The University of Arizona Cooperative Extension has an excellent review of calcium supplements. It is well written, thorough, and concise — just 4 pages long. The part I like best is the discussion of the difference between elemental and total calcium.
“The calcium in a compound is called elemental calcium. During digestion, the calcium compound dissolves and the elemental calcium becomes available to be absorbed into the blood. If a tablet contains 500 mg of calcium carbonate, it contains only 200 mg of elemental calcium. This is because only 40% of the calcium compound is elemental calcium. The other 60%, or 300 mg, would be from the carbonate ingredient. Most calcium supplements list the elemental calcium content on the label.”
If it’s not clearly marked on the front of the label, look at the “Nutrition Facts” label on the back of the container. Then, check the “serving size” to learn how many tablets must be taken to get the elemental calcium dose.
The same is true for iron, magnesium, selenium, and other mineral supplements.
John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at www.Vicus.com, a complementary and alternative medicine website.