essential nutrient Calcium WebMD WebMD, Calcium WebMD, October 31, 2016 calcium https://www.webmd.com/diet/supplement-guide-calcium homeostasis mineral essential nutrient http://www.webmd.com/diet/supplement-guide-calcium#1 Calcium WebMD, October 31, 2016 key player https://www.webmd.com/diet/supplement-guide-calcium#1 bone growth calcium