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An omega−3 fatty acid is a fatty acid with multiple double bonds, where the first double bond is between the third and fourth carbon atoms from the end of the carbon atom chain. "Short-chain" omega−3 fatty acids have a chain of 18 carbon atoms or less, while "long-chain" omega−3 fatty acids have a chain of 20 or more.
Omega−3 fatty acids are important for normal metabolism. [ 2 ] Mammals are unable to synthesize omega−3 fatty acids, but can obtain the shorter-chain omega−3 fatty acid ALA (18 carbons and 3 double bonds) through diet and use it to form the more important long-chain omega−3 fatty acids, EPA (20 carbons and 5 double bonds) and then from ...
For instance, α-linolenic acid is an 18:3 fatty acid and its three double bonds are located at positions Δ 9, Δ 12, and Δ 15. This notation can be ambiguous, as some different fatty acids can have the same C:D numbers. Consequently, when ambiguity exists this notation is usually paired with either a Δ x or n−x term. [13]
The first double bond is located at the third carbon from the methyl end of the fatty acid chain, known as the n end. Thus, α-linolenic acid is a polyunsaturated n−3 (omega-3) fatty acid. It is a regioisomer of gamma-linolenic acid (GLA), an 18:3 (n−6) fatty acid (i.e., a polyunsaturated omega-6 fatty acid with three double bonds).
Intake of large doses (2.0 to 4.0 g/day) of long-chain omega−3 fatty acids as prescription drugs or dietary supplements are generally required to achieve significant (> 15%) lowering of triglycerides, and at those doses the effects can be significant (from 20% to 35% and even up to 45% in individuals with levels greater than 500 mg/dL).
Omega-3 fatty acids have a double bond three carbons away from the methyl carbon, whereas omega-6 fatty acids have a double bond six carbons away from the methyl carbon. The illustration below shows the omega-6 fatty acid, linoleic acid. Polyunsaturated fatty acids can be classified in various groups by their chemical structure:
Cervonic acid (or docosahexaenoic acid) has 22 carbons, is found in fish oil, is a 4,7,10,13,16,19-hexa unsaturated fatty acid. In the human body its generation depends on consumption of omega 3 essential fatty acids (e.g., ALA or EPA), but the conversion process is inefficient. [ 22 ]
Docosahexaenoic acid (DHA) is an omega−3 fatty acid that is an important component of the human brain, cerebral cortex, skin, and retina. It is given the fatty acid notation 22:6( n −3) . [ 1 ] It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk (breast milk), fatty fish, fish oil, or algae oil.