The role of Vitamin D in helping to maintain bone density and strength is clear. It is required for the process of moving calcium through the intestinal wall into the bloodstream. 

Even through the human body can manufacture Vitamin D under ideal circumstances, there is strong evidence that much of the American population suffers from a deficiency of the nutrient.  This means that supplementation may be important. The cholecaflciferol (D3) is a natural, highly bioavailable form of Vitamin D derived from lanolin.