Vitamin D Status and Selected Metabolic Parameters in Salt Mine Workers: A Cross-Sectional Study

Background: Vitamin D deficiency has been implicated in disturbances of glucose and lipid metabolism, particularly in occupational groups with limited sunlight exposure. This study aimed to examine the association between serum 25-hydroxyvitamin D [25(OH)D] concentrations and markers of carbohydrate and lipid metabolism in salt mine workers. Methods: This cross-sectional study involved 62 male salt miners (aged 25-63 years), stratified by work depth (surface, ≤750 m, and >750 m). Anthropometric characteristics, body composition, cardiorespiratory fitness (VO_2max), and biochemical parameters were assessed. Blood analyses included fasting glucose, insulin, lipid profile, TSH, and 25(OH)D. Insulin resistance was evaluated via the HOMA-IR index. Results: The cohort exhibited a high prevalence of overweight and obesity (mean BMI > 28 kg/m²). Significant differences in VO_2max were observed between groups (p < 0.05). Elevated fasting glucose (>100 mg/dL) was observed in 47% of participants, and 22% presented HOMA-IR values > 2.5. In the regression model, vitamin D supplementation was the strongest predictor of 25(OH)D levels, explaining 25.5% of its variance. The addition of HDL cholesterol increased the explained variance to 35.6%, whereas HOMA-IR contributed an additional 3.9% (p = 0.094). Conclusions: In salt miners, insufficient vitamin D status coexists with excess adiposity and impaired glucose homeostasis. Serum 25(OH)D was more strongly associated with supplementation and HDL-C than with HOMA-IR. These findings suggest that monitoring vitamin D status is relevant in the occupational health evaluation of this group.