Effect of low‐dose calcium supplements on bone loss in perimenopausal and postmenopausal Asian women: A randomized controlled trial

This was a randomized, double-blind, placebo-controlled trial in healthy Japanese women aged 50–75 years who were perimenopausal or postmenopausal and had habitually low calcium intake. For the 500 mg/day calcium group, 139 participants were analyzed at follow-up; for the 250 mg/day calcium group, 137 participants were analyzed at follow-up.

The active intervention was oral calcium carbonate given daily with meals for 2 years. The 500 mg/day group received five tablets totaling 500 mg elemental calcium per day, and the 250 mg/day group received five tablets totaling 250 mg elemental calcium per day; both were compared with placebo.

Calcium 500 mg/day slowed lumbar spine bone loss over 2 years, while the 250 mg/day dose showed less consistent benefit. Intention-to-treat lumbar spine BMD change was −0.029 g/cm2 (−3.0%) with 500 mg/day, −0.034 g/cm2 (−3.7%) with 250 mg/day, and −0.040 g/cm2 (−4.2%) with placebo; the 500 mg/day group differed from placebo (p = 0.027), but the 250 mg/day group did not (p = 0.321). Femoral neck BMD change was not significantly different from placebo for either dose: −0.028 g/cm2 (−3.9%) for 500 mg/day, p = 0.156, and −0.037 g/cm2 (−5.3%) for 250 mg/day, p = 0.565. The 500 mg/day and 250 mg/day groups also differed from each other for spine outcomes (p = 0.024).

The trial was limited to Japanese women with low habitual calcium intake, which narrows generalizability. The 250 mg/day dose did not show a clear benefit, and femoral neck outcomes were inconclusive for both doses. Interpretation is also constrained by the modest absolute BMD changes and the 2-year follow-up duration.