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

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Abstract
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 2 compared with 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.