Dr. Joel Wallach, BS, DVM, ND
Bone Density Needs Calcium Supplementation Dr. Joel Wallach
If you've done any research at all into mineral supplements, you are aware that calcium comes in many different forms. Why such an array of options - and which is best for you?
Calcium comes in different forms because, alone, it is an unstable mineral.
In nature, it is almost always found as a calcium salt, attached by a chemical bond to another mineral. In calcium carbonate, the stabilizing mineral is carbon. Calcium bound to citric acid is called calcium citrate. Other calcium compounds include calcium lactate (found in milk) and calcium hydroxyapatite (from the bones of cattle).
When you swallow a calcium tablet, the acid in your stomach has to break the calcium compound down before the elemental calcium can be absorbed into your bloodstream. If your stomach acid is normal, your body may actually absorb 22% of the elemental calcium in your calcium carbonate supplement. If your stomach acid is low, absorption may be as little as 4%.
Coral calcium, which has been advertised as a new calcium form, is actually just calcium carbonate, with a fancy new name (and a price tag to match). Despite some fairly extravagant claims, it does not really do anything other calcium's cannot do. Calcium citrate is easier than calcium carbonate for your system to absorb. But it has a drawback: it contains only about 10% elemental calcium. That's why calcium citrate tablets are so big and hard to swallow.