• Kimmie Ng, Jamil B Scott, Bettina F Drake, Andrew T Chan, Bruce W Hollis, Paulette D Chandler, Gary G Bennett, Edward L Giovannucci, Elizabeth Gonzalez-Suarez, Jeffrey A Meyerhardt, Karen M Emmons, and Charles S Fuchs.
• Department of Medical Oncology (KN, JAM, and CSF) and Center for Community-Based Research (JBS, EG-S, and KME), Dana-Farber Cancer Institute, Boston, MA; the Division of Public Health Sciences, Washington University School of Medicine, St Louis, MO (BFD); the Division of Gastroenterology, Massachusetts General Hospital, Boston, MA (ATC); the Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (ATC, ELG, and CSF); the Division of Pediatrics, Medical University of South Carolina, Charleston, SC (BWH); the Division of General Medicine, Brigham and Women's Hospital, Boston, MA (PDC); the Department of Psychology and Neuroscience, Duke University, Durham, NC (GGB); and the Departments of Nutrition (JBS and ELG) and Social and Behavioral Sciences (KME), Harvard School of Public Health, Boston, MA.
• Am. J. Clin. Nutr. 2014 Mar 1;99(3):587-98.

BackgroundAssociation studies have suggested that lower circulating 25-hydroxyvitamin D [25(OH)D] in African Americans may partially underlie higher rates of cardiovascular disease and cancer in this population. Nonetheless, the relation between vitamin D supplementation and 25(OH)D concentrations in African Americans remains undefined.ObjectiveOur primary objective was to determine the dose-response relation between vitamin D and plasma 25(OH)D.DesignA total of 328 African Americans in Boston, MA, were enrolled over 3 winters from 2007 to 2010 and randomly assigned to receive a placebo or 1000, 2000, or 4000 IU vitamin D₃/d for 3 mo. Subjects completed sociodemographic and dietary questionnaires, and plasma samples were drawn at baseline and 3 and 6 mo.ResultsMedian plasma 25(OH)D concentrations at baseline were 15.1, 16.2, 13.9, and 15.7 ng/mL for subjects randomly assigned to receive the placebo or 1000, 2000, or 4000 IU/d, respectively (P = 0.63). The median plasma 25(OH)D concentration at 3 mo differed significantly between supplementation arms at 13.7, 29.7, 34.8, and 45.9 ng/mL, respectively (P < 0.001). An estimated 1640 IU vitamin D₃/d was needed to raise the plasma 25(OH)D concentration to ≥ 20 ng/mL in ≥ 97.5% of participants, whereas a dose of 4000 IU/d was needed to achieve concentrations ≥ 33 ng/mL in ≥ 80% of subjects. No significant hypercalcemia was seen in a subset of participants.ConclusionsWithin African Americans, an estimated 1640 IU vitamin D₃/d was required to achieve concentrations of plasma 25(OH)D recommended by the Institute of Medicine, whereas 4000 IU/d was needed to reach concentrations predicted to reduce cancer and cardiovascular disease risk in prospective observational studies. These results may be helpful for informing future trials of disease prevention.

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