Omega-3 Fatty Acids in Metabolism, Health, and Nutrition and for Modified Animal Product Foods

Abstract

<h2>ABSTRACT</h2> Fatty acids, n-3 as well as n-6, are essential for normal physiological functioning and for the health of humans and all domestic species. It is important to emphasize an adequate linolenic acid (LNA) intake; the n-6:n-3 fatty acid ratio is not a useful concept, and it detracts from increasing absolute intakes of n-3 PUFA. In humans, when LNA is consumed in adequate amounts and without excessive n-6 fatty acids, conversion to eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids can maintain normal physiological functioning and health. However, conversion of LNA to EPA is more limited in humans than in rodent models, and conversion to DHA is even more limited. Stearidonic acid bypasses the limiting step in synthesis of EPA, but not DHA, from LNA. Therefore, development of gene-modified oil crops to increase content of stearidonic acid supply holds promise to increase EPA synthesis in humans. Quantitative synthesis of EPA and DHA from LNA in domestic animals has not been reported, but conversion is limited in these as well, although perhaps not for some aquatic species. In humans, evidence is clear that increased intake of the fish oil fatty acids, especially DHA, will improve physiological and health outcomes during pregnancy and lactation, stresses of the immune system, cardiovascular disease, cancer, and some mental and emotional conditions. At least 200 mg DHA should be consumed daily by pregnant and lactating women. Certain feed supplements increase the n-3 fatty acid content of animal products, including eggs, meat from major domestic species, and milk. Feeding flax (linseed or linseed oil) increases LNA content of products 2- to 3-fold, and in some products, EPA is also increased, with the exception of eggs, in which DHA, but not EPA, is increased. The increase is adequate to have a positive effect on the n-3 fatty acid intake of the general public. To change EPA, and especially DHA, significantly in animal products, fish oil or marine algae products must be fed. To achieve 2- to 3-fold increases in ruminant tissues and milk, supplementation with rumen-protected linseed or marine oil products is necessary. At higher levels of n-3 PUFA incorporation, effects on product quality (oxidative stability, sensory characteristics) and costs of production and segregation of modified from conventional products in the production and distribution streams must be considered. It seems possible that niche markets for products containing greater amounts of n-3 fatty acids can be developed without expensive protection processes and risks of decreased product quality.