Predictors of vitamin D biochemical status in a large sample of middle-aged male smokers in Finland

Background/Objectives: As vitamin D deficiency is considered to be more common in regions with little solar ultraviolet (UV) light in winter, the aim of this study was to analyze predictors of vitamin D status by season within a large sample of male smokers from Finland, a country where there is negligible solar UV light in winter. Subjects/Methods: Vitamin D ( measured by 25-hydroxyvitamin D (25(OH) D) nmol/l) and other serum constituents were assayed. Measured anthropometry, and self-reported dietary intake and physical activity (PA) were obtained and analyzed using stepwise multiple linear and logistic regression in 2271 middle-aged Finnish male smokers. Results: In all, 27% of the population in winter and 17% in summer had serum 25( OH) D levels of <25 nmol/l, respectively. In summer, in multiple logistic regression analyses with adjustment for confounding and other predictors, high vitamin D intake ( odds ratios ( OR) 3.6; 95% confidence interval (CI) 1.5-8.5), some leisure time PA ( OR 2.0; 95% CI 1.3-3.1) and having a body mass index (BMI) of >= 21 kg/m(2) compared with <21 kg/m(2) ( OR 2.6; 95% CI 1.3-5.0), were associated with 25(OH) D >= 25 nmol/l. In winter, additional modifiable factors were occupational PA ( OR 1.6; 95% CI 1.1-2.5) and high fish ( OR 3.1; 95% CI 1.7-6.2) or poultry consumption ( OR 1.7; 95% CI 1.2-2.5). Predictors from linear regression analyses of continuous levels of 25( OH) D were similar to the logistic regression analyses of 25( OH) D >= 25 nmol/l. Conclusion: In this Finnish sample more vitamin D intake, PA and having a BMI of >= 21 may have important modifiable roles in maintaining an adequate vitamin D status. European Journal of Clinical Nutrition ( 2010) 64, 280-288; doi:10.1038/ejcn.2009.137; published online 6 January 2010