Abstract
Background and objectives: Large improvements in vitamin D status (serum 25-hydroxyvitamin D; S-25(OH)D) have been recorded among the general Finnish population, mainly due to vitamin D fortification policies and supplement use. Vitamin D intake has increased since the beginning of the fortification scheme in 2003 and subsequently by its increment in 2010. Also, vitamin D supplement use has increased over the years. However, whether sufficient vitamin D status lowers the risk of diabetes is unclear. Hence, we investigated the association between the improved vitamin D status in the Finnish adult population and long-term incidence of type 2 diabetes (T2D). Methods: This study evaluated data of Finnish adults aged ≥30 years (n = 3014) in a longitudinal setting (Health 2000/2011 cohort) who did not have T2D at baseline. The S-25(OH)D concentrations from both time points (years 2000 and 2011) were standardized according to the Vitamin D Standardization Program. The survey datasets were linked with incident T2D datasets from the national register for the time period 2000–2019. Associations between vitamin D status, change in S-25(OH)D concentrations and incidence of T2D over the 8-year follow-up period were assessed using logistic and Cox regression models (adjusted for age, sex and blood sampling season, etc.). Results: Over the 8-year follow-up period, 214 T2D incident cases were observed in subjects who participated in both Health 2000 and Health 2011. We observed a borderline significantly lower mean baseline S-25(OH)D concentration among T2D cases (45.4 [SD = 12.3] nmol/L) compared with participants not having T2D (48.1 [SD = 134.6] nmol/L) (p = 0.01). Having a sufficient vitamin D status (S-25(OH)D ≥50 nmol/L) at baseline was associated with lower odds of T2D (adjusted OR 0.94 [95% CI 0.89–0.98]). In participants whose S-25(OH)D concentrations increased over the years, the T2D incidence was lowered (adjusted HR 0.01 [95% CI 0.00–0.01] and 0.82 [95% CI 0.76–0.89] for ∆ ≥50 nmol/L). Discussion: Our preliminary findings indicate a protective effect of increased 25(OH)D (up to 50 nmol/L) against T2D among Finnish adults with an initially low vitamin D status. This study shows that well-designed longitudinal cohorts using standardized methods carry valuable potential to evaluate national nutrition status and to investigate the relationship between nutrition status and chronic diseases.
Author Contributions
Conceptualization, F.A.A., S.T.I., M.E. and C.L.-A.; methodology, T.J., T.H. and K.D.C.; validation, T.J., T.H. and C.L.-A.; formal analysis, F.A.A.; data curation, T.J.; writing—original draft preparation, F.A.A.; writing—review and editing, F.A.A., S.T.I., T.H., M.E. and C.L.-A.; supervision, T.J., S.T.I., M.E. and C.L.-A.; project administration, C.L.-A.; funding acquisition, F.A.A. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Otto A. Malm Foundation and Ella and Georg Ehrnrooth Foundation.
Institutional Review Board Statement
Both surveys (Health 2000/2011) were conducted in accordance with the Declaration of Helsinki. The protocol for Health 2000 was approved by the Ethical Committee for Research in Epidemiology and Public Health, while Health 2011 was approved by the Coordinating Ethics Committee at the Hospital District of Helsinki and Uusimaa in Finland. Ethics approval for the usage and linkage of survey datasets to national registers was obtained from the Finnish Institute for Health and Welfare.
Informed Consent Statement
Written informed consent was obtained from all subjects involved in the study.
Data Availability Statement
Restrictions apply to the availability of these data. Data was obtained from the Finnish Institute for Health and Welfare with permission (https://thl.fi/en/web/thlfi-en/research-and-development/research-and-projects/health-2000-2011).
Conflicts of Interest
The authors declare no conflict of interest.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).