Abstract
Polyunsaturated fatty acids (PUFAs) contain ≥2 double-bond desaturations within the acyl chain. Omega-3 (n-3) and Omega-6 (n-6) PUFAs are the two known important families in human health and nutrition. In both Omega families, many forms of PUFAs exist: α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) from the n-3 family and linoleic acid (LA), dihomo-γ-linolenic acid (DGLA), and arachidonic acid (AA) from the n-6 family are the important PUFAs for human health. Omega-3 and Omega-6 PUFAs are competitively metabolized by the same set of desaturation, elongation, and oxygenase enzymes. The lipid mediators produced from their oxidative metabolism perform opposing (antagonistic) functions in the human body. Except for DGLA, n-6 PUFA-derived lipid mediators enhance inflammation, platelet aggregation, and vasoconstriction, while those of n-3 inhibit inflammation and platelet aggregation and enhance vasodilation. Overconsumption of n-6 PUFAs with low intake of n-3 PUFAs is highly associated with the pathogenesis of many modern diet-related chronic diseases. The volume of n-6 PUFAs is largely exceeding the volume of n-3PUFAs. The current n-6/n-3 ratio is 20-50/1. Due to higher ratios of n-6/n-3 in modern diets, larger quantities of LA- and AA-derived lipid mediators are produced, becoming the main causes of the formation of thrombus and atheroma, the allergic and inflammatory disorders, and the proliferation of cells, as well as the hyperactive endocannabinoid system. Therefore, in order to reduce all of these risks which are due to overconsumption of n-6 PUFAs, individuals are required to take both PUFAs in the highly recommended n-6/n-3 ratio which is 4-5/1.
Highlights
Polyunsaturated fatty acids (PUFAs) are fatty acids which contain two or more methylene-interrupted double-bond desaturations within the acyl chain [1, 2]
The objective of this review is to show the current status of the n-6/n-3 ratio imbalances in modern diets and their effect on the metabolic function of these fatty acid groups with relation to human health
Due to this higher n-6 consumption than n-3 PUFAs, modern diet-related chronic diseases have increased from time to time following the increasing unbalanced consumption ratio between these two families
Summary
Polyunsaturated fatty acids (PUFAs) are fatty acids which contain two or more methylene-interrupted double-bond desaturations within the acyl chain [1, 2]. The nutritionally important PUFAs for human health are members of the so-called Omega-3 (or n-3) and Omega-6 (or n-6) families [3] In both Omega families, many forms of PUFAs exists as shown, out of which the important forms for human health are α-linolenic acid (ALA, C18:3n-3), eicosapentaenoic acid (EPA, C20:5n-3), and docosahexaenoic acid (DHA, C22:6n-3) from the n-3 family, whereas linoleic acid (LA, C18:2n-6), dihomo-γ-linolenic acid (DGLA, 20:3n-6), and arachidonic acid (AA, C20:4n-6) from the n-6 family [2, 4]. N-3 PUFAs are sourced from green vegetables, wild ocean fish, oily seeds (chia, flax, and perilla), and foods derived from animals raised on green pasture [5,6,7]
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