Metabolism of Vitamin D is Not Affected by Sport Activity

Background: Higher levels of physical activity are related to higher 25-(OH)D levels. Total 25-(OH)D (25-(OH)D) are routinely used in clinical practice to assess vitamin D, however novel biomarkers are currently being investigated as free 25-(OH)D (25-(OH)D) or vitamin D metabolite ratios (VMRs). The primary aim of our study was to assess 25-(OH)D, vitamin D metabolites and VMRs in inactive men and athletes. A secondary aim was to check whether regular physical activity influence on vitamin D metabolome. A tertiary aim was to determine the relationship between 25-(OH)D, 25-(OH)D, vitamin D binding protein (VDBP), vitamin D metabolites and VMRs in this cohort.

Methods: A total of 69 participants (27 inactive men, 18 indoor and 24 outdoor athletes) participated in the study. Vitamin D metabolites (25-(OH)D, 24,25-(OH)D, 3-epi-25-(OH)D, and 1,25-(OH)D) were assessed using LC-MS/MS. The 25-(OH)D concentration was calculated based on serum albumin and VDBP levels.

Results: There were no differences in vitamin D metabolites and VMRs between inactive men and between the two groups of athletes. We showed a strong relationship between 25-(OH)D, 25-(OH)D and 24,25-(OH)D, 3-epi-25(OH)D, 24,25-(OH)D:25-(OH)D in each group. Analysis showed that 25-(OH)D, 25-(OH)D inversely associated with 25-(OH)D:24,25-(OH)D, 25-(OH)D:3-epi-25-(OH)D 1,25-(OH)D:24,25-(OH)D ratios in inactive men and athletes (indoor and outdoor).

Conclusions: On the basis of our results, we concluded that regular long-term physical activity has no effect on the concentration of vitamin D metabolites at rest. Furthermore, free vitamin D does not correlate more strongly with vitamin D metabolites and VMRs compared to total.