Estimation of the dietary requirement for vitamin D in free-living adults >=64 y of age.
BACKGROUND
Older adults may be more prone to developing vitamin D deficiency than younger adults. Dietary requirements for vitamin D in older adults are based on limited evidence.


OBJECTIVE
The objective was to establish the dietary intake of vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above various cutoffs between 25 and 80 nmol/L during wintertime, which accounted for the effect of summer sunshine exposure and diet.


METHODS
A randomized, placebo-controlled, double-blind, 22-wk intervention was conducted in men and women aged >/=64 y (n = 225) at supplemental levels of 0, 5, 10, and 15 microg vitamin D(3)/d from October 2007 to March 2008.


RESULTS
Clear dose-related increments (P < 0.0001) in serum 25(OH)D were observed with increasing supplemental vitamin D(3) intakes. The slope of the relation between total vitamin D intake and serum 25(OH)D was 1.97 nmol . L(-1) . microg intake(-1). The vitamin D intake that maintained serum 25(OH)D concentrations >25 nmol/L in 97.5% of the sample was 8.6 microg/d. Intakes were 7.9 and 11.4 microg/d in those who reported a minimum of 15 min daily summer sunshine exposure or less, respectively. The intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 17.2, 24.7, and 38.7 microg/d, respectively.


CONCLUSIONS
To ensure that the vitamin D requirement is met by the vast majority (>97.5%) of adults aged >/=64 y during winter, between 7.9 and 42.8 microg vitamin D/d is required, depending on summer sun exposure and the threshold of adequacy of 25(OH)D. This trial was registered at http://www.controlled-trials.com/ISRCTN20236112 as ISRCTN registration no. ISRCTN20236112.
Cashman
Kevin D
KD
Department of Food and Nutritional Sciences, University College, Cork, Ireland.
Wallace
Julie Mw
JM
Horigan
Geraldine
G
Hill
Tom R
TR
Barnes
Maria S
MS
Lucey
Alice J
AJ
Bonham
Maxine P
MP
Taylor
Nicola
N
Duffy
Emeir M
EM
Seamans
Kelly
K
Muldowney
Siobhan
S
Fitzgerald
Anthony P
AP
Flynn
Albert
A
Strain
J J
JJ
Kiely
Mairead
M
D000368:Aged; D002118:Calcium / Q000097:blood; D002762:Cholecalciferol / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009751:Nutritional Requirements; D010281:Parathyroid Hormone / Q000097:blood; D012621:Seasons; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000453:epidemiology
D010281:Parathyroid Hormone; D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D; D002118:Calcium