To the Editor The trial by Hansen and colleagues1 was designed to study the effects of vitamin D supplementation on calcium absorption, bone mineral density (BMD), muscle function, and muscle mass. Serum 25-hydroxyvitamin D (25[OH]D) concentrations increased from 21 to 27 ng/mL (to convert to nanomoles per liter, multiply by 2.496) for low-dose vitamin D (LDD) and 42 ng/mL for high-dose vitamin D (HDD) by the end of the year-long trial. Total-hip BMD increased by 0.4% for LDD and 0.7% for HDD. Femoral neck BMD decreased by 0.1% for LDD and increased by 0.5% for HDD. The 95% CI ranged from 1.0% to 2.5%. Since only small effects were found, the results of this trial were interpreted as implying that 25(OH)D concentrations of 20 ng/mL are adequate.
Grant WB, Mascitelli L, Goldstein MR. Proposed Guidelines for Future Vitamin D Studies. JAMA Intern Med. 2016;176(2):279-280. doi:10.1001/jamainternmed.2015.7968