Datta P, et al. - Among 19 Danish participants, researchers investigated the inter-individual variation in 25(OH)D₃ increase (Δ25(OH)D₃) after vitamin D₃ supplementation and compared it with the UVB irradiation response. Participants were administered 85 μg vitamin D₃ (cholecalciferol) daily for nine weeks and were made to undergo regular serum 25(OH)D₃ measurements. Three years earlier, these participants had participated in a 9-week controlled UVB study. The analysis revealed comparable inter-individual variation in the two interventions and it had no common demographic but a partly common genetic background.