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

Background: Children in northern latitudes are at high risk of vitamin D deficiency during winter because of negligible dermal vitamin D-3 production. However, to our knowledge, the dietary requirement for maintaining the nutritional adequacy of vitamin D in young children has not been investigated. Objective: We aimed to establish the distribution of vitamin D intakes required to maintain winter serum 25-hydroxyvitamin D [25(OH)D] concentrations above the proposed cutoffs (25, 30, 40, and 50 nmol/L) in white Danish children aged 4-8 y living at 55 degrees N. Design: In a double-blind, randomized, controlled trial 119 children (mean age: 6.7 y) were assigned to 0 (placebo), 10, or 20 mu g vitamin D-3/d supplementation for 20 wk. We measured anthropometry, dietary vitamin D, and serum 25(OH)D with liquid chromatography tandem mass spectrometry at baseline and endpoint. Results: The mean +/- SD baseline serum 25(OH)D was 56.7 +/- 123 nmol/L (range: 28.7-101.4 nmol/L). Serum 25(OH)D increased by a mean SE of 4.9 +/- 1.3 and 17.7 +/- 1.8 nmol/L in the groups receiving 10 and 20 mu g vitamin D3/d, respectively, and decreased by 24.1 +/- 1.2 nmol/L in the placebo group (P < 0.001). A nonlinear model of serum 25(OH)D as a function of total vitamin D intake (diet and supplements) was lit to the data. The estimated vitamin D intakes required to maintain winter serum 25(OH)D >30 (avoiding deficiency) and >50 nmol/L (ensuring adequacy) in 97.5% of participants were 8.3 and 19.5 mu g/d, respectively, and 4.4 mu g/d was required to maintain serum 25(OH)D >40 nmol/L in 50% of participants. Conclusions: Vitamin D intakes between 8 and 20 mu g/d are required by white 4- to 8-y-olds during winter in northern latitudes to maintain serum 25(OH)D >30-50 nmol/L depending on chosen serum 25(OH)D threshold.