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Comment & Response
February 2016

Proposed Guidelines for Future Vitamin D Studies

Author Affiliations
  • 1Division of Endocrinology, Department of Medicine, University of Kansas Medical Center, Kansas City
  • 2Division of Endocrinology and Metabolism, Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
  • 3Department of Clinical Diabetes, Endocrinology, and Metabolism, City of Hope National Medical Center, Duarte, California
JAMA Intern Med. 2016;176(2):280-281. doi:10.1001/jamainternmed.2015.7974

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.

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