Estimation of the dietary requirement for vitamin D in white children aged 4-8 y: a randomized, controlled, dose-response trial.

Randomized, double-blind, placebo-controlled dose-response trial in healthy white Danish or European children aged 4 to 8 years living at northern latitude in Denmark during winter. The study evaluated whether daily vitamin D3 supplementation maintained serum 25(OH)D concentrations above prespecified thresholds.

Vitamin D3 (Minisun tablets) was given orally once daily for 20 weeks at 10 mg/day or 20 mg/day in a randomized, double-blind, placebo-controlled dose-response trial. The active regimens were compared with placebo.

Vitamin D3 supplementation increased winter serum 25(OH)D in a clear dose-response manner and lowered PTH, with no safety signal. Endpoint serum 25(OH)D was 31.1 ± 7.5 nmol/L with placebo, 61.8 ± 10.6 nmol/L with 10 mg/day, and 75.8 ± 11.5 nmol/L with 20 mg/day (p<0.0001). Endpoint plasma PTH was 2.52 ± 1.23 pmol/L with placebo, 2.20 ± 0.73 pmol/L with 10 mg/day, and 1.91 ± 0.85 pmol/L with 20 mg/day (p<0.0001). Serum calcium did not differ meaningfully between groups at endpoint (p=0.45), and no serious adverse events or supplementation-related adverse events were reported. The authors concluded that winter intakes of about 8 to 20 mg/day are needed to maintain 25(OH)D above 30 to 50 nmol/L in this population.

Arm-specific sample sizes and detailed arm-level demographics were not reported in the extraction. The trial was short term, restricted to healthy white children in Denmark during winter, and therefore may not generalize to other ages, ethnicities, or seasons. The intervention estimate is based on biomarker outcomes rather than clinical endpoints.