Essential Fatty Acids

Essential fatty acids are polyunsaturated fatty acids that the human body needs for metabolic functioning but cannot produce, and therefore has to be acquired from food.

Omega-3 and Omega-6 Fatty Acids

Omega-3 and omega-6 fatty acids are also referred to as n-3 and n-6 fatty acids, respectively.

Omega-3 fatty acids are a class of essential polyunsaturated fatty acids with the double bond in the third carbon position from the methyl terminal (hence the use of "3" in their description). Foods high in omega-3 fatty acids include salmon, halibut, sardines, albacore, trout, herring, walnut, flaxseed oil, and canola oil. Other foods that contain omega-3 fatty acids include shrimp, clams, light chunk tuna, catfish, cod, and spinach.

Omega-6 fatty acids are a class of essential polyunsaturated fatty acids with the initial double bond in the sixth carbon position from the methyl group (hence the "6"). Examples of foods rich in omega-6 fatty acids include corn, safflower, sunflower, soybean, and cottonseed oil. Heating omega-6 oils, such as corn oil, to high temperatures creates trans fats.  The intake of trans fatty acids increases blood LDL-cholesterol ("bad" cholesterol), decreases HDL cholesterol ("good cholesterol"), and raises the risk of coronary heart disease.

Benefits of Omega-3 Fatty Acids

Scientific evidence is mounting that fish oil (predominantly omega-3 fatty acids) can reduce the risk of sudden cardiac death.

Two controlled studies on omega-3 fatty acids and fish oil have recently been published. The GISSI-Prevention trial studied the effect of omega-3 fatty acids on sudden death and the recurrence of coronary heart disease in patients who recently survived a heart attack. The Lyon Diet Heart Study studied the effect of a Mediterranean diet on the recurrence of coronary heart disease in patients who recently survived a heart attack.

The GISSI-Prevention trial randomly assigned more than 11,000 patients with recent heart attacks to four treatment groups; omega-3 fatty acids (850 mg capsule daily), vitamin E, both, or neither (control). The study subjects in all four groups were followed for 3.5 years. Study results were published in Circulation, 2002; 105:1897-1903. Subjects given omega-3 fatty acids had a 20% lower death rate from coronary heart disease than subjects in the vitamin E and control groups. Omega-3 fatty acids were particularly effective in preventing sudden cardiac death (45% reduction in sudden cardiac death).

The Lyon Diet Heart Study randomly assigned 600 subjects who survived recent heart attacks to either the Mediterranean diet or a prudent Western diet (diet low in saturated fat and cholesterol). The Mediterranean diet is rich in omega-3 fatty acids, as well as monounsaturated fats, fruits, vegetables, and nuts. The study subjects were followed for 4 years.

The results of the study were published in Circulation, 1999; 99:779-785. The subjects eating the Mediterranean diet had more than a 50% reduction in sudden cardiac death and in repeat fatal or nonfatal heart attacks as compared to the Western diet group.

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