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Many healthy African Americans got above 33 ng with 4,000 IU of vitamin D – RCT March 2014

Dose response to vitamin D supplementation in African Americans: results of a 4-arm, randomized, placebo-controlled trial

Am J Clin Nutr March 2014 ajcn.067777
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
From the 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.
Sponsors did not participate in the design or conduct of the study; collection, analysis, or interpretation of data; preparation, review, or approval of the manuscript; or decision to submit the article for publication. Contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the National Cancer Institute or NIH, Department of Defense, American Society of Clinical Oncology, or The Conquer Cancer Foundation.
Supported by the National Cancer Institute at the NIH [P50CA127003; K07CA148894 (to KN); K22CA126992 (to GGB); 5K05CA124415 (to KME); and U01CA138962 (to PDC)], the Department of Defense Prostate Cancer Research Program [PC081669 (to BD)], an American Society of Clinical Oncology (ASCO) Career Development Award (to KN), and Pharmavite LLC.
Address reprint requests and correspondence to K Ng, Dana-Farber Cancer Institute, 450 Brookline Avenue, Dana 1220, Boston, MA 02215. E-mail: kimmie_ng at dfci.harvard.edu

Background: Association 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.

Objective: Our primary objective was to determine the dose-response relation between vitamin D and plasma 25(OH)D.

Design: A 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.

Results: Median 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 (placebo)
  • 29.7 (1000 IU)
  • 34.8 (2000 IU), and
  • 45.9 ng/mL (4,000 IU), 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.

Conclusions: Within 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.
This trial was registered at clinicaltrials.gov as http://clinicaltrials.gov/show/NCT00585637


See also VitaminDWiki

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It would appear from the chart from this other study that with 4,000 IU that 80% of A-A got >50 ng at 12 months

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