Mycrocrystalline 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 highly absorbable Calcium and Phosphorus, which are the major mineral components of bone. NOW® Bone Strength™ is a comprehensive bone support product providing 4 g (4,000 mg) of MCHA. It also contains Magnesium and Trace Minerals, as well as Vitamins C, D and K to aid in the synthesis and maintenance of bone tissue.