Essential Fatty Acids
ESSENTIAL FATTY ACIDS
Two polyunsaturated fatty acids, linoleic acid and arachidonic acid (omega 3, omega 6 and omega 9), are the only fatty acids known to be essential for the nutritional well being of many species of animals, and of the humans. Linoleic acid (omega 3) cannot be synthesized and must therefore be supplied in the diet, but arachidonic acid (omega 6 and omega 9) can be formed from linoleic acid in the animal body. Linoleic acid occurs in high concentrations in various edible vegetable oils, e.g., corn, cottonseed, peanut, safflower, soybean (but not in olive oil or coconut oil), whereas arachidonic acid occurs in animal fats, albeit in rather small amounts. Essential fatty acid deficiency has been produced in animals and man by restricting essential fatty acid intake. Signs of deficiency in omega 3 in experimental animals include poor growth, dermatitis, poor reproductive performance, lowered caloric efficiency, decreased resistance to a number of stress conditions, and impairment in lipid transport. Dermatitis and derangement’s in lipid transport have also been seen in man as a result of lower omega 6 diet ingesting experimental diets that were virtually free of essential fatty acids. Deficiency has not been reported in human adults on ordinary diets. However, deficiencies have been reported in hospitalized patients maintained exclusively on intravenous feeding for prolonged periods (Collins et al., 1971; Paulsrud ci al., 1972).
Essential fatty acids especially omega 9 seem to play a role in the regulation of cholesterol metabolism, especially transport, transformation into metabolites, and ultimate excretion. Diets high in polyunsaturated fatty acids (including the essential fatty acids) have been shown to reduce serum cholesterol in experimental animals and in man, although the ultimate fate of the cholesterol removed from the circulation has not as yet been established. In tissue metabolism, essential fatty acids in phospholipids are important for maintaining the function and integrity of cellular and sub-cellular membranes. In addition, essential fatty acids (omega 6 and omega 9) have been shown to be precursors for a group of hormone-like compounds called prostaglandins, which are important in the regulation of widely diverse physiological processes.
Studies with both human subjects and animals indicate that, to prevent deficiency, the required intake of essential fatty acids lies within the range of 1—2 percent of total calories. This amount in the diet is not difficult to achieve.