THE CALCIUM CONTROVERSY REVISITED - IMPLICATIONS OF NEW DATA

Objective: To review and synthesise recent literature relating to the skeletal effects of dietary calcium supplementation. Date sources: Six recent randomised controlled clinical trials are reviewed together wi th other relevant clinical and physiological studies. Conclusions: Rec ent controlled clinical trials of the effect of dietary calcium supple mentation in postmenopausal women have supported the conclusion that i ncreasing calcium intake can slow bone loss at appendicular and axial skeletal sites. Supplementation may be more effective in those with a low calcium intake or when combined with an exercise regimen in those with low bone mass, and was more effective in women further from the m enopause. Calcium has its effect by reducing bone resorption. The effe ct of dietary calcium on bone is due to the absorbed fraction which is influenced negatively by other dietary factors such as dietary fibre and positively by the circulating concentration of the active form of vitamin D, calcitriol. To improve the efficacy of calcium supplements it will be necessary to optimise absorption. Nevertheless, in the ligh t of these recent trials it would be reasonable to consider increasing the Australian recommended dietary intake for postmenopausal women to 1500 mg calcium per day.