Response of Vitamin D Concentration to Vitamin D3 Administration in Older Adults without Sun Exposure: A Randomized Double-Blind Trial

Objectives To determine the dose-response relationship between 25-hydroxyvitamin D (25(OH)D) and supplemental vitamin D3 in elderly nursing home residents. Design Randomized double-blind investigation. Setting Nursing home. Participants Of 81 women (n = 51) and men (n = 30) (mean age 87.4 ± 8) enrolled, 72 completed the study. Intervention Sixteen weeks of oral vitamin D3 at 800, 2,000, or 4,000 IU/d or 50,000 IU/wk. Measurements The main outcome was 25(OH)D concentrations (tandem mass spectrometry) after 16 weeks. Free 25(OH)D and intact parathyroid hormone (iPTH) were also analyzed. Safety monitoring of calcium and estimated glomerular filtration rate was performed, and adherence and clinical status were measured. Results 25(OH)D concentrations increased with dose (P