Natural Factors Calcium & Magnesium 2:1 Plus Vitamin D3 - Essential for the development and maintenance of healthy bones and teeth, everyone should be sure to maintain adequate levels of Calcium - especially women who are prone to osteoporosis. Calcium is also vital for proper muscle development and functionality, can help blood clotting, may assist in lowering blood pressure and helps activate many enzymes. When mixed with Magnesium, Calcium's ability to do its job is greatly enhanced.