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Comment & Response
February 2016

Proposed Guidelines for Future Vitamin D Studies—Reply

Author Affiliations
  • 1Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison
JAMA Intern Med. 2016;176(2):281-282. doi:10.1001/jamainternmed.2015.7983

In Reply We thank our colleagues for expressing interest in our study.1 Grant et al felt that we would have detected benefits of low-dose vitamin D had we recruited subjects with lower 25- hydroxyvitamin D (25[OH]D) levels. However, we purposefully excluded subjects with vitamin D deficiency, for whom benefits of therapy are established.2 Instead, we designed our study to directly address controversy regarding the highest 25(OH)D level needed to experience benefits of vitamin D as stated in our introduction,1 with some experts recommending levels 30 ng/mL or greater (to convert to nanomoles per liter, multiply by 2.496) and others recommending levels 20 ng/mL or greater.2 Therefore, we recruited subjects with levels less than 30 ng/mL and randomized one-third to a high-dose vitamin D regimen that kept their 25(OH)D higher than 30 ng/mL. We anticipated that most subjects in the low-dose and placebo arms would have levels less than 30 ng/mL during the trial and enhanced that likelihood by dispensing sunscreen to all subjects.

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