Cod Liver Oil is a natural source of Vitamins A and D, which help maintain bones and a healthy immune system. Vitamin A also assists in many other functions, such as eyesight and skin maintenance.Cod Liver Oil is a natural source of vitamin D and A and assists in the absorbtion and use of calcium and phosphorus.  Working together, Vitamin A and D help to support bone growth and density and a strong immune system. Viatmins A and D are important for the development of bones,  as well as the maintenance of teeth, skin, and eyesight.