I often get questions about what form of calcium is best to maintain strong bones. When it comes to calcium supplements, for most people, calcium carbonate—the most popular and inexpensive kind—will work just fine.
Most of the studies on calcium for bone health have been on calcium carbonate and they reveal that it is as bioavailable (easily absorbed) as the calcium in milk. However, depending on how calcium carbonate tablets are manufactured, they may not be well-absorbed by people deficient in stomach acid—a problem for some people over age 50.
To test their absorbency, place a calcium carbonate tablet in a half-cup of vinegar and stir occasionally. After half an hour, there should be no undissolved chunks of the tablet in the bottom of the glass. Taking calcium carbonate with food greatly enhances its absorption, as does supplementing with betaine HCl, a natural source of hydrochloric acid. (Quality supplements often include betaine HCl along with calcium.)
Calcium citrate is a more expensive option for bone health. Several studies have shown that calcium citrate is approximately 25 percent better absorbed than other forms of calcium. However, people’s ability to absorb different compounds vary, so your best bet for strong bones may be a calcium supplement that contains a variety of calcium sources, including carbonate and citrate, as well as other chelates such as ascorbate, aspartate, or malate.
When it comes to maintaining strong bones, the only forms of calcium I specifically do not recommend are bone meal, dolomite, and oyster shell calcium, as these forms can contain high levels of lead.
Magnesium Also Important for Strong Bones
I shudder to think of how many women take calcium pills day after day, hoping to maintain strong bones and prevent osteoporosis, without knowing that calcium should be taken with magnesium to be optimally absorbed into bones.
Magnesium for bone health is as important as calcium for bone health, and these two minerals compete for absorption in the body. So be sure your calcium supplement is balanced with magnesium in a 2:1 ratio (e.g., if you take 1,000 mg of calcium, combine it with 500 mg of magnesium).