Optimum fish oil is a natural supplement filled with Omega-3 essential fatty acids. Fatty acids are the basis of fats and oils, and, despite popular belief, are necessary for overall health. These fatty acids are termed essential because your body cannot manufacture them by itself. EFAs must come from food or supplemental sources. They are also essential because they are a component of every living cell in the body, and are necessary for rebuilding existing cells and the production of new cells. Studies show fish oil supports healthy heart function and joint flexibility.