title: The vitamin d dose response in obesity.
abstract: OBJECTIVE
  The prevalence of vitamin D inadequacy is high in obese individuals. Determining the response of serum 25-hydroxyvitamin D (25[OH]D) to vitamin D3 supplementation in obese and nonobese individuals may lead to concurrent recommendations for optimal vitamin D intake in these populations. The objective of this study was to determine the dose response of vitamin D3 in subjects with a body mass index ≥35 kg/m2.
  
  
  METHODS
  Randomized, double-blind, placebo-controlled study. This study is an extension of our previous study of vitamin D dosing in healthy adults. After an assessment of baseline 25(OH)D levels, participants were randomized to a vitamin D supplementation arm (100 μg daily if baseline 25[OH]D was <50 nmol/L, or 50 μg daily if baseline 25[OH]D was ≥50 nmol/L) or placebo arm. Subjects with baseline 25(OH)D level ≥80 nmol/L were excluded from the study. Two months following randomization, a repeat 25(OH)D measurement was done.
  
  
  RESULTS
  Final analysis included 25 subjects (14 placebo, 11 active). At 2 months, serum 25(OH)D concentration increased to a mean of 75 nmol/L in the active group. Mean slope (i.e., vitamin D3 response), defined as 25(OH) D change/baseline dose, was 0.398 nmol/L/μg/day.
  
  
  CONCLUSIONS
  The dose response of vitamin D3 (slope) in obese subjects was significantly lower (P<.03) at 0.398 nmol/L/μg/day compared to the slope in the previous study of healthy subjects (0.66 nmol/L/μg/day). These results suggest that obese individuals may require 40% higher vitamin D intake than nonobese individuals to attain the same serum 25(OH)D concentration.
authors.affiliation: Bone Mineral Research Center, Winthrop University Hospital, Mineola, New York.
authors.forename: Ruban
authors.initials: R
authors.lastname: Dhaliwal
authors.affiliation: Bone Mineral Research Center, Winthrop University Hospital, Mineola, New York.
authors.forename: Mageda
authors.initials: M
authors.lastname: Mikhail
authors.affiliation: Bone Mineral Research Center, Winthrop University Hospital, Mineola, New York.
authors.forename: Martin
authors.initials: M
authors.lastname: Feuerman
authors.affiliation: Bone Mineral Research Center, Winthrop University Hospital, Mineola, New York.
authors.forename: John F
authors.initials: JF
authors.lastname: Aloia
mesh_terms: D002762:Cholecalciferol; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D009765:Obesity; D014807:Vitamin D; D014808:Vitamin D Deficiency
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol