“Lipid peroxidation induced by DHA enrichment modifies paracellular permeability in Caco-2 cells: protective role of taurine.” We conclude that hydrogen peroxide and peroxynitrite may be involved in the DHA-induced increase in paracellular permeability and that the protective role of taurine may be in part related to its capacity to counteract the effects of hydrogen peroxide.
Krill oil is a source of omega−3 fatty acids.[116] The effect of krill oil, at a lower dose of EPA + DHA (62.8%), was demonstrated to be similar to that of fish oil on blood lipid levels and markers of inflammation in healthy humans.[117] While not an endangered species, krill are a mainstay of the diets of many ocean-based species including whales, causing environmental and scientific concerns about their sustainability.[118][119][120]

36. Marchioli R, Barzi F, Bomba E, Chieffo C, Di Gregorio D, Di Mascio R, Franzosi MG, Geraci E, Levantesi G, Maggioni AP, et al. Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI)-Prevenzione. Circulation. 2002;105:1897–903. [PubMed]
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]
What about blood clotting? Circulating cells called platelets are critical in causing your blood to clot. When platelets are activated, they aggregate and cause clots. If these clots occur in particularly sensitive regions of your body, they can lead to a heart attack or stroke. EPA reduces platelet activation, an early step in platelet aggregation to help to reduce clotting. One study found that EPA was superior to DHA in decreasing platelet activation, a precursor to blood clotting.1

Because patients with depression experience rapid shrinking of their hippocampus, many strategies for relieving depression focus on increasing new brain cell growth in that specific area of the brain.23 There’s now evidence that increasing omega-3 intake, especially DHA, may be an effective way of treating or preventing depression, partly by protecting the hippocampus from further shrinkage.23
A Cochrane meta-analysis published in June 2012 found no significant protective effect for cognitive decline for those aged 60 and over and who started taking fatty acids after this age. A co-author of the study said to Time, "Our analysis suggests that there is currently no evidence that omega-3 fatty acid supplements provide a benefit for memory or concentration in later life".[43]
Khandelwal, S., Demonty, I., Jeemon, P., Lakshmy, R., Mukherjee, R., Gupta, R., Snehi, U., Niveditha, D., Singh, Y., van der Knaap, H. C., Passi, S. J., Prabhakaran, D., and Reddy, K. S. Independent and interactive effects of plant sterols and fish oil n-3 long-chain polyunsaturated fatty acids on the plasma lipid profile of mildly hyperlipidaemic Indian adults. Br.J.Nutr. 2009;102(5):722-732. View abstract.
Some studies suggest that people who get higher amounts of omega-3s from foods and dietary supplements may have a lower risk of breast cancer and perhaps colorectal cancer. More research is needed to confirm this possible link. Whether omega-3s affect the risk of other cancers is not clear. Clinical trials to examine this possibility are in progress.
Fish oil has the ability to treat Attention Deficit Hyperactivity Disorder (ADHD) due to its high concentration of fatty acids. For children suffering from hyperactivity, dyslexia, dyspraxia, inability to complete tasks, emotional instability, wavering attitude, poor coordination, short attention span, short-term memory weakness, low concentration, tendency to interrupt others, recklessness, hastiness, impetuosity, impulsiveness, low IQ, or learning disorders, fish oil is a proven remedy. Research conducted at the University of South Australia and CSIRO has shown that when children suffering from ADHD were given doses of fish oil and evening primrose capsules for 15 weeks, they showed significant improvements in their behavior. Since, human brain consists of about 60% fats, especially essential fatty acids such as omega-3 and omega-6, it helps to improve the functions of the brain.
Fish oil has been shown to have a direct electrophysiological effect on the myocardium. Initial experience with animal ischemia models demonstrated that the ventricular fibrillation threshold was increased in both animals fed or infused with omega-3 FA.23,24 This progressed to a demonstration, on a cellular and ion channel level, that omega-3 FA reduce both sodium currents and L-type calcium currents.25–29 It is hypothesized that during ischemia, a reduction in the sodium ion current protects hyperexcitable tissue, and a reduction in the calcium ion current reduces arrhythmogenic depolarizing currents.30
Fish oil is also used for diabetes, prediabetes, asthma, a movement and coordination disorder called dyspraxia, dyslexia, eczema, autism, obesity, weak bones (osteoporosis), rheumatoid arthritis (RA), osteoarthritis, psoriasis, an autoimmune disease called systemic lupus erythematosus (SLE), multiple sclerosis, HIV/AIDS, cystic fibrosis, gum disease, Lyme disease, sickle cell disease, and preventing weight loss caused by some cancer drugs.