Your Guide to Taking Calcium Supplements

By Jodi Rigotti

When it comes to building strong bones and preventing osteoporosis, calcium is vital. Yet this essential mineral is not produced by the body and must therefore be obtained from outside sources. According to the National Osteoporosis Foundation (NOF), the best way to get enough of this bone-boosting mineral is via food. Among the best choices are yogurt, leafy greens and particular types of fish.

But if dietary restrictions are preventing you from eating high-calcium foods, or you simply can’t manage to meet your daily requirements (1,000 mg/day for women under 50, 1,200 mg/day for women 50 and older), a calcium supplement may be a good alternative. Roughly 43% of the U.S. population (including nearly 70% of older women) uses dietary supplements containing calcium, according to the National Institutes of Health.

Given so many calcium supplements on the market, how do you know which one to choose? First, it helps to understand more about calcium supplements, including their benefits and potential risks.

Calcium supplements and your heart

Recent studies have questioned the safety of calcium supplements. University of Auckland researchers looked at data from the Women’s Health Initiative Calcium/Vitamin D Supplementation Study—a seven-year trial involving about 36,000 postmenopausal women—and concluded that postmenopausal women who took calcium supplements had a 13%-22% greater risk of having a heart attack than women who didn’t take calcium supplements. The speculation is that calcium supplements may rapidly elevate blood calcium levels, contributing to artery disease.

More research is needed to confirm and clarify the results, but it’s still important to talk with your healthcare provider before you take a calcium supplement. Excessive calcium intake (which can happen when you introduce a supplement into an already calcium-rich diet) has also been linked to an increased risk of kidney stones.

Weighing your options

If your healthcare provider feels you could benefit from a calcium supplement, how do you know which one to choose? Calcium exists only in combination with other substances called salts (the calcium salt is called a compound). These compounds contain different amounts of elemental calcium, which is the actual amount of calcium in the supplement. The two main forms of calcium in supplements are calcium carbonate and calcium citrate. Keep in mind, too, that calcium is best absorbed when taken in amounts of 500 to 600 mg or less.

Calcium carbonate
Contains 40% elemental calcium by weight (1,000 mg of calcium carbonate provides 400 mg of calcium). Some studies suggest that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk.

Side effects: While most people digest calcium carbonate well, some may develop gastrointestinal discomfort.

Cost: The least expensive of the calcium supplements on the market.

Calcium citrate
Contains 21% elemental calcium by weight (1,000 mg of calcium citrate provides 210 mg of calcium). More of it must be taken for you to get the same amount of calcium as from calcium carbonate.

Side effects: Less likely to cause constipation and gas than calcium carbonate.

Cost: More expensive than calcium carbonate.

Other calcium supplements include calcium gluconate and calcium lactate but because they contain smaller percentages of elemental calcium, they’re generally not recommended as an option.

The bottom line

There are several good calcium supplements. The best, according to the NOF, is one that meets your needs, such as cost and the smallest number of side effects. Of course, the optimal way to meet your daily calcium needs is through a healthful diet.

Published September 2011
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