Natures Bounty Calcium Magnesium Zinc with Vitamin D3 contains 1000mg, 400mg, 25mg and 600IU amount per serving respectively. Calcium is the primary mineral responsible for strong bones. The body also uses Calcium for proper muscle contraction, nerve function and heart function. Vitamin D assists in Calcium absorption and maintaining a healthy immune system. Because the body cannot produce Calcium, a balanced diet, regular exercise, healthy lifestyle choices and adequate intake of Calcium and Vitamin D can play a role in maintaining optimal bone health. Adequate Calcium and Vitamin D throughout life, as part of a well-balanced diet, may reduce the risk of osteoporosis.