title: Determinants of vitamin D deficiency among undergraduate medical students in Saudi Arabia.
abstract: OBJECTIVE
  The objectives of our study were to determine possible factors associated with low vitamin D levels in medical students.
  
  
  METHODS
  A cross-sectional study was performed among 255 first- to fifth-year male undergraduate medical students of one of the major universities in Saudi Arabia. Serum 25-hydroxyvitamin D (25(OH)D) levels were measured using electrochemiluminiscence. Multiple logistic regression analysis was performed.
  
  
  RESULTS
  Majority of Saudi medical students (75.2%) had 25(OH)D levels <30 nmol/l, defined as risk for deficiency by the Institute of Medicine. Multivariate analysis showed that the odds of having 25(OH)D serum levels of ⩾ 30 nmol/l were seven times higher both in students who took vitamin D (odds ratio (OR)=7.2, 95% confidence interval (CI)=1.8-29.9, P=0.006) or multivitamin supplements (OR=6.9, 95% CI=1.7-27.3, P=0.006) within 1 year. Students with a history of vitamin D testing >1 year before the study or moderate/vigorous physical activity (PA) had 4.4 (OR=4.4, 95% CI=1.7-11.4, P=0.003) and 2.7-fold (OR=2.7, 95% CI=1.3-5.3, P=0.006) higher odds of having 25(OH)D levels ⩾ 30 nmol/l, respectively. There was no significant association between 25(OH)D serum levels and average time spent outdoors per day (P=0.369) and type of clothing (long-sleeved vs short-sleeved; P=0.800).
  
  
  CONCLUSIONS
  Vitamin D deficiency was highly prevalent in Saudi medical students. Modifiable factors such as vitamin D intake and PA could be targeted for intervention. Further studies with standardized laboratory measurements of 25(OH)D are needed to explore the role of vitamin D testing in behavioral change, which may lead to increased serum 25(OH)D levels.
authors.affiliation: Prince Sattam Bin Abdul Aziz Research Chair of Epidemiology and Public Health, College of Medicine, King Saud University, Riyadh, Saudi Arabia.|Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: A A
authors.initials: AA
authors.lastname: BinSaeed
authors.affiliation: Prince Sattam Bin Abdul Aziz Research Chair of Epidemiology and Public Health, College of Medicine, King Saud University, Riyadh, Saudi Arabia.|Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: A A
authors.initials: AA
authors.lastname: Torchyan
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: B N
authors.initials: BN
authors.lastname: AlOmair
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: N S
authors.initials: NS
authors.lastname: AlQadhib
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: F M
authors.initials: FM
authors.lastname: AlSuwayeh
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: F M
authors.initials: FM
authors.lastname: Monshi
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: F I
authors.initials: FI
authors.lastname: AlRumaih
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: S A
authors.initials: SA
authors.lastname: AlQahtani
authors.affiliation: Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: N
authors.initials: N
authors.lastname: AlYousefi
authors.affiliation: Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: A
authors.initials: A
authors.lastname: Al-Drees
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D015444:Exercise; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D012529:Saudi Arabia / Q000453:epidemiology; D013337:Students, Medical; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D055815:Young Adult
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D