title: Plasma vitamin D and 25OHD responses of young and old men to supplementation with vitamin D3.
abstract: OBJECTIVE
  This study was conducted to determine whether there are age differences in the plasma parent vitamin D and 25-hydroxyvitamin D (25OHD) responses to eight weeks of supplementation with 20 microg/day of vitamin D3.
  
  
  METHODS
  Twenty-five healthy young men (age 18-35) and 25 healthy older men (62-79) were randomly assigned to supplementation with 20 microg/day of vitamin D3 or to no intervention and followed for eight weeks. Plasma vitamin D3 was measured by high performance liquid chromatography and 25OHD was measured by competitive protein binding.
  
  
  RESULTS
  Both young and old men in the supplemented group had pronounced, rapid and similar increases in plasma vitamin D3, whereas vitamin D3 concentrations were stable in the control group. By the end of the eight-week adaptation period, plasma vitamin D3 of young and old men had increased by 4.3 and 6.2 nmol/L respectively. In the supplemented group, mean 25OHD concentrations of both the young and old men increased during the study, and the magnitude of the change after eight weeks was nearly identical in the two age groups (22.5 and 22.1 nmol/L in the young and the old men, respectively). In the control group there was a modest decrease in 25OHD of both the young and old men.
  
  
  CONCLUSIONS
  There appears to be no age-related impairment among men in the absorption or metabolism of 20 microg/day of vitamin D3 taken orally for at least eight weeks.
authors.affiliation: Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University Boston, Massachusetts 02111, USA. sharris@hnrc.tufts.edu
authors.forename: Susan S
authors.initials: SS
authors.lastname: Harris
authors.forename: Bess
authors.initials: B
authors.lastname: Dawson-Hughes
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001667:Binding, Competitive; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D