Effects of Age and Renal Function on Vitamin D Status in Men

Background: In general, no study has examined the relationship between vitamin D status and key parameters of bone mineral homeostasis in healthy men in Iran. The effects of age and renal function on vitamin D status were determined in a cross-sectional study on a healthy population of Iranian men. Methods: From January through February 2001, 520 men, aged 20 – 74 years were selected through a cluster randomized sampling from Shiraz. Serum 25-hydroxyvitamin D, intact parathyroid hormone, calcium, phosphorus, alkaline phosphatase, creatinine, and albumin were measured. Pearson and partial correlation coefficients were used to determine the association between variables. Results: Five hundred twenty men with a mean±SD age of 45±15 years and a mean±SD 25-hydroxyvitamin D level of 35±17 nmol/L were enrolled into the study. Over 33.9% of men in Shiraz had a low level of 25-hydroxyvitamin D (≤25 nmol/L). Serum 25-hydroxyvitamin D did not decline with age in men. Serum parathyroid hormone increased significantly by age in men, but it did not correlate with the decline in creatinine clearance. Men had a decline in serum phosphorus (r=0.23, P<0.0001) and calcium (r=0.14, P=0.001) concentrations by age. Creatinine clearance declined with age. Conclusion: In healthy men, the serum level of 25-hydroxyvitamin D did not decline with age. Nonetheless, the prevalence of vitamin D deficiency is high which warrants consideration of dietary vitamin D supplement in men.