Biochemical responses to vitamin D3 supplementation of endocrine outpatients during one year. Open bars indicate pre-supplementation data; boxes with intermediate shading indicate data at 2–6 months; darkest boxes, indicate data after >6 months of vitamin D. By the second visit after starting vitamin D, plasma 25(OH)D was higher in those taking 100 mcg/day than in those taking 15 mcg/day (values marked b differ significantly from the group's baseline values marked a, p < 0.001, by paired t-test). 25(OH)D values marked b differ significantly from each other, conventional Students t-test, p = 0.006). PTH values marked c differ significantly from the group's baseline value, p = 0.003; PTH values marked d differ significantly from the group's baseline value, p = 0.013.
Vieth et al. Nutrition Journal 2004 3:8 doi:10.1186/1475-2891-3-8