Fish oil(Omega 3 fatty acids) are produced out of the flesh of oily fish, Fish oil can be taken as part of a proper diet as it consists of the omega-3 fatty acids, eicosapentaenoic acid(EPA), as well as docosahexaenoic acid(DHA). These are precursors to eicosanoids which have been known to decrease inflammation in the human body.
Fish do not in fact generate omega-3 fatty acids. Instead, they build up omega-3 in two ways: Either from eating microalgae which create essential fatty acids (with fish such as sardines and herrings), or else from eating larger pelagic and predatory fish which themselves have built up omega-3 fatty acids through eating microalgae.
Over time, fish oil has attracted plenty of attention in research and studies in the treatment of clinical depression,(specifically bipolar disorder), as well as cardiovascular health where studies have shown that fish oil may be able to regulate cholesterol in the body.