What is Omega-3?
~ October 2009 No.228 ~
It seems like just about everything you buy these days has omega-3 in it. So what really is an omega-3?
Fat – like you see on the edge of a steak, or that accumulates around your waist - is made up of fatty acids. Fatty acids are molecules that contain carbon, hydrogen, and oxygen atoms. One end of the fatty acid contains an acid group (-COOH) and the other end contains a methyl (-CH3) group. In between the acid group and the end methyl group, the carbon atoms can be joined by single or double bonds. If all the carbon bonds are single bonds, the fat is called saturated. Mono-unsaturates have one double bond. Poly-unsaturates have two or more double bonds.
The shorthand name for saturated fatty acids is straight forward. The number of carbon atoms in the molecule is indicated, followed by a colon and the number zero – no double bonds. For example palmitic acid is 16:0 (“sixteen zero”). There are 16 carbon atoms in palmitic acid, and no (zero) double bonds
For mono-unsaturated fatty acids, the number of carbon atoms in the molecule is again given, but the position of the one double bond also needs to be identified. Oleic acid is therefore referred to as 18:1ω9 (“eighteen one omega 9”). There are 18 carbon atoms in the molecule; there is one double bond and it is located 9 carbon atoms from the methyl end of the molecule. In some fatty acids the double bond is located 6 carbons from the methyl group. These fatty acids are called ?6 (“omega six”) fatty acids. When the double bond is 3 carbon atoms from the methyl group, the fatty acid is an ω3 (omega three).
Some fatty acids contain more than one double bond. Linoleic acid has 18 carbons and 2 double bonds. The first double bond is 6 carbons from the methyl group and so is represented as 18:2 ω6 (“eighteen two omega six”).
Eicosapentanoic acid (EPA), 20:5 ω3 (“twenty with five omega three”) has twenty carbon atoms and 5 double bonds, the first coming three carbons from the methyl group. Docosahexanoic acid (DHA) is 22:6 ω3
α-linolenic acid (ALA) – 18:3 ω3, EPA, and DHA are the most common omega three fatty acids that are found in foods. EPA and DHA can only be found in fish and algae. Flax oil is the best source of ALA
CH3-CH2-CH=CH-CH2……..COOH an ω3 fatty acid
CH3-CH2-CH2-CH2-CH2-CH=CH-CH2……..COOH an ω6 fatty acid
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-CH2……..COOH an ω9 fatty acid§
Omega-3 Fatty Acids - Fact Sheet for Health Professionals
National Institutes of Health