Calcium, a mineral stored mainly in bones and teeth, helps maintain bone strength. Small amounts of calcium also circulate in the blood. People who don't consume many dairy products or people with low bone density may need more calcium than the diet can supply. Multivitamins normally don't supply enough calcium in these cases. Calcium supplements come in several different forms, each with different benefits and potential issues. Ask your doctor which calcium supplement you should take, as he may have a reason for suggesting a certain type for you.
Types
Calcium supplements may include different forms of calcium. Calcium carbonate, the least expensive and most widely used calcium supplement, composes 85 percent of all calcium supplements sold, according to GlaxoSmithKline's CalciumInfo website. Over-the-counter antacids, often taken as supplements, contain calcium carbonate. Calcium citrate, the more expensive form, also may need to be taken in larger quantities. Calcium gluconate and calcium lactate contain less calcium than other types of supplements, so much larger amounts may be needed to equal the same dose in the other two types. Sellers of coral calcium , a type of calcium carbonate, often make unsubstantiated claims about its benefits over other types of calcium. Coral calcium costs much more than other types of calcium.
Elemental Calcium
All calcium in supplements occurs as part of a compound, which is why different types of supplements have different names. Calcium carbonate, for example, binds calcium to carbonate. During digestion, the compound breaks apart and the calcium, called elemental calcium, can be absorbed in the small intestine. Elemental calcium is found in differing amounts in different types of supplements. Calcium carbonate contains 40 percent elemental calcium, while calcium citrate contains 21 percent elemental calcium. So 1,000mg of calcium carbonate supplies 400mg of elemental calcium, while 1,000mg of calcium citrate contains 210mg.
Doses
Recommended doses of calcium vary depending on age. Adults between the ages of 19 and 50 should take 1,000mg per day. Women over 50 and men over 71 require 1,200mg per day. The intestines will only absorb around 500mg of elemental calcium at a time, so break up daily doses for best absorption.
Absorption
While the amount of elemental calcium in supplements is important, other factors also affect absorption. Calcium citrate absorbs better than calcium carbonate, because citrate is acidic. Acid breaks down the calcium compound. Calcium carbonate requires stomach acid to break it down and absorbs best when taken with food. Because stomach acid levels generally decrease as people age, people over age 50 may absorb calcium citrate better than calcium carbonate, the Office of Dietary Supplements reports.
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