title: Determinants of vitamin D status in older men living in a subtropical climate.
abstract: BACKGROUND
  Previously we reported seasonal variation in 25-hydroxyvitamin D (25OHD) levels in postmenopausal women living in a subtropical climate. Because studies have suggested that there are gender differences in 25OHD levels, we sought to determine (1) the levels and determinants of 25OHD in men drawn from the same community, (2) whether seasonal variation of 25OHD occurs in men at this latitude (37 degrees S), and (3) whether these findings were comparable to those we previously observed in postmenopausal women.
  
  
  METHODS
  Cross-sectional study of 378 healthy, middle-aged and older community-dwelling men in Auckland, New Zealand.
  
  
  RESULTS
  The mean 25OHD (SD) level was 85 (31) nmol/l. We found significant seasonal variation in 25OHD levels (peak in autumn 103 nmol/l, nadir in spring 59 nmol/l). Vitamin D insufficiency (25OHD <50 nmol/l) was uncommon (prevalence in summer 0-17%, in winter 0-20%). The major determinants of 25OHD were month of blood sampling, fat percentage, physical activity, and serum albumin. Men had higher levels of 25OHD throughout the year than women did, a finding that persisted after adjusting for potential confounding factors. In men and women the determinants of 25OHD were similar.
  
  
  CONCLUSIONS
  There is significant seasonal variation in 25OHD levels in men living in a subtropical climate. In contrast to postmenopausal women, men have low rates of suboptimal vitamin D status, even in winter. Routine vitamin D supplementation for this population of men is not warranted.
authors.affiliation: Osteoporosis Research Group, Department of Medicine, University of Auckland, Private Bag 92 019, Auckland, New Zealand. m.bolland@auckland.ac.nz
authors.forename: M J
authors.initials: MJ
authors.lastname: Bolland
authors.forename: A B
authors.initials: AB
authors.lastname: Grey
authors.forename: R W
authors.initials: RW
authors.lastname: Ames
authors.forename: B H
authors.initials: BH
authors.lastname: Mason
authors.forename: A M
authors.initials: AM
authors.lastname: Horne
authors.forename: G D
authors.initials: GD
authors.lastname: Gamble
authors.forename: I R
authors.initials: IR
authors.lastname: Reid
mesh_terms: D000273:Adipose Tissue / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001835:Body Weight / Q000502:physiology; D002980:Climate; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D004781:Environmental Exposure; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology / Q000208:ethnology; D015995:Prevalence; D012621:Seasons; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology / Q000208:ethnology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D