title: Relative effectiveness of oral 25-hydroxyvitamin D3 and vitamin D3 in raising wintertime serum 25-hydroxyvitamin D in older adults.
abstract: BACKGROUND
  The relative potency of 25-hydroxyvitamin D3 to vitamin D3 needs to be better defined so that food-composition tables can better reflect the true vitamin D nutritive value of certain foods.
  
  
  OBJECTIVE
  We performed a randomized, controlled intervention study in apparently healthy, free-living adults to investigate whether the intake of 25-hydroxyvitamin D3 is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D3.
  
  
  METHODS
  A randomized, placebo-controlled, double-blind intervention study was conducted in adults aged ≥50 y (n = 56) who consumed a placebo, 20 μg vitamin D3, or 7 or 20 μg 25-hydroxyvitamin D3 daily throughout 10 wk of winter. Serum 25(OH)D was measured by using an enzyme-linked immunoassay, and serum albumin-corrected calcium (S-Ca) was assessed colorimetrically at the baseline, midpoint, and endpoint of the study.
  
  
  RESULTS
  The mean (±SD) increases (per microgram of vitamin D compound) in serum 25(OH)D concentrations over baseline after 10 wk of supplementation were 0.96 ± 0.62, 4.02 ± 1.27, and 4.77 ± 1.04 nmol · L(-1) · μg intake(-1) for the 20-μg vitamin D3/d and 7- and 20-μg 25-hydroxyvitamin D3/d groups, respectively. A comparison of the 7- and 20-μg 25-hydroxyvitamin D3/d groups with the 20-μg vitamin D3/d group yielded conversion factors of 4.2 and 5, respectively. There was no effect of treatment on S-Ca concentrations and no incidence of hypercalcemia (S-Ca >2.6 nmol/L).
  
  
  CONCLUSIONS
  Each microgram of orally consumed 25-hydroxyvitamin D3 was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D3. This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at clinicaltrials.gov as NCT01398202.
authors.affiliation: School of Food and Nutritional Sciences, Department of Medicine, University College Cork, Cork, Ireland. k.cashman@ucc.ie
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Cashman
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Seamans
authors.forename: Alice J
authors.initials: AJ
authors.lastname: Lucey
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Stöcklin
authors.forename: Peter
authors.initials: P
authors.lastname: Weber
authors.forename: Mairead
authors.initials: M
authors.lastname: Kiely
authors.forename: Tom R
authors.initials: TR
authors.lastname: Hill
mesh_terms: D000284:Administration, Oral; D002112:Calcifediol / Q000097:blood / Q000494:pharmacology*; D002118:Calcium / Q000097:blood; D002762:Cholecalciferol / Q000097:blood / Q000494:pharmacology*; D004032:Diet; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000517:prevention & control*; D014815:Vitamins / Q000097:blood / Q000494:pharmacology
chemical_list: D014815:Vitamins; D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D; D002112:Calcifediol; D002118:Calcium