In men, variables showing a significant difference in the distribution and the mean value in serum 25(OH)D level were age (P < 0.001), current smoker (P = 0.001), WM (P = 0.009), BMI (P < 0.001), TGs (P < 0.001), HDL-C (P = 0.010), Hb (P = 0.002), Hct (P = 0.023), MCV (P = 0.010), metabolic syndrome (P = 0.013), and ferritin (P < 0.001). The gene discussed is GSTM1; the disease is metabolic syndrome.