Correction: This article was corrected online April 4, 2016, to fix an error in the first sentence of the Methods section.
Published Online: January 7, 2013. doi:10.1001/jamainternmed.2013.3254
Author Contributions: Dr Cohen had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Cohen, Stevens, and Deuster. Acquisition of data: Attipoe, Travis, and Deuster. Analysis and interpretation of data: Cohen, Attipoe, Travis, and Deuster. Drafting of the manuscript: Cohen, Attipoe, and Stevens. Critical revision of the manuscript for important intellectual content: Cohen, Attipoe, Travis, and Deuster. Statistical analysis: Cohen and Attipoe. Obtained funding: Deuster. Administrative, technical, and material support: Cohen, Attipoe, Travis, and Deuster. Study supervision: Cohen and Deuster.
Conflict of Interest Disclosures: Mr Travis is an employee of NSF International. NSF International is a not-for-profit, nongovernmental standards developing organization that developed the US national standards for dietary supplements. Some of NSF Internationals clients are dietary supplement manufacturers.
Funding/Support: This study was supported by grant NA91FD from the Center Alliance for Dietary Supplement Research, Department of Defense.
Disclaimer: The views expressed are those of the authors and do not reflect the official position of the Uniformed Services University, Department of the Navy, or the US Department of Defense.
Additional Contributions: Amy Eichner, PhD (US Antidoping Agency), and Lori Bestervelt, PhD (NSF International), provided critical feedback on the conception and design of this study.