According to research conducted at Harvard University, omega-3 fatty acid deficiency is officially one of the top 10 causes of death in America, claiming the lives of up to 96,000 people each year. Out of the 12 dietary, lifestyle and metabolic risk factors examined in the study, omega-3 fatty acid deficiency ranked as the sixth highest killer of Americans. (1) These deaths are considered preventable since getting enough omega 3-fatty acids in your diet can ward off this now common cause of death, and fish oil benefits omega-3 intake as a potent omega-3 source.
2. Omega-3 normalizes and regulates your cholesterol triglyceride levels. Compared to a statin, both fish oil and krill oil are more efficient in doing this. According to a study comparing the efficiency of krill and fish oils in reducing triglyceride levels,7 both oils notably reduced the enzyme activity that causes the liver to metabolize fat, but krill had a more pronounced effects, reducing liver triglycerides significantly more.
Pregnancy and breast-feeding: Fish oil is LIKELY SAFE when taken by mouth appropriately. Taking fish oil during pregnancy does not seem to affect the fetus or baby while breast-feeding. Women who are pregnant or who may become pregnant, and nursing mothers should avoid shark, swordfish, king mackerel, and tilefish (also called golden bass or golden snapper), as these may contain high levels of mercury. Limit consumption of other fish to 12 ounces/week (about 3 to 4 servings/week). Fish oil is POSSIBLY UNSAFE when dietary sources are consumed in large amounts. Fatty fish contain toxins such as mercury.
Results of studies investigating the role of LCPUFA supplementation and LCPUFA status in the prevention and therapy of atopic diseases (allergic rhinoconjunctivitis, atopic dermatitis and allergic asthma) are controversial; therefore, at the present stage of our knowledge (as of 2013) we cannot state either that the nutritional intake of n−3 fatty acids has a clear preventive or therapeutic role, or that the intake of n-6 fatty acids has a promoting role in context of atopic diseases.[64]
Higdon JV, Liu J, Du S, et al. Supplementation of postmenopausal women with fish oil rich in eicosapentaenoic acid and docosahexaenoic acid is not associated with greater in vivo lipid peroxidation compared with oils rich in oleate and linoleate as assessed by plasma malondialdehyde and F(2)- isoprostanes. Am J Clin Nutr 2000;72:714-22. View abstract.

Preventing re-blockage of blood vessels after angioplasty, a procedure to open a closed blood vessel. Research suggests that fish oil decreases the rate of blood vessel re-blockage by up to 45% when given for at least 3 weeks before an angioplasty and continued for one month thereafter. But, when given for 2 weeks or less before angioplasty, it doesn't seem to have any effect.