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Medical Author:

Coburn Hobar, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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While experts recommend getting as much calcium and other nutrients as possible from foods instead of from supplements, it may be difficult to get all the calcium needed from diet alone. A calcium supplement may be taken to help make up the difference.

Calcium supplements come in a variety of different forms, including compounds such as calcium citrate (Citracal or Solgar), calcium lactate, and calcium gluconate. The actual amount of calcium, called elemental calcium, varies in each supplement. Chelated forms of calcium, such as in the compounds just listed, are more easily absorbed by the body than other forms of calcium. However, calcium carbonate (Os-Cal or Tums), while not as easily absorbed, contains the highest amount of elemental calcium.

Be sure to examine the labels of supplements to see how much elemental calcium they have and what the serving sizes are. In some cases, the serving size is more than one tablet.

Calcium carbonate and calcium citrate are the most commonly used calcium supplements, particularly because they contain more calcium per tablet and are less expensive per milligram of calcium than other supplements. Calcium carbonate supplies more elemental calcium per tablet than other forms and is therefore usually the best value; however, it is best to take this kind of calcium compound with food because stomach acid is needed to dissolve it. Calcium citrate has less elemental calcium in it, so more of it will need to be taken, but it is absorbed more easily than calcium carbonate.

When taking a supplement, a few other things should be considered.

• More isn't always better; the recommended daily dose should not be exceeded because exceeding the dose increases the risk of side effects.
• A doctor or pharmacist knows whether a calcium supplement will interact with any prescription medications also being taken. For example, calcium chews, such as Viactiv, contain calcium and vitamin D but also contain vitamin K and should not be taken by individuals treated with anticoagulants, such as warfarin (Coumadin).
• To retain maximum supplement absorption, just as with dietary calcium, take only about 500 mg or less at one time.

When purchasing a calcium supplement, check with the pharmacist or doctor. Since the manufactures of these dietary supplements are not regulated as prescription medications, look for a reputable brand name or a company that advertises "quality control." This ensures that the advertised amount of elemental calcium per tablet is correct.

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