essential nutrient. Its

production from alpha-linolenic aci

d may be inadequate to meet

needs for brain growth in early human development and it confers functional benefit even when alpha-linolenic acid is in the diet.

Both docosahexaenoic acid and arachidonic acid are available in

breast milk and in many infant formulas.

For detailed information, see

Omega-3 Fatty Acids

on page

81

.

Long-Chain Polyunsaturated Fatty Acids

Long-chain polyunsaturated acids have several roles:

-^

Oxidation to provide energy

-^

Triglyceride synthesis and limited tissue storage

-^

Phospholipids in membranes, particularly neural tissue

-^

Eicosanoid synthesis: prostaglandins, thromboxanes, leukotrienes

Membranes

As structural components of membranes, arachidonic acid and

docosahexaenoic acid influence the functional characteristics of tissues, particularly neural tissues.

Docosahexaenoic acid is concentrat

ed in the outer segment of

the rods in the retina of the ey

e. The presence of docosahexaenoic

acid is related to light activation and visual processing.

For detailed information, see

Omega-3 Fatty Acids

on page

81

.

Eicosanoids

Arachidonic acid is the major precursor for the synthesis of

eicosanoids, cellular regulatory substances and mediators of inflammation that include prostaglandins, thromboxanes, and leukotrienes.

Eicosanoids are involved in platelet aggregation, T-cell

proliferation, lymphocyte migrati

on, vasoconstriction and dilation,

and the production of several immune and inflammatory substances.

In the presence of eicosapentaenoic acid, eicosanoids derived

from the omega-3 family are also produced. These attenuate or inhibit the action of the arachidonic acid -derived eicosanoids. Those derived from eicosapentaenoic acid have weaker biological activity than those from arachidonic acid.

Competition from omega-3 fatty acids for the same eicosanoid

synthesizing enzymes may reduce the production of omega-6 eicosanoids.

Eicosapentaenoic acid can moderate the production and activity

of arachidonic acid–derived eicosanoids.

The predominance of eicosanoids derived from omega-6 fatty

acids may contribute to chronic diseases, including heart disease.

For detailed information, see

Omega-3 Fatty Acids

on page

81

.

Toxicity Cardiovascular Diseases

See

Heart-Healthy Fat

on page

87

.

Nutrition for Sports, Essentials of 80