To the Editor The recent article by Hansen et al1 described a randomized clinical trial on the treatment of vitamin D insufficiency in postmenopausal women. This is a topic of great interest to us, and we would like to express some serious concerns regarding the conclusions drawn by Hansen et al.
The aim of this study was to compare the effect of placebo, low-dose cholecalciferol (800 IU daily), and high-dose cholecalciferol (50 000 IU twice monthly) on total fractional calcium absorption (TFCA), bone density, and muscle outcomes. Although this study had the adequate power to detect changes in TFCA, the primary outcome, there is lack of discussion regarding the power of this study to detect the differences in muscle outcomes and bone mineral density. Based on the reported standard deviation of muscle outcomes and bone mineral density, the current study is not equipped with adequate power to detect the proposed difference, if any. Thus, it is premature for the authors to conclude that high-dose cholecalciferol therapy failed to improve bone density and muscle outcomes.
Karnchanasorn R, Ou H, Chiu KC. Proposed Guidelines for Future Vitamin D Studies. JAMA Intern Med. 2016;176(2):280-281. doi:10.1001/jamainternmed.2015.7974