title: 25-Hydroxyvitamin D response to graded vitamin D₃ supplementation among obese adults.
abstract: BACKGROUND
  Guidelines have suggested that obese adults need 2 to 3 times more vitamin D than lean adults to treat vitamin D deficiency, but few studies have evaluated the vitamin D dose response in obese subjects.
  
  
  OBJECTIVE
  The purpose of this study was to characterize the pharmacokinetics of 25-hydroxyvitamin D [25(OH)D] response to 3 different doses of vitamin D₃ (cholecalciferol) in a group of obese subjects and to quantify the 25(OH)D dose-response relationship. DESIGN, SETTING, INTERVENTION, PATIENTS: This was a randomized, single-blind study of 3 doses of oral vitamin D₃ (1000, 5000, or 10,000 IU) given daily to 67 obese subjects for 21 weeks during the winter months.
  
  
  METHODS
  Serum 25(OH)D levels were measured at baseline and after vitamin D replacement, and 25(OH)D pharmacokinetic parameters were determined, fitting the 25(OH)D concentrations to an exponential model.
  
  
  RESULTS
  Mean measured increments in 25(OH)D at week 21 were 12.4 ± 9.7 ng/mL in the 1000 IU/d group, 27.8 ± 10.2 ng/mL in the 5000 IU/d group, and 48.1 ± 19.6 ng/mL in the 10,000 IU/d group. Steady-state increments computed from the model were 20.6 ± 17.1, 35.2 ± 14.6, and 51.3 ± 22.0 ng/mL, respectively. There were no hypercalcuria or hypercalcemia events during the study.
  
  
  CONCLUSIONS
  Our data show that in obese people, the 25(OH)D response to vitamin D₃ is directly related to dose and body size with ∼2.5 IU/kg required for every unit increment in 25(OH)D (nanograms per milliliter).
authors.affiliation: MD, 984120 Nebraska Medical Center, Omaha, NE 68198-4120. andjela.drincic@unmc.edu.
authors.forename: Andjela
authors.initials: A
authors.lastname: Drincic
authors.forename: Eileen
authors.initials: E
authors.lastname: Fuller
authors.forename: Robert P
authors.initials: RP
authors.lastname: Heaney
authors.forename: Laura A G
authors.initials: LA
authors.lastname: Armas
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002112:Calcifediol / Q000097:blood* / Q000378:metabolism; D002118:Calcium / Q000097:blood / Q000652:urine; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism / Q000627:therapeutic use; D015331:Cohort Studies; D019587:Dietary Supplements / Q000009:adverse effects; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009329:Nebraska; D009765:Obesity / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology / Q000652:urine; D010281:Parathyroid Hormone / Q000097:blood; D064167:Recommended Dietary Allowances; D012621:Seasons; D016037:Single-Blind Method; D014808:Vitamin D Deficiency / Q000209:etiology / Q000517:prevention & control*
chemical_list: C470125:PTH protein, human; D010281:Parathyroid Hormone; D002762:Cholecalciferol; D002112:Calcifediol; D002118:Calcium