Human Requirement for N-3 Polyunsaturated Fatty Acids

Abstract

The diet of our ancestors was less dense in calories, being higher in fiber, rich in fruits, vegetables, lean meat, and fish. As a result, the diet was lower in total fat and saturated fat, but contained equal amounts of n-6 and n-3 essential fatty acids. Linoleic acid (LA) is the major n-6 fatty acid, and alpha-linolenic acid (ALA) is the major n-3 fatty acid. In the body, LA is metabolized to arachidonic acid (AA), and ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ratio of n-6 to n-3 essential fatty acids was 1 to 2:1 with higher levels of the longer-chain polyunsaturated fatty acids (PUFA), such as EPA, DHA, and AA, than today's diet. Today this ratio is about 10 to 1:20 to 25 to 1, indicating that Western diets are deficient in n-3 fatty acids compared with the diet on which humans evolved and their genetic patterns were established. The n-3 and n-6 EPA are not interconvertible in the human body and are important components of practically all cell membranes. The N-6 and n-3 fatty acids influence eicosanoid metabolism, gene expression, and intercellular cell-to-cell communication. The PUFA composition of cell membranes is, to a great extent, dependent on dietary intake. Therefore, appropriate amounts of dietary n-6 and n-3 fatty acids need to be considered in making dietary recommendations. These two classes of PUFA should be distinguished because they are metabolically and functionally distinct and have opposing physiological functions; their balance is important for homeostasis and normal development. Studies with nonhuman primates and human newborns indicate that DHA is essential for the normal functional development of the retina and brain, particularly in premature infants. A balanced n-6/n-3 ratio in the diet is essential for normal growth and development and should lead to decreases in cardiovascular disease and other chronic diseases and improve mental health. Although a recommended dietary allowance for essential fatty acids does not exist, an adequate intake (AI) has been estimated for n-6 and n-3 essential fatty acids by an international scientific working group. For Western societies, it will be necessary to decrease the intake of n-6 fatty acids and increase the intake of n-3 fatty acids. The food industry is already taking steps to return n-3 essential fatty acids to the food supply by enriching various foods with n-3 fatty acids. To obtain the recommended AI, it will be necessary to consider the issues involved in enriching the food supply with n-3 PUFA in terms of dosage, safety, and sources of n-3 fatty acids.

Ovarian follicular development, lipid peroxidation, antioxidative status and immune response in laying hens fed fish oil-supplemented diets to produce n-3-enriched eggs

“…High concentrations of dietary n-3 fatty acids reduce the activity of the enzyme in the n-6 pathway and the conversion of linoleic into ARA. The decrease in ARA content could be important for human health, as this acid is a precursor of some proinflammatory eicosanoids (Simopoulos, 2000). The egg cholesterol content significantly differed due to dietary fish oil treatment (Table 2).…”

“…Introduction n-3-polyunsaturated fatty acids (n-3 PUFA) play an important role in human nutrition since they help to reduce the incidence of such lifestyle diseases as coronary artery diseases, hypertension and diabetes, as well as certain inflammatory diseases such as arthritis and dermatitis (Simopoulos, 2000). These diseases are an increasing problem in countries of the Middle East and North Africa, due to the dominance of animal fats and partially hydrogenated vegetable oils in the meals of the people of these countries.…”

The impact of incorporation of n-3 fatty acids into eggs on ovarian follicular development, immune response, antioxidative status and tibial bone characteristics in aged laying hens

“…This strategy has proved to be viable and is currently applied to market eggs in several countries to improve the health image of eggs. Consumption of n-3 polyunsaturated fatty acids (n-3PUFA) has positive effects on health, including potential in prevention and treatment of cardiovascular diseases, diabetes, arthritis and certain types of cancer (Simopoulos, 2000). The balance between the two major types, n-6 and n-3PUFA, may also be crucial.…”

“…The balance between the two major types, n-6 and n-3PUFA, may also be crucial. According to the health point of view, Simopoulos (2000) stated that foodstuffs with an n-6/n-3 PUFA ratio of less than 4:1 are considered beneficial to -E-mail: tarkamin@gmail.com human health. Lewis et al (2000) and Kralik et al (2008) indicated a desirable ratio of n-6/n-3 PUFA of less than 4:1 in egg yolk lipids.…”

“…eicosapentaenoic acid (EPA; C20:5 n-3) and docosahexaenoic acid (DHA; C22:6 n-3)) and LO contains only a-linolenic acid (ALA; 18:3n-3), in greater amounts, which is the precursor of EPA and DHA. The ALA is converted into EPA and DHA by the hen's liver and the synthesized fatty acids are subsequently excreted with the egg yolk (Simopoulos, 2000).…”