title: Effect of sunlight exposure on serum 25-hydroxyvitamin d concentration in women with vitamin d deficiency: using ambulatory lux meter and sunlight exposure questionnaire.
abstract: BACKGROUND
  Vitamin D is an important factor in human health. Yet, vitamin D deficiency is very common. We aimed to confirm serum 25-hydroxyvitamin D (25OHD) concentration change after sunlight exposure and to elucidate the relationship between the amount of sunlight exposure and serum 25OHD level change by ambulatory lux meter and sunlight exposure questionnaire.
  
  
  METHODS
  Twenty healthy young women were enrolled. They were educated to obtain 20 minutes of sunlight exposure during weekdays from October to November, 2010, during which they were to wear an ambulatory lux meter on an arm. All subjects completed a one-week recall sunlight exposure questionnaire at the end of the study. Before and after sunlight exposure, serum 25OHD level was measured.
  
  
  RESULTS
  Mean pre-exposure serum 25OHD concentration was 11.01 ng/mL. The mean change of pre- and post-exposure 25OHD level was -0.62 ng/mL, but it was not statistically significant. The mean personal sunlight exposure recorded by ambulatory lux meter, 292.6 lux/s, showed no significant relationship with average change of 25OHD and average weekly sunlight exposure score, 11.9, calculated by the sunlight exposure questionnaire. However, the mean change of serum 25OHD level and weekly sunlight exposure score showed significant negative correlation (r = -0.469, P = 0.037).
  
  
  CONCLUSIONS
  Change of serum 25OHD concentration after four weeks of sunlight exposure was not statistically significant in women with vitamin D deficiency. However, serum 25OHD concentration change was significantly negatively correlated with the sunlight exposure score by the questionnaire.
authors.affiliation: Department of Family Practice and Community Health, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Sang-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Soo-Jung
authors.initials: SJ
authors.lastname: Park
authors.forename: Kwang-Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Duck-Joo
authors.initials: DJ
authors.lastname: Lee
authors.forename: Woo-Jae
authors.initials: WJ
authors.lastname: Kim
authors.forename: Rae-Woong
authors.initials: RW
authors.lastname: Park
authors.forename: Nam-Seok
authors.initials: NS
authors.lastname: Joo