High-dose oral vitamin D3 supplementation in the elderly

Summary  Daily dosing with vitamin D often fails to achieve optimal outcomes, and it is uncertain what the target level of 25-hydroxyvitamin D should be. This study found that large loading doses of vitamin D₃ rapidly and safely normalize 25OHD levels, and that monthly dosing is similarly effective after 3–5 months. With baseline 25OHD > 50 nmol/L, vitamin D supplementation does not reduce PTH levels. Introduction  There is concern that vitamin D supplementation doses are frequently inadequate, and that compliance with daily medication is likely to be suboptimal. Methods  This randomized double-blind trial compares responses to three high-dose vitamin D₃ regimens and estimates optimal 25-hydroxyvitamin D (25OHD) levels, from changes in parathyroid hormone (PTH), and procollagen type I amino-terminal propeptide (P1NP) in relation to baseline 25OHD. Sixty-three elderly participants were randomized to three regimens of vitamin D supplementation: a 500,000-IU loading dose; the loading dose plus 50,000 IU/month; or 50,000 IU/month. Results  The Loading and Loading + Monthly groups showed increases in 25OHD of 58 ± 28 nmol/L from baseline to 1 month. Thereafter, levels gradually declined to plateaus of 69 ± 5 nmol/L and 91 ± 4 nmol/l, respectively. In the Monthly group, 25OHD reached a plateau of ~80 ± 20 nmol/L at 3–5 months. There were no changes in serum calcium concentrations. PTH and P1NP were only suppressed by vitamin D treatment in those with baseline 25OHD levels <50 and <30 nmol/L, respectively. Conclusions  Large loading doses of vitamin D₃ rapidly and safely normalize 25OHD levels in the frail elderly. Monthly dosing is similarly effective and safe, but takes 3–5 months for plateau 25OHD levels to be reached.