Effects of vitamin D supplementation on bone density in healthy children: systematic review and meta-analysis

Systematic review and meta-analysis of randomized placebo-controlled trials in healthy children and adolescents from infancy to late adolescence. Across the active vitamin D arms, 541 participants were included in 6 studies, with baseline vitamin D status ranging from deficient to sufficient and pubertal status varying from prepubertal to mixed.

Oral cholecalciferol (vitamin D3) supplementation was tested across 6 randomized placebo-controlled trials, with doses ranging from 132 IU/day to 400 IU/day, 1400 IU/week, or 14,000 IU/week, for 1 to 2 years. Placebo was the comparator; in two studies, calcium was also given to both groups as a background cointervention.

Vitamin D supplementation did not meaningfully improve bone density overall in healthy children and adolescents, especially when baseline vitamin D levels were normal. Pooled effects were small and not statistically significant for hip bone mineral density (SMD 0.06, 95% CI -0.18 to 0.29), lumbar spine bone mineral density (SMD 0.15, 95% CI -0.01 to 0.31; P=0.07), total body bone mineral content (SMD 0.10, 95% CI -0.06 to 0.26), and forearm bone mineral density (SMD 0.04, 95% CI -0.36 to 0.45). In children with low baseline vitamin D, subgroup analyses suggested possible clinically useful gains, particularly at the lumbar spine and for total body bone mineral content. These low-vitamin-D signals are promising but need confirmation in additional trials.

Only 6 trials were available, and they differed in age, pubertal status, baseline vitamin D level, dose, duration, and skeletal sites measured, limiting comparability. Several outcomes were based on subgroup analyses, so the apparent benefit in children with low baseline vitamin D remains exploratory. Adverse event reporting was limited and included isolated events such as skin allergy and hypercalcemia, which do not support a clear safety signal either way.