Essential fatty acids in health and chronic disease

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http://www.ajcn.org/cgi/reprint/70/3/560S.pdf

Am J Clin Nutr 1999 Sep;70(3 Suppl):560S-569S

Essential fatty acids in health and chronic disease.

Simopoulos AP

Center for Genetics, Nutrition and Health, Washington, DC 20009

Human beings evolved consuming a diet that contained about equal amounts of n-3

and n-6 essential fatty acids. Over the past 100-150 y there has been an

enormous increase in the consumption of n-6 fatty acids due to the increased

intake of vegetable oils from corn, sunflower seeds, safflower seeds,

cottonseed, and soybeans. Today, in Western diets, the ratio of n-6 to n-3 fatty

acids ranges from approximately 20-30:1 instead of the traditional range of

1-2:1. Studies indicate that a high intake of n-6 fatty acids shifts the

physiologic state to one that is prothrombotic and proaggregatory, characterized

by increases in blood viscosity, vasospasm, and vasoconstriction and decreases

in bleeding time. n-3 Fatty acids, however, have antiinflammatory,

antithrombotic, antiarrhythmic, hypolipidemic, and vasodilatory properties.

These beneficial effects of n-3 fatty acids have been shown in the secondary

prevention of coronary heart disease, hypertension, type 2 diabetes, and, in

some patients with renal disease, rheumatoid arthritis, ulcerative colitis,

Crohn disease, and chronic obstructive pulmonary disease. Most of the studies

were carried out with fish oils [eicosapentaenoic acid (EPA) and docosahexaenoic

acid (DHA)]. However, alpha-linolenic acid, found in green leafy vegetables,

flaxseed, rapeseed, and walnuts, desaturates and elongates in the human body to

EPA and DHA and by itself may have beneficial effects in health and in the

control of chronic diseases.