Smoking is a significant determinant of low serum vitamin D in young and middle-aged healthy males.

OBJECTIVE We aimed to determine the prevalence of 25(OH)D (D2 and D3 independently) inadequacy in healthy young/middle-aged men and to investigate its relationship with BMD, bone markers, demographic and lifestyle parameters such as age, BMI, smoking, alcohol consumption and dietary calcium intake. DESIGN We determined 25(OH)D levels using LC-MS/MS, a robust method for measurement of both 25(OH)D3 and 25(OH)D2, iPTH, osteocalcin, beta C terminal cross-linked telopeptides of type I collagen (b-CTXs), procollagen type 1 amino-terminal propeptide (PINP), BMD at L2-L4 and proximal femur, smoking habits, daily dietary calcium intake and alcohol consumption in 181 randomly selected healthy men aged 20-50y. RESULTS The prevalence of vitamin D deficiency (25(OH)D < 20 ng/ml) was 50.3%. Only 8.8% of the participants had vitamin D sufficiency (25(OH)D ≥ 30 ng/ml). We found a strong correlation between 25(OH)D and smoking in the totality of participants (p<0.001). 25(OH)D level was lower by approximately 4.3 ng/dl (p<0.001) in a smoker compared to a non-smoker among the totality of participants, while this value increased to 9.2 ng/ml in the 40-50y subgroup (p=0.003). A multinomial logistic regression model demonstrated that a young smoker (20-29y) had 58% increased likelihood of having vitamin D deficiency compared to a non-smoker of the same age group (p=0.041). CONCLUSIONS A high prevalence of vitamin D deficiency was identified in a young and middle-aged male population. Smoking is a significant determinant of serum 25(OH)D, while it increases significantly the likelihood of having vitamin D deficiency. In our hands, vitamin D levels are not a determinant of bone turnover and BMD in this population.