Total vitamin D intake and serum 25-hydroxyvitamin D by quintile. Individual total vitamin D intake (diet plus supplementation) and serum 25-hydroxyvitamin D (25(OH)D) levels at baseline. Serum 25(OH)D levels from 1,067 women identified as control subjects from a nested case-control study performed in the Women's Health Initiative trial evaluating calcium and vitamin D. Daily intakes of dietary and supplemental vitamin D were determined from self-report. The range of vitamin D intakes substantially overlaps in each 25(OH)D quintile. Line segments connect the mean vitamin D intake level in each quintile, which was 23.6, 38.5, 49.2, 60.9, and 81.9 nmol/l, respectively. Adapted with permission from Chlebowski and colleagues [42].