Healthy pH Balance Important for Bone Health Magnesium & Vitamin D for Bone Metabolism* NOW Coral Calcium Plus contains an alkaline form of Calcium that can help to support a healthy serum pH. In addition, Coral Calcium containsa number of trace minerals that are important for bone health, as well as for optimal enzymatic activity. NOW Coral Calcium is not harvested from living coral reefs or even from the ocean environment, but from above-ground sources in Okinawa in an ecologically friendly manner. In this Coral Calcium Plus formula, Magnesium and Vitamin D have been added because of their essential role in bone metabolism.