Bone meal is a natural source of Calcium Phosphate, a composition of Calcium and Phosphorus known as hydroxyapatite. Hydroxyapatite, found in teeth and bones, confers rigidity to these structures and is well absorbed from the digestive tract. Phosphorus is necessary for the production of bone tissue and plays an integral role in the maintenance of the body's acid-base balance. NOW Bone Calcium has been enhanced with Vitamin D, as well as complementary minerals, such as Magnesium, Zinc, Copper, Manganese, and Boron, that work with Calcium to support healthy bone metabolism.* NOW Bone Calcium is naturally derived from cattle raised in Australia. It is sterilized and tested for heavy metals such as lead and aluminum to assure the lowest levels possible.