<qa>  What is the metabolite of vitamin D3?The investigators are intending to perform a clinical study in healthy subjects on the pharmacokinetics of different doses of Hy.D Calcifediol compared to vitamin D3 cholecalciferol in order to gain insight into the dose response relationship and to assess kinetic differences including the steady state. The metabolites 1,25OH2D, 24,25OH2D will be assessed throughout the study to assess the metabolism of vitamin D vs. 25OHD. Vitamin D3 will be measured throughout the study to assess compliance with the restriction of exogenous vitamin D supplementation. 