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Use of Placebo in Supplementation Studies—Vitamin D Research Illustrates an Ethical Quandary

The George Washington School of Medicine and Health Sciences, Washington, DC 20052, USA
The University of Chicago Pritzker School of Medicine, Chicago, IL 60637, USA
The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
The Johns Hopkins Berman Institute of Bioethics, Baltimore, MD 21205, USA
The Johns Hopkins Weight Management Center, Baltimore, MD 21205, USA
The Global Obesity Prevention Center at Johns Hopkins, Baltimore, MD 21205, USA
Author to whom correspondence should be addressed.
Nutrients 2018, 10(3), 347;
Received: 3 February 2018 / Revised: 5 March 2018 / Accepted: 9 March 2018 / Published: 13 March 2018
PDF [220 KB, uploaded 13 March 2018]


History has shown that without explicit and enforced guidelines, even well-intentioned researchers can fail to adequately examine the ethical pros and cons of study design choices. One area in which consensus does not yet exist is the use of placebo groups in vitamin supplementation studies. As a prime example, we focus on vitamin D research. We aim to provide an overview of the ethical issues in placebo-controlled studies and guide future discussion about the ethical use of placebo groups. Research in the field of vitamin D shows variation in how placebo groups are used. We outline four types of control groups in use: active-control, placebo-control with restrictions on supplementation, placebo-control without supplementation restrictions, and placebo-control with rescue repletion therapy. The first two types highlight discrete ethical issues: active-control trials limit the ability to detect a difference; placebo-control trials that restrict supplementation potentially place subjects at risk of undue harm. The final two, placebo-control without supplementation restrictions or with rescue repletion therapy, offer potential solutions to these ethical challenges. Building on this, guidelines should be established and enforced on the use of placebo in supplementation studies. Furthermore, the field of vitamin D research has the potential to set an example worthy of emulation. View Full-Text
Keywords: nutrition therapy; dietary supplements; research ethics; research design; vitamin D nutrition therapy; dietary supplements; research ethics; research design; vitamin D
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Frame, L.A.; Fischer, J.P.; Geller, G.; Cheskin, L.J. Use of Placebo in Supplementation Studies—Vitamin D Research Illustrates an Ethical Quandary. Nutrients 2018, 10, 347.

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