Calcium is the most abundant mineral in the human body. Calcium has long been recognized for its ability to keep bones healthy and strong. Most Americans believe they are getting enough calcium through their diet. However, more than 75% of Americans are calcium deficient according to a recent study published in the Journal of the American Medical Association. Calcium deficiency is mainly due the lack of calcium rich foods. Also, added ingredients in processed food such as phytate interfere with calcium absorption. When blood calcium levels drop too low, this vital mineral is borrowed from the bones. It is then returned to the bones if an adequate amount of calcium supplied through the diet. Choosing a good calcium supplement can be confusing at times. There are several different calcium preparations and hundreds of different formulations available. Most calcium supplements contain calcium citrate, calcium carbonate, or calcium phosphate. These calcium preparations differ in a number of ways, and recent research has shown that calcium bis-glycinate offers benefits that other calcium sources do not.