title: Plasma 25-hydroxyvitamin D responses of younger and older men to three weeks of supplementation with 1800 IU/day of vitamin D.
abstract: OBJECTIVE
  The objective of this study was to compare changes in plasma 25-hydroxyvitamin D (25(OH)D) levels of younger and older men after three weeks of oral vitamin D supplementation.
  
  
  METHODS
  Nine younger men (22 to 28 years) and nine older men (65 to 73 years) with self-reported vitamin D intakes below 200 IU/d were enrolled in February and randomized to 1800 IU/d of ergocalciferol (vitamin D2, n=11) or to a control group (n=7) and followed for three weeks. Blood was collected at baseline, and after one, two and three weeks for measurement of plasma concentrations of total 25(OH)D, 25(OH)D2 and 25(OH)D3.
  
  
  RESULTS
  In both the younger and older supplemented men, 25(OH)D2 and total 25(OH)D concentrations increased significantly during the study, whereas values of these metabolites did not change in younger or older control subjects. No group showed significant changes in 25-hydroxyvitamin D3. There was a significant interaction between age group and supplement group, suggesting that the effect of vitamin D2 supplementation on changes in 25(OH)D2 changes with age. The mean increase in 25(OH)D2 was greater in the younger supplemented men than in the older supplemented men (37+/-9 nmol/L vs. 19.5 nmol/L, p=0.027), and this accounted for their significantly greater increase in total 25(OH)D.
  
  
  CONCLUSIONS
  These data are consistent with an age-related decline in the absorption, transport or liver hydroxylation of orally-consumed vitamin D.
authors.affiliation: Jean Mayer United States Department of Agriculture, Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Harris
authors.forename: B
authors.initials: B
authors.lastname: Dawson-Hughes
authors.forename: G A
authors.initials: GA
authors.lastname: Perrone
mesh_terms: D000042:Absorption; D000328:Adult; D000368:Aged; D000375:Aging; D015992:Body Mass Index; D002112:Calcifediol / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D004872:Ergocalciferols / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D004872:Ergocalciferols; D002112:Calcifediol