Home »

Omega-3 fatty acid

The meaning of «omega-3 fatty acid»

Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or n−3 fatty acids,[1] are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chemical structure.[2] They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology.[3][4] The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), found in plant oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both commonly found in oils of marine fish.[3] Marine algae and phytoplankton are primary sources of omega−3 fatty acids (which also accumulate in fish). Common sources of plant oils containing ALA include walnuts, edible seeds, and flaxseeds, while sources of EPA and DHA include fish and fish oils.[1]

Mammals are unable to synthesize the essential omega−3 fatty acid ALA and can only obtain it through diet. However, they can use ALA, when available, to form EPA and DHA, by creating additional double bonds along its carbon chain (desaturation) and extending it (elongation). Namely, ALA (18 carbons and 3 double bonds) is used to make EPA (20 carbons and 5 double bonds), which is then used to make DHA (22 carbons and 6 double bonds).[1][2] The ability to make the longer-chain omega−3 fatty acids from ALA may be impaired in aging.[5] In foods exposed to air, unsaturated fatty acids are vulnerable to oxidation and rancidity.[2][6]

Dietary supplementation with omega−3 fatty acids does not appear to affect the risk of cancer or heart disease.[7] Furthermore, fish oil supplement studies have failed to support claims of preventing heart attacks or strokes or any vascular disease outcomes.[8][9]

The terms ω–3 ("omega–3") fatty acid and n–3 fatty acid are derived from organic nomenclature.[2][10] One way in which an unsaturated fatty acid is named is determined by the location, in its carbon chain, of the double bond which is closest to the methyl end of the molecule.[10] In general terminology, n (or ω) represents the locant of the methyl end of the molecule, while the number n–x (or ω–x) refers to the locant of its nearest double bond. Thus, in omega–3 fatty acids in particular, there is a double bond located at the carbon numbered 3, starting from the methyl end of the fatty acid chain. This classification scheme is useful since most chemical changes occur at the carboxyl end of the molecule, while the methyl group and its nearest double bond are unchanged in most chemical or enzymatic reactions.

In the expressions n–x or ω–x, the dash is actually meant to be a minus sign, although it is never read as such. Also, the symbol n (or ω) represents the locant of the methyl end, counted from the carboxyl end of the fatty acid carbon chain. For instance, in an omega-3 fatty acid with 18 carbon atoms (see illustration), where the methyl end is at location 18 from the carboxyl end, n (or ω) represents the number 18, and the notation n–3 (or ω–3) represents the subtraction 18–3 = 15, where 15 is the locant of the double bond which is closest to the methyl end, counted from the carboxyl end of the chain.[10]

Related Searches

Omega-6 fatty acid
Omega-7 fatty acid
Omega-9 fatty acid
Omega fatty acid
contact us full version