title: Vitamin D intake determines vitamin d status of postmenopausal women, particularly those with limited sun exposure.
abstract: Few detailed data are available on the wide range of determinants of vitamin D status among postmenopausal women, and it is also unclear whether there may be undiscovered determinants. The objective of this study was to comprehensively evaluate determinants of serum 25-hydroxyvitamin D [25(OH)D] concentrations in a large cohort of postmenopausal women. Data from a subset of the Women's Health Initiative Observational Study were analyzed (50-79 y; n = 3345). Information on diet, lifestyle behaviors, secondhand smoke, use of dietary supplements and medication, chronic diseases, and anthropometry was collected at baseline (1993-1998) and on sun exposure at year 4 follow-up. Linear regression was performed to estimate regression coefficients (β). Significant determinants were total vitamin D intake (food plus supplements per 100 IU/d, β = 2.08), years of supplemental vitamin D use (β = 0.15), total fat intake (grams per day, β = -0.03), smoking status (β = -2.64, current vs. never), regional solar irradiance (β = 6.26, 475-500 vs. 300-325 Langleys), daylight time spent outdoors in summer (β = 5.15, >2 h vs. <30 min/d), recreational physical activity (metabolic equivalent task per hour per week, β = 0.13), waist circumference (centimeters, β = -0.26), and race/ethnicity (β = -11.94, black vs. white). Total vitamin D intake (partial R(2) = 0.09) explained the most variance in serum 25(OH)D concentrations (total R(2) = 0.29). The association between total vitamin D intake and serum 25(OH)D concentrations was stronger among participants who spent less rather than more daylight time outdoors in summer (P-interaction = 0.026). History and medications for hypertension, hyperlipidemia, and type 2 diabetes and secondhand smoke exposure were not associated with serum 25(OH)D. In conclusion, dietary factors and sun exposure remain important determinants of vitamin D status in postmenopausal women. Vitamin D intake should be emphasized for those with limited sun exposure.
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA.
authors.forename: Ting-Yuan David
authors.initials: TY
authors.lastname: Cheng
authors.forename: Amy E
authors.initials: AE
authors.lastname: Millen
authors.forename: Jean
authors.initials: J
authors.lastname: Wactawski-Wende
authors.forename: Shirley A A
authors.initials: SA
authors.lastname: Beresford
authors.forename: Andrea Z
authors.initials: AZ
authors.lastname: LaCroix
authors.forename: Yingye
authors.initials: Y
authors.lastname: Zheng
authors.forename: Gary E
authors.initials: GE
authors.lastname: Goodman
authors.forename: Mark D
authors.initials: MD
authors.lastname: Thornquist
authors.forename: Marian L
authors.initials: ML
authors.lastname: Neuhouser
mesh_terms: D000368:Aged; D044383:Black People / Q000706:statistics & numerical data; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008019:Life Style; D016014:Linear Models; D008875:Middle Aged; D015999:Multivariate Analysis; D017698:Postmenopause / Q000378:metabolism*; D012907:Smoking / Q000453:epidemiology; D013472:Sunlight; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000188:drug therapy* / Q000453:epidemiology* / Q000378:metabolism; D014815:Vitamins / Q000008:administration & dosage* / Q000097:blood; D044465:White People / Q000706:statistics & numerical data
chemical_list: D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D