Calcium is an important macromineral required for a number of physiological processes such as bone formation, pH regulation, muscle contraction and nerve condition. Increasingly calcium is also being seen to play a role in blood pressure regulation and in weight control. Supplementation of calcium is an effective way to provide optimal quantities of this important mineral, and calcium supplements have been popular since early research showed a possible role for supplemental calcium in the prevention of osteoporosis in women. However, calcium supplements vary in their bioavailability, and controversy exists as to the most absorbable form of calcium currently available in supplemental form. Generally, calcium bonded to organic chemicals is more readily absorbed that inorganic forms of the mineral. This is likely related to the ability of the organic moiety to be actively transported across the gut lining.
Researchers have extensively investigated the absorbability of different forms of calcium. Many studies agree that organically bound calcium is more absorbable than inorganic forms of the mineral. For example, one study1 investigated the absorption from calcium carbonate versus calcium bound to malic and citric acid in a randomised double-blind study using healthy adolescent subjects. The results showed that calcium in the organic bound form was absorbed at 36.2 % compared to 26.4 % for calcium carbonate. Therefore organically bound forms of calcium may be superior to non-organically bound forms. However, inorganic forms of the mineral tend to be cheaper, and this should be taken into account when purchasing supplements. If calcium carbonate or other inorganic forms of the mineral are used, larger intakes would be required to reach the same level of absorption as organically bound forms of the mineral.
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