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Potential determinants of vitamin D in Finnish adults: a cross-sectional study from the Northern Finland birth cohort 1966
  1. Saranya Palaniswamy1,2,
  2. Elina Hyppönen3,4,
  3. Dylan M Williams5,
  4. Jari Jokelainen2,6,
  5. Estelle Lowry1,2,
  6. Sirkka Keinänen-Kiukaanniemi2,6,
  7. Karl-Heinz Herzig1,7,8,9,
  8. Marjo-Riitta Järvelin1,2,6,10,11,
  9. Sylvain Sebert1,2,12
  1. 1Biocenter Oulu, University of Oulu, Oulu, Finland
  2. 2Faculty of Medicine, Center for Life Course Health Research, University of Oulu, Oulu, Finland
  3. 3Centre for Population Health Research, School of Health Sciences and Sansom Institute, University of South Australia, South Australian Health and Medical Research Institute, Adelaide, Australia
  4. 4Population, Policy and Practice, Institute of Child Health, University College London, London, UK
  5. 5Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
  6. 6MRC and Unit of Primary Care, Oulu University Hospital, Oulu, Finland
  7. 7Department of Physiology, Institute of Biomedicine, University of Oulu, Oulu, Finland
  8. 8Department of Gastroenterology and Metabolism, Poznan University of Medical Sciences, Poznan, Poland
  9. 9CEU Cardenal Herrera University, Valencia, Spain
  10. 10Department of Epidemiology and Biostatistics, School of Public health, Imperial College London, London, UK
  11. 11MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK
  12. 12Department of Genomics of Complex Diseases, School of Public Health, Imperial College London, London, UK
  1. Correspondence to Dr Saranya Palaniswamy; saranya.palaniswamy{at}


Objective 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.

Design Cross-sectional study.

Setting Northern Finland Birth Cohort 1966.

Participants 2374 male and 2384 female participants with data on serum 25(OH)D2 and 25(OH)D3 concentrations measured at 31 years of age (1997), together with comprehensive measures of daylight, anthropometric, social, lifestyle and contraceptive cofactors.

Methods 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)D3 and 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.

Results 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)D2 and negatively with 25(OH)D3 concentrations. 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)D2 and 25(OH)D3 concentrations. 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.

Conclusions We demonstrate some differential associations of environmental and lifestyle factors with 25(OH)D2 and 25(OH)D3 raising 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.

  • Vitamin D
  • 25-hydroxyvitamin D
  • Northern Finland

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  • Contributors SP, MRJ and SS designed the analysis plan. SP conducted the analysis and wrote the manuscript with guidance from SS, JJ, DMW and MRJ. EH and MRJ were responsible for data collection of variables and blood sampling related to this analysis. EL reviewed/edited the manuscript. All authors contributed intellectually to the manuscript and approved the final version.

  • Funding This work was financially supported by the Academy of Finland (MRJ, grant number 24300796); Medical Research Council, UK (EH, grant number G0601653); Biocenter Oulu Doctoral Programme (SP); European Union's Horizon 2020 research and innovation programme (MRJ, SS, DMW, grant number 633595) for the DynaHEALTH action.

  • Disclaimer The funders had no role in the design, analysis or writing of this article.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval The study was approved by the ethical committee of University of Oulu and Northern Ostrobothnia Hospital District. The procedures follow the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Data are available on request to the NFBC1966 Data Sharing Committee. NFBC1966 data sharing policies and processes meet the requirement and expectations of Northern Ostrobothnia Hospital district policy on sharing of data from population and patient cohorts. Data requests should be submitted to; further details can be found at These policies and processes are in places to ensure the use of data from this prospective birth cohort study is within the bounds of consent given previously by study members, complies with Northern Ostrobothnia Hospital district guidance on ethics and research governance and meets rigorous University of Oulu data security standards.

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