Fig. 20
Predicted effects of co-supplementation on 25(OH)D and its metabolites with age. The predicted steady state values on day 200 of the concentration of extracellular 25(OH)D (D), extracellular 1,25(OH)2D (\(D_{a}\)), intracellular 25(OH)D (\(D_{i}\)), intracellular 1,25(OH)2D (\(D_{a_{i}}\)) and the VDR:1,25(OH)2D complex (\(V_{D_{a}}\)) with age, from solving Eqs. (3)–(23) with baseline parameters given in Tables 1, 2 and 3 and age functions given in Figs. 2, 3, 4 and 5. A daily intervention is administered from day 0 to day 200 to individuals aged 20-80 years for dosing regimens N, CVD, AVD, P, CCS and ACS with baseline values of vitamin D intake \(D^{0}=4.8\) and \(D^{1}=0.5\) nmol/L day−1 (no subscript on horizontal axis labels) and \(D^{0}=3.2\) and \(D^{1}=0.35\) nmol/L day−1 (subscript UK on horizontal axis labels).
