Calcium Plus Vitamin D [Structural] supplies nutrients required for both the structural and nervous systems. Combined with other trace minerals needed by the body, NSP Calcium helps replenish bone tissue that is constantly being replaced. Calcium comprises half of all the minerals in the body. This formula also contains phosphorus, the second most abundant mineral in the body. It works with calcium. This formulation provides calcium and phosphorus at a 2:l ratio. Magnesium is also added in the same 2:1 ratio with calcium. Without these important ratios, the body begins to lose one or more minerals before it can utilize them. Calcium is needed by the immune system and is critical to muscle contractions. Phosphorus works synergistically with B vitamins to help maintain a proper fluid balance in the body. Vitamin D is added to help calcium do its job. At least 400 IU of vitamin D is needed on a daily basis, especially for those not getting enough sunshine (D is the "sunshine vitamin"). These nutrients come in a base of alfalfa herb and contain no sugar, starch, artificial coloring or flavoring.