FIGURE 2.

Serum 25(OH)D₃ concentration compared with serum vitamin D₃ concentration at baseline and in the placebo group, i.e., in the unsupplemented state (open shapes), and after 1, 3, 6, or 12 mo of supplementation (closed shapes) in 2 pilot clinical trials of vitamin D₃ supplementation. Data are individual participant data (placebo, n = 11; 2000 IU/d, n = 19; 4000 IU/d, n = 7), all observations. SI conversion factors: vitamin D₃, 1 ng/mL = 2.6 nmol/L; 25(OH)D₃, 1 ng/mL = 2.5 nmol/L. BL, baseline; 25(OH)D₃, 25-hydroxyvitamin D₃.