Choosing a calcium supplement

The key factor to consider when buying calcium supplements is the amount of elemental calcium they contain. The term elemental calcium refers to the amount of calcium in a supplement that's available for your body to absorb. Most calcium supplements list the amount of elemental calcium on the label. But some brands list only the total weight — in milligrams (mg) — of each tablet. This is the weight of the calcium, plus whatever it's bound to — such as carbonate, citrate, lactate or gluconate.

The simplest way to determine how much elemental calcium is in a supplement is to look at the Nutrition Facts label. For calcium, the % Daily Value (DV) is based on 1,000 mg of elemental calcium, so every 10% in the Daily Value column represents 100 mg of elemental calcium (0.10 x 1,000 mg = 100 mg). For example, if a calcium supplement has 60% Daily Value, it contains 600 mg of elemental calcium (0.60 x 1,000 mg = 600 mg). Also, it's important to note the serving size — the number of tablets you must take to get the % DV listed on the label.

When choosing a calcium supplement, check the label for the abbreviation USP. The best supplements meet the voluntary standards of the U.S. Pharmacopeia (USP) for quality, purity and tablet disintegration or dissolution. Generic brands of calcium supplements are often cheaper than name brands. However, they may not meet voluntary standards for tablet disintegration. In other words, they may dissolve more slowly, which decreases their effectiveness.

Avoid calcium supplements that contain bone meal or dolomite. These products may also contain toxic substances, such as lead, mercury and arsenic. Also, don't bother with chelated calcium tablets. They're more expensive and have no advantage over other types of calcium.