Cod Liver Oil was invented for rickets, when the first machines where invented. The reason? the skies where filed with so much pollution that it clouded out sunlight. They added vitamin D for that reason. If you take too much vitamin A, you can become toxic, thereby lessening the wanted effect of improving health. I take krill oil, in a liquid capsule form, contains all 3 omegas, and no fishy burps. Vitamin D3, in liquid capsule form 4000 IU daily. D3 is a form more easily assimilated by the body. The omegas have a possitive influence on cognetive health, circulation, cholesterol,moods, hormones, and the heart. D3 is a necessary nutrient involved in all aspects of health, including the muscles, nerves, and bones. Yes, I have seen a possitive aspect achieved from taking these nutrients. I sleep better, my muscles don't spasm as much, my bones are stronger, and the hot flashes have diminished, as well.