Most calcium supplements are made from either calcium carbonate or calcium citrate. One study has found that calcium citrate is up to 27% more absorbable than calcium carbonate. Also, the carbonate form requires sufficient stomach acid for proper absorption. Because of its superior absorption rate and the fact that stomach acid levels are not critical, calcium citrate supplements are considered the superior choice—especially for older adults.

At the Center for Mineral Metabolism and Clinical Research in Dallas, researchers studied a group of women for a period of two years to test the effectiveness of calcium citrate on bone density. In this trial, 63 postmenopausal women were given either a placebo or 800 mg of calcium citrate daily. While the placebo group lost bone density during the trial, the calcium citrate group did not. Furthermore, the calcium citrate provided long-term protective effects for bone density. The researchers concluded that calcium citrate supplementation averted bone loss and stabilized bone density.

Researchers at Boston University wanted to know if calcium and vitamin D supplementation, known to help slow bone loss, could also help slow tooth loss. They studied 145 healthy seniors in a placebo-controlled study for five years. During the first three years, the people supplemented with calcium and vitamin D, while in the last two years, they received no calcium and vitamin D. The results showed the calcium/vitamin D group had less tooth loss than the placebo group. Researchers concluded that calcium and vitamin D supplementation did have beneficial effect on tooth retention.

Sources: Am J Ther 1999 Nov;6(6):303-11; Am J Med 2001 Oct 15;111(6)452-6