Chemical structure of eicosapentaenoic acid (EPA) Chemical structure of docosahexaenoic acid (DHA) An<unk>  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"<unk> s have a chain of 18 carbon atoms or less, while "long-chain"<unk> s have a chain of 20 or more. Three<unk> s are important in human physiology, α-linolenic acid (18:3, n-3; ALA), eicosapentaenoic acid (20:5, n-3; EPA), and docosahexaenoic acid (22:6, n-3; DHA). These three polyunsaturates have either<unk> , 5, or 6 double bonds in a carbon chain of 18, 20, or 22 carbon atoms, respectively. As with most naturally-produced fatty acids, all double bonds are in the cis-configuration, in other words, the two hydrogen atoms are on the same side of the double bond; and the double bonds are interrupted by methylene bridges (--), so that there are two single bonds between each pair of adjacent double bonds. List of<unk> s This table lists several different names for the most common<unk> s found in nature. Common name Lipid number Chemical name Hexadecatrienoic acid (HTA) 16:3 (n−3) all-cis-7,10,13-hexadecatrienoic acid α-Linolenic acid (ALA) 18:3 (n−3) all-cis-9,12,15-octadecatrienoic acid Stearidonic acid (SDA) 18:4 (n−3) all-cis-6,9,12,15-octadecatetraenoic acid Eicosatrienoic acid (ETE) 20:3 (n−3) all-cis-11,14,17-eicosatrienoic acid Eicosatetraenoic acid (ETA) 20:4 (n−3) all-cis-8,11,14,17-eicosatetraenoic acid Eicosapentaenoic acid (EPA) 20:5 (n−3) all-cis-5,8,11,14,17-eicosapentaenoic acid Heneicosapentaenoic acid (HPA) 21:5 (n−3) all-cis-6,9,12,15,18-heneicosapentaenoic acid Docosapentaenoic acid (DPA),Clupanodonic acid 22:5 (n−3) all-cis-7,10,13,16,19-docosapentaenoic acid Docosahexaenoic acid (DHA) 22:6 (n−3) all-cis-4,7,10,13,16,19-docosahexaenoic acid Tetracosapentaenoic acid 24:5 (n−3) all-cis-9,12,15,18,21-tetracosapentaenoic acid Tetracosahexaenoic acid (Nisinic acid) 24:6 (n−3) all-cis-6,9,12,15,18,21-tetracosahexaenoic acid
Omega-3 fatty acid
Omega-6 fatty acid
Cholic acid
Omega-3 acid ethyl esters
Fish oil
Fish oil 
Phytosterol
Saturated fat