Calcium supplementation for improving bone mineral density in children.

Systematic review and meta-analysis of 19 randomized trials in healthy children and adolescents under 18 years without medical conditions affecting bone metabolism. Across the review, 1367 participants were randomized to calcium supplementation and 1426 to placebo, with trials enrolling prepubertal and pubertal/post-pubertal participants from diverse ethnic backgrounds.

Calcium supplementation was tested in multiple forms, including calcium carbonate, calcium citrate malate, calcium phosphate, milk extract, and milk minerals, at doses ranging from 300 mg/day to 1200 mg/day, usually given orally for the trial duration versus placebo. Regimens varied across studies, including daily dosing and one trial using calcium 1000 mg/day 5 days per week.

Calcium supplementation had little overall effect on bone mineral density in healthy children. A small, statistically modest benefit was seen at the upper limb, and that effect persisted after supplementation stopped, but it was unlikely to translate into a clinically meaningful reduction in fracture risk. Many other bone sites and outcomes showed no statistically significant difference, and the review concluded that the evidence does not support calcium supplementation as a public health intervention for healthy children. The findings should not be extrapolated to children with medical conditions that affect bone metabolism.

The included trials were heterogeneous in calcium form, dose, duration, age, pubertal status, baseline calcium intake, ethnicity, and outcome site, which limits comparability. Many endpoints were nonsignificant and fracture outcomes were not established as a clinical benefit. Generalizability is limited to healthy children and adolescents, not to children with bone-metabolism disorders.