title: Contributions of vitamin D intake and seasonal sunlight exposure to plasma 25-hydroxyvitamin D concentration in elderly women.
abstract: We investigated the contributions (1.00-8.03 micrograms/d, or 40-321 IU/d) of vitamin D intake and seasonal sunlight exposure to plasma 25(OH)D in 59 healthy women aged 70-97 y with a mean total vitamin D intake of 8.58 micrograms/d (343 IU/d). In the summer and winter, each subject had a fasting blood measurement and assessments of vitamin D intake and sunlight exposure. Vitamin D intake was significantly correlated with plasma 25(OH)D in the summer (r = 0.52, P < 0.01) and winter (r = 0.63, P < 0.01). The influence of sunlight exposure measured in the summer on the 25(OH)D concentration was dependent on the vitamin D intake. In subjects with lower vitamin D intakes (1.00-8.03 micrograms/d, or 40-321 IU/d), the wintertime 25(OH)D concentrations of those with low and high sunlight exposure were comparable. In subjects with higher vitamin D intakes (11.15-28.68 micrograms/d, or 446-1147 IU/d), however, the wintertime 25(OH)D concentrations of those with high sunlight exposure were lower than those with lower exposure [63.8 +/- 3.9 and 80.6 +/- 6.7 nmol/L, respectively, P = 0.066; P (intake by exposure interaction) < 0.05]. This suggests that the contribution of vitamin D intake to plasma 25(OH)D concentration may be influenced by sunlight exposure.
authors.affiliation: US Department of Agriculture, Human Nutrition Research Center on Aging at Tufts University, Boston 02111.
authors.forename: L M
authors.initials: LM
authors.lastname: Salamone
authors.forename: G E
authors.initials: GE
authors.lastname: Dallal
authors.forename: D
authors.initials: D
authors.lastname: Zantos
authors.forename: F
authors.initials: F
authors.lastname: Makrauer
authors.forename: B
authors.initials: B
authors.lastname: Dawson-Hughes
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage*
chemical_list: D006887:Hydroxycholecalciferols; D014807:Vitamin D