For the most part, organisms cansatisfy their own fatty acid needs. In mammals, however, those enzymes whichinsert double bonds into the chains of fatty acids cannot insert them into theomega-3 and omega-6 positions. Linoleic and linolenic acid contain omega-6 and3 bonds and are necessary for mammalian metabolism. These two fatty acids aretherefore essential fatty acids (EFA) and must be supplied by the diet.

Variations among species andwithin species occur in terms of what is or is not essential and at whatlevels. For example, the cat is limited in its ability to synthesizearachidonic acid (AA, 18:4w6). 1,2 Humans are unable to synthesize sufficientfatty acids with double bonds closer to the methyl end than omega-9. Varyingcapabilities occur even within species. 3 A diet satisfactory for oneindividual may not be for another, since enzyme systems regulating synthesisand metabolism vary with individual genetics.

Varying environmentalcircumstances may also alter needs. A sufficient diet this week may not be sonext week if circumstances change. The consumption of alcohol or medications,the presence of disease, atrophy, increased stress, increased consumption oftrans- fatty acids (present in all foods containing partially hydrogenatedoils), dieting, obesity, allergy, young age, old age, high cholesterol, and soforth can all alter nutrient requirements. 4 There is no such thing as anaverage requirement which fits everyone all the time.

Some factors affect dietary intakewhile others affect the ability of essential fatty acids, once consumed, toconvert through the steps necessary to form their physiologically important endproducts. For example, LA (18:2w6) consumed must first be converted to gammalinolenic acid (GLA, 18:3w6) by desaturase enzymes, and then on to otherproducts by enzymes to form important eicosanoids such as prostaglandins. Manyfactors (stress, disease, allergy, etc.) can interfere with this first stepmediated by delta-6-desaturase to create GLA. 5 Therefore, for someindividuals, GLA or its progeny may have to be directly supplied to the dietthus by-passing the need for this enzyme. This is the rationale for the use ofthe supplement evening primrose oil since it contains high levels of GLA. Otheroil sources such as black currant seed, borage, and fish also supply fattyacids which skip several steps in these metabolic pathways and thus may beimportant dietary components for some individuals (animals and people). (Fig. 13)

[ Fatty Acid Essentiality Image ]

http://www.wysong.net/articles/lipid/figures/figure13.jpg

An important component of fishoil, for example, eicosapentaenoic acid (EPA, 20:5w3) may become a dietaryessential if age or other factors limit the ability to convert dietaryplant-derived LNA (l8:3w3) into EPA, which is the precursor to severalimportant omega-3 derived eicosanoids.

Although not considered essentialfatty acids in the sense of LA and LNA, there are at least four otherunsaturated fatty acids in nutrition now recognized as playing key biochemicalroles, and for which there may be an essential requirement for someindividuals. These are oleic acid (OA, 18: 1w9), gammalinolenic acid (GLA,18:3w6), eicosapentaenoic acid (EPA, 20:5w8), and docosahexaenoic acid (DHA,22:6w3). This list is surely incomplete.

Note that OA is a mono-unsaturatedcompound (one double-bond), GLA has three double bonds, and EPA and DHA havefive and six double bonds, respectively. (Fig. 5) Linolenic acid (manufacturedonly in plant chloroplasts) as well as EPA and DHA belong to the omega-3 familyof fatty acids; LA and GLA, as well as arachidonic acid (AA: 20: 4w6), aremembers of the omega-6 family. Oleic acid is a member of the omega-9 family.All these fatty acids have great biochemical significance and theunderstanding of their metabolic roles is increasingly demonstrating their linkto health and disease.

The essentiality of fatty acids,like that of all other nutrients, is linked to many variables. Requiredamounts and types of fatty acids can vary among species and even for the sameindividual. Diets rich in unaltered fatty acids (particularly raw whole foods)and specific properly prepared fatty acid supplements (a second choice) canprovide sufficient fatty acid substrate for optimal health.

References available within booktext, click the following link to view this article on wysong.net:

http://www.wysong.net/articles/lipid/04_article_lipid_chapter_four_essential_fatty_acids.shtml

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Article Tags: acid | fatty | acids | diet | essential | omega | bond | linolenic | enzyme | dietary | oleic | factors | fatty acids | essential fatty | linolenic acid |
About the Author Dr. Wysong: A former veterinary clinician and surgeon, college instructor in human anatomy, physiology and the origin of life, inventor of numerous medical, surgical, nutritional, athletic and fitness products and devices, research director for the present company by his name and founder of the philanthropic Wysong Institute. http://www.wysong.net. Also check out http://www.cerealwysong.com.