Marine lipids
Marine lipids originate from the liver of lean white fish such as cod, the body of oily fish such as mackerel, and the blubber of marine mammals such as seal. These oils consists of saturated, monounsaturated and polyunsaturated fatty acids (PUFA). There are two classes of PUFA, namely, the omega-3 and omega-6 families, which are differentiated from one another based on the location of the double bond from the terminal methyl group of the fatty acid molecule. Unlike saturated and monosaturated fatty acids, which can be synthesised by all mammals, including humans, the PUFA cannot be easily synthesized in the body and it must be provided through the diet. The omega-3 family of PUFA is descended from linolenic acid while its omega-6 counterparts are descended
from linoleic acid. The unique feature that differentiates lipids of marine species from those of land animals is the presence of long-chain PUFA, namely, eicosapentaenoic acid (EPA; C20:5 ω3), docosahexaenoic acid (DHA; C22:6 ω3) and, to a lesser extent, docosapentaenoic acid (DPA; C22:5 ω3).
Consumption of marine oil results in a decrease in plasma lipids by reduced synthesis of fatty acids and low-density lipoproteins. It has also been suggested that marine oils may retard atherogenesis through their effect on platelet function, platelet-endothelial interactions and inflammatory response.