Essential fatty acids are necessary for various aspects of normal physiology like: mediating immune response, regulating bodily secretions and their viscosity, dilating and constricting blood vessels, regulating collateral circulation, directing endocrine hormones to their target cells, regulating smooth muscles and autonomic reflexes, being primary constituents of cell membranes, regulating the rate of cell division, maintaining the fluidity and rigidity of cellular membranes, regulating the flow of substances into and out from cells, transporting oxygen from red blood cells to the tissues, maintaining proper kidney function and fluid balance, keeping saturated fats mobile in the bloodstream, preventing blood clots, mediating the release of inflammatory eicosanoids that may trigger allergic conditions, and regulating nerve transmission and communication. (Source: Fish Oil: The Natural Anti-inflammatory by Joseph C. Maroon and Jeffrey Bost, 2006, page 39).
For this reason, it is very important for over-all health to have a regular intake of foods rich in omega-6 or omega-3 EFAs. The omega-3 pathway, activated by trauma, injury, or chemical stimulus, is the process of converting the omega-3 EFAs found in the cell membranes to various eicosanoids. If the omega-3 EFA components of the cell membranes become dominant, an anti-inflammatory state can result, with preventive health benefits.
Fish oil is the best source of the omega-3 essential fatty acids. But why fish oil, you might ask? The needed nutrients can also be found in green plants; algae (phytoplankton); leaves and seeds of the perilla plants; and linseed oil but fish oil is considered the most important dietary source of omega-3 EFAs because it contains concentrated amounts of the ALA derivatives with APA and DHA.
The two mentioned nutrients can almost exclusively found in seafood. Fish contains high amount of EPA and DHA because they are at the top of food chain based on algae, a single-marine organism that manufactures huge amount of EPA and DHA.