title: Potential determinants of vitamin D in Finnish adults: a cross-sectional study from the Northern Finland birth cohort 1966.
abstract: Evidence from randomised controlled trials suggests that vitamin D may reduce multimorbidity, but very few studies have investigated specific determinants of vitamin D2 and D3 (two isoforms of 25-hydroxyvitamin D). The aim of the study was to investigate the determinants of vitamin D2 and D3 and to identify the risk factors associated with hypovitaminosis D.
  
  
  
  Cross-sectional study.
  
  
  
  Northern Finland Birth Cohort 1966.
  
  
  
  2374 male and 2384 female participants with data on serum 25(OH)D2and 25(OH)D3concentrations measured at 31 years of age (1997), together with comprehensive measures of daylight, anthropometric, social, lifestyle and contraceptive cofactors.
  
  
  
  We assessed a wide range of potential determinants prior to a nationwide fortification programme introduced in Finland. The determinants of 25(OH)D2, 25(OH)D3and 25(OH)D concentrations were analysed by linear regression and risk factors for being in lower tertile of 25(OH)D concentration by ordinal logistic regression.
  
  
  
  At the time of sampling, 72% of the participants were vitamin D sufficient (≥50 nmol/L). Low sunlight exposure period (vs high) was associated positively with 25(OH)D2and negatively with 25(OH)D3concentrations. Use of oral contraceptives (vs non-users) was associated with an increase of 0.17 nmol/L (95% CI 0.08 to 0.27) and 0.48 nmol/L (95% CI 0.41 to 0.56) in 25(OH)D2and 25(OH)D3concentrations. Sex, season, latitude, alcohol consumption and physical activity were the factors most strongly associated with 25(OH)D concentration. Risk factors for low vitamin D status were low sunlight exposure defined by time of sampling, residing in northern latitudes, obesity, higher waist circumference, low physical activity and unhealthy diet.
  
  
  
  We demonstrate some differential associations of environmental and lifestyle factors with 25(OH)D2and 25(OH)D3raising important questions related to personalised healthcare. Future strategies could implement lifestyle modification and supplementation to improve vitamin D2 and D3 status, accounting for seasonal, lifestyle, metabolic and endocrine status.
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland.|Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.
authors.forename: Saranya
authors.initials: S
authors.lastname: Palaniswamy
authors.affiliation: Centre for Population Health Research, School of Health Sciences and Sansom Institute, University of South Australia, South Australian Health and Medical Research Institute, Adelaide, Australia.|Population, Policy and Practice, Institute of Child Health, University College London, London, UK.
authors.forename: Elina
authors.initials: E
authors.lastname: Hyppönen
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Dylan M
authors.initials: DM
authors.lastname: Williams
authors.affiliation: Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.|MRC and Unit of Primary Care, Oulu University Hospital, Oulu, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Jokelainen
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland.|Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.
authors.forename: Estelle
authors.initials: E
authors.lastname: Lowry
authors.affiliation: Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.|MRC and Unit of Primary Care, Oulu University Hospital, Oulu, Finland.
authors.forename: Sirkka
authors.initials: S
authors.lastname: Keinänen-Kiukaanniemi
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland.|Department of Physiology, Institute of Biomedicine, University of Oulu, Oulu, Finland.|Department of Gastroenterology and Metabolism, Poznan University of Medical Sciences, Poznan, Poland.|CEU Cardenal Herrera University, Valencia, Spain.
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Herzig
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland.|Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.|MRC and Unit of Primary Care, Oulu University Hospital, Oulu, Finland.|Department of Epidemiology and Biostatistics, School of Public health, Imperial College London, London, UK.|MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
authors.forename: Marjo-Riitta
authors.initials: MR
authors.lastname: Järvelin
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland.|Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland.|Department of Genomics of Complex Diseases, School of Public Health, Imperial College London, London, UK.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Sebert
mesh_terms: D000328:Adult; D000886:Anthropometry; D003267:Contraception; D003430:Cross-Sectional Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008019:Life Style; D008297:Male; D012307:Risk Factors; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000453:epidemiology*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-hydroxyvitamin D; Northern Finland; Vitamin D