The most common forms of EDTA are calcium and sodium chelates, which are available in both USP (United States pharmacopoeia) and FCC (food chemical codex) forms. Magnesium EDTA, however, is not commercially available in either of these standards.
Even after 68 years of research into EDTA chemistry, the calcium disodium form continues to come out on top in regards to lowest toxicity, longest history of safe use in humans and other animals, and as the safest and most effective oral chelator.
Many people raises the question that since chelation removes excess blood calcium that contributes to artery-clogging plaque, why include calcium in a product designed to remove calcium? Well—other than the obvious issues relating to 38 years of safe and beneficial oral chelation—calcium disodium EDTA works on calcified deposits, not calcium directly.
This calcification is a conglomeration of calcium and heavy metals and is not soluble or metabolized due, in part, to its heavy metal content. As calcium disodium EDTA encounters these calcifications, it chelates the heavy metal portion of these deposits allowing the release of the calcium for use in normal metabolic functions.