title: Dose response to vitamin D supplementation in African Americans: results of a 4-arm, randomized, placebo-controlled trial.
abstract: 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.
  
  
  METHODS
  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, 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.
  
  
  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.
authors.affiliation: 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.
authors.forename: Kimmie
authors.initials: K
authors.lastname: Ng
authors.forename: Jamil B
authors.initials: JB
authors.lastname: Scott
authors.forename: Bettina F
authors.initials: BF
authors.lastname: Drake
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Chan
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Hollis
authors.forename: Paulette D
authors.initials: PD
authors.lastname: Chandler
authors.forename: Gary G
authors.initials: GG
authors.lastname: Bennett
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Gonzalez-Suarez
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Meyerhardt
authors.forename: Karen M
authors.initials: KM
authors.lastname: Emmons
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
mesh_terms: D000328:Adult; D001741:Black or African American; D000368:Aged; D000369:Aged, 80 and over; D001900:Boston / Q000453:epidemiology; D002112:Calcifediol / Q000097:blood*; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology / Q000517:prevention & control*; D002762:Cholecalciferol / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D015331:Cohort Studies; D019587:Dietary Supplements / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D057194:Intention to Treat Analysis; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology / Q000517:prevention & control*; D010352:Patient Dropouts; D012307:Risk Factors; D012621:Seasons; D014808:Vitamin D Deficiency / Q000097:blood / Q000178:diet therapy* / Q000208:ethnology / Q000503:physiopathology
chemical_list: D002762:Cholecalciferol; D002112:Calcifediol