title: Determinants of vitamin D status in young adults: influence of lifestyle, sociodemographic and anthropometric factors.
abstract: Very few studies have investigated the determinants of circulating 25-hydroxyvitamin D (25[OH]D) in young adults (18-25 years old) using a set of variables that include lifestyle, sociodemographic, and anthropometric data. Our aim was to investigate the association between these variables and vitamin D status in a sample of untreated young adults.
  
  
  
  A total of 738 young adults were enrolled in a (June cross-sectional study 2012 to May 2014) and were recruited from educational institutions in the Copenhagen area. For multivariate logistic regression subjects was categorized based on 25[OH]D in serum into; vitamin D sufficiency (S-25[OH]D > 50 nmol/L), vitamin D insufficiency (25 nmol/L ≤ S-25[OH]D ≤ 50 nmol/L), vitamin D deficiency (S-25[OH]D < 25 nmol/L). Information on lifestyle factors and education was obtained by self-reported questionnaires.
  
  
  
  700 subjects with a valid measurement of S-25[OH]D and a completed questionnaire was analysed. 238 had vitamin D insufficiency, 135 had vitamin D deficiency of which 13 had severe vitamin D deficiency (S-25[OH]D < 12.5 nmol/L). The relative risk (RR) for vitamin D deficiency was highest for men 2.09 (1.52, 2.87); obese subjects 2.00 (1.27, 3.15); smokers 1.33 (1.02, 1.73); subjects who exercised 0-½ hours a week 1.88 (1.21, 2.94); and subjects who consumed fast food once a week 1.59 (1.05, 2.43). The relative risk was significantly lower for subjects who were studying for a Bachelor's degree (0.40 (0.23, 0.68). For vitamin D insufficiency, the highest RR was again for men 1.31 (1.06, 1.61); obese subjects 1.57 (1.17, 2.11); and subjects who exercised 0-½ hours a week 1.51 (1.11, 2.06).
  
  
  
  In this study of young adults, vitamin D deficiency was highly prevalent. Modifiable factors such as smoking, maintenance of normal BMI, and physical activity are all potential targets for interventional trials to determine the causal order; such knowledge would be useful in improving S-25[OH]D in young adults. The small group with severe vitamin D deficiency warrants increased attention.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Rigshospitalet, Nordre Ringvej 57, 2600, Copenhagen, Glostrup, Denmark. Rune.Tonnesen@dadlnet.dk.
authors.forename: Rune
authors.initials: R
authors.lastname: Tønnesen
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Rigshospitalet, Nordre Ringvej 57, 2600, Copenhagen, Glostrup, Denmark.
authors.forename: Peter Hambak
authors.initials: PH
authors.lastname: Hovind
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, University Hospital of Herlev, Copenhagen, Denmark.|Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lars Thorbjørn
authors.initials: LT
authors.lastname: Jensen
authors.affiliation: Department of Endocrinology PE and Research Centre of Ageing and Osteoporosis, Rigshospitalet, Copenhagen, Denmark.|Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Schwarz
mesh_terms: D000293:Adolescent; D000328:Adult; D000886:Anthropometry / Q000379:methods*; D003430:Cross-Sectional Studies; D003718:Denmark; D015444:Exercise; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D009765:Obesity / Q000150:complications; D015995:Prevalence; D012621:Seasons; D057566:Self Report; D012737:Sex Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications / Q000175:diagnosis*; D055815:Young Adult
chemical_list: D014807:Vitamin D
keywords: Alcohol; Education; Exercise; Fast food; Season; Sex; Smoking; Vitamin D; Young adults