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Proposed Guidelines for Future Vitamin D Studies

Proposed Guidelines for Future Vitamin D Studies 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. This study further demonstrated that low-dose cholecalciferol failed to increase serum 25-hydroxyvitamin D level to 30 ng/mL (to convert to nanomoles per liter, multiply by 2.496) in most of patients. Furthermore, low-dose cholecalciferol also failed to improve calcium absorption in postmenopausal women with vitamin D insufficiency, which provided evidence against treatment with low-dose cholecalciferol. Alternatively, the failure to show improvement in calcium absorption could be owing to issues in the measurement of TFCA. Last, we would like to point out contradictive conclusions between the abstract and body of the paper. In the abstract, the authors concluded that “High-dose cholecalciferol therapy increased calcium absorption,”1(p1612) while in the conclusion section the author stated that “One year of high-dose cholecalciferol…had a negligible effect on calcium absorption.”1(p1619) Our main concern is the negative publicity of vitamin D supplement that could very well be type 1 error and dissuade physicians to prescribe vitamin D supplements and patients to take vitamin D supplements. The only conclusion that should be drawn from this study is that this study cannot exclude the beneficial effect of vitamin D replacement on bone outcomes. Back to top Article Information Corresponding Author: Ken C. Chiu, MD, Department of Clinical Diabetes, Endocrinology, and Metabolism, City of Hope National Medical Center, 1500 E Duarte Rd, Duarte, CA 91010-3000 (kchiu@coh.org). Conflict of Interest Disclosures: None reported. References 1. Hansen KE, Johnson RE, Chambers KR, et al. Treatment of vitamin D insufficiency in postmenopausal women: a randomized clinical trial . JAMA Intern Med. 2015;175(10):1612-1621.PubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA Internal Medicine American Medical Association

Proposed Guidelines for Future Vitamin D Studies

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References (1)

Publisher
American Medical Association
Copyright
Copyright © 2016 American Medical Association. All Rights Reserved.
ISSN
2168-6106
eISSN
2168-6114
DOI
10.1001/jamainternmed.2015.7974
Publisher site
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Abstract

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. This study further demonstrated that low-dose cholecalciferol failed to increase serum 25-hydroxyvitamin D level to 30 ng/mL (to convert to nanomoles per liter, multiply by 2.496) in most of patients. Furthermore, low-dose cholecalciferol also failed to improve calcium absorption in postmenopausal women with vitamin D insufficiency, which provided evidence against treatment with low-dose cholecalciferol. Alternatively, the failure to show improvement in calcium absorption could be owing to issues in the measurement of TFCA. Last, we would like to point out contradictive conclusions between the abstract and body of the paper. In the abstract, the authors concluded that “High-dose cholecalciferol therapy increased calcium absorption,”1(p1612) while in the conclusion section the author stated that “One year of high-dose cholecalciferol…had a negligible effect on calcium absorption.”1(p1619) Our main concern is the negative publicity of vitamin D supplement that could very well be type 1 error and dissuade physicians to prescribe vitamin D supplements and patients to take vitamin D supplements. The only conclusion that should be drawn from this study is that this study cannot exclude the beneficial effect of vitamin D replacement on bone outcomes. Back to top Article Information Corresponding Author: Ken C. Chiu, MD, Department of Clinical Diabetes, Endocrinology, and Metabolism, City of Hope National Medical Center, 1500 E Duarte Rd, Duarte, CA 91010-3000 (kchiu@coh.org). Conflict of Interest Disclosures: None reported. References 1. Hansen KE, Johnson RE, Chambers KR, et al. Treatment of vitamin D insufficiency in postmenopausal women: a randomized clinical trial . JAMA Intern Med. 2015;175(10):1612-1621.PubMedGoogle ScholarCrossref

Journal

JAMA Internal Medicine – American Medical Association

Published: Feb 1, 2016

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