Elemental calcium is a "meaningless" term which can be replaced by the word calcium. It only occurs in the world of dietary supplements. "Pure" metallic calcium is never ingested so in a real sense elemental calcium does not have a unique absorbability - it all depends on which calcium containing compound you are measuring. Another factor to consider is that high concentrations of calcium in the diet inhibit its takeup. Most calcium supplements are therefore better taken on a "little and often" basis. For this reason treatments used for the prevention of osteoporosis are frequently administered in the form of a chewing gum.