Microcrystalline Hydroxyapatite (MCHA) is a natural compound that makes up the crystalline matrix of bone and teeth, and is the substance that gives them their rigidity. MCHA is a source of highly absorbable Calcium and Phosphorus, which are the major mineral components of bone. NOW Bone Strength is a comprehensive bone support product with MCHA. It also has Magnesium and other important minerals, as well as Vitamins C, D and K to aid in the synthesis and maintenance of bone tissue.* NOW Microcrystalline Hydroxyapatite (MCHA) is derived exclusively from Australian cattle.