There are hundreds of different brands of calcium supplements and different forms of calcium. When we are talking about calcium intake, we are actually referring to the elemental calcium, not the compound calcium. What does this mean?
Elemental Calcium vs Calcium Compound
Calcium is absorbed into our body as ionized elemental calcium (Ca 2+). This means that we need to check the amount of elemental calcium the supplement contains rather than just the amount of calcium as a compound (ie calcium carbonate, calcium citrate etc). What is important on the label is the amount of elemental calcium, not just the calcium compound. For example, a calcium compound such as calcium carbonate has 40% of elemental calcium. If the bottle says each serving has 1000mg of calcium carbonate, it may only contains 400mg of elemental calcium. We can also check the label by looking for the RDA (Recommended Daily Amounts). If the bottle states a serving contains 40% of the RDA of calcium, then it contains 400mg of elemental calcium per serving (RDA for most individuals is 1000mg of calcium per day). Fortunately, elemental calcium is listed in the Supplement Facts panel, so consumers do not need to calculate the amount of calcium supplied by various forms of calcium supplements.
Different types of Calcium
Calcium may exist in different forms, each form may contain different amounts of elemental calcium. The two main forms of calcium in supplements are calcium carbonate and calcium citrate.
|Calcium carbonate(Ca2+: about 40% calcium by weight[i])||
|alcium citrate(Ca2+: about 20% by weight)||
|Calcium lactate(Ca2+: about 13% by weight)||
Other types of calcium supplements:
Oyster Shell Calcium: Due to environment pollution, some oyster shell calcium may contain lead. It’s up to the manufacture to strip away the lead from the oyster shell calcium as much as possible.
Ionized form: liquid or powder which can be dissolved in liquid is ideal.
[iii] Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.