Increased Vitamin D intake differentiated according to skin color is needed to meet requirements in young Swedish children during winter: A double-blind randomized clinical trial

Background: Dark skin and low exposure to sunlight increase the risk of Vitamin D insufficiency in children. Objective: The aim of the study was to evaluate the amount of Vitamin D needed to ascertain that most children > 4 y of age attain sufficient serum25-hydroxyVitamin D [S-25(OH)D; i.e.,≥50 nmol/L] during winter regardless of latitude and skin color. Design: In a longitudinal, double-blind, randomized, food-based intervention study, 5- to 7-y-old children from northern (638N) and southern (55°N) Sweden with fair (n = 108) and dark (n = 98) skin were included. Children, stratified by skin color by using Fitzpatrick's definition, were randomly assigned to receive milk-based Vitamin D₃ supplements that provided 2 (placebo), 10, or 25 μg/d during 3 winter months. Results: Mean daily Vitamin D intake increased from 6 to 17 mg and 26 mg in the intervention groups supplemented with 10 and 25 mg, respectively. In the intention-to-treat analysis, 90.2% (95% CI: 81.1%, 99.3%) of fair-skinned children randomly assigned to supplementation of 10 mg/d attained sufficient concentrations, whereas 25 mg/d was needed in dark-skinned children to reach sufficiency in 95.1% (95% CI: 88.5%, 100%). In children adherent to the study product, 97% (95% CI: 91.3%, 100%) and 87.9% (95% CI: 76.8%, 99%) of fair- and dark-skinned children, respectively, achieved sufficient concentrations if supplemented with 10 μg/d. By using 95% prediction intervals for 30 and 50 nmol S-25(OH)D/L, intakes of 6 and 20 μg/d are required in fair-skinned children, whereas 14 and 28 μg/d are required in children with dark skin. Conclusion: Children with fair and dark skin require Vitamin D intakes of 20 and 28 μg/d, respectively, to maintain S-25(OH)D ≥50 nmol/L, whereas intakes of 6 and 14 mg/d, respectively, are required to maintain concentrations ≥30 nmol/L during winter. This trial was registered at clinicaltrials.gov as NCT01741324.