title: Duration of physical activity and serum 25-hydroxyvitamin D status of postmenopausal women.
abstract: OBJECTIVE
  To investigate whether the association between physical activity and serum 25-hydroxyvitamin D (25(OH)D) concentrations is independent of sun exposure, body size, and other potential explanatory variables.
  
  
  METHODS
  By using data from a sample of 1343 postmenopausal women from the Women's Health Initiative, we used linear regression to examine the associations of duration (minutes/week) of recreational activity and of yard work with 25(OH)D concentrations (nmol/L).
  
  
  RESULTS
  In age-adjusted analyses, positive associations were observed between 25(OH)D concentrations and both duration of recreational physical activity (β = 0.71, SE [0.09], p <.001) and yard work (β = 0.36, SE [0.10], p = .004). After further adjustment for vitamin D intake, self-reported sunlight exposure, waist circumference, and season of blood draw, 25(OH)D was significantly associated with recreational activity (β = 0.21, SE [0.09], p = .014) but not with yard work (β = 0.18, SE [0.09], p = .061). Interactions were observed between season and both recreational activity (P(interaction) = .082) and yard work (P(interaction) = .038) such that these activity-25(OH)D associations were greater during summer/fall compared with winter/spring. Self-reported sunlight exposure and measures of body size did not modify the associations.
  
  
  CONCLUSIONS
  The observed age-adjusted activity-25(OH)D associations were attenuated after adjusting for explanatory variables and were modified by season of blood draw. Adopting a lifestyle that incorporates outdoor physical activity during summer/fall, consuming recommended amounts of vitamin D, and maintaining a healthy weight may improve or maintain vitamin D status in postmenopausal women.
authors.affiliation: Department of Social and Preventive Medicine, School of Public Health and Health Professions, University at Buffalo, NY 14214-8001, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Kluczynski
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lamonte
authors.forename: Julie A
authors.initials: JA
authors.lastname: Mares
authors.forename: Jean
authors.initials: J
authors.lastname: Wactawski-Wende
authors.forename: Ashley Wilder
authors.initials: AW
authors.lastname: Smith
authors.forename: Corinne D
authors.initials: CD
authors.lastname: Engelman
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Andrews
authors.forename: Linda G
authors.initials: LG
authors.lastname: Snetselaar
authors.forename: Gloria E
authors.initials: GE
authors.lastname: Sarto
authors.forename: Amy E
authors.initials: AE
authors.lastname: Millen
mesh_terms: D000368:Aged; D000886:Anthropometry; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D017698:Postmenopause / Q000502:physiology*; D011446:Prospective Studies; D013997:Time Factors; D014466:Ultraviolet Rays; D014481:United States; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D