AUTHOR=Książek Anna , Zagrodna Aleksandra , Lombardi Giovanni , Słowińska-Lisowska Małgorzata 

TITLE=Seasonal changes in free 25-(OH)D and vitamin D metabolite ratios and their relationship with psychophysical stress markers in male professional football players

JOURNAL=Frontiers in Physiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2023.1258678

DOI=10.3389/fphys.2023.1258678

ISSN=1664-042X

ABSTRACT=<p><bold>Introduction:</bold> Novel markers of vitamin D status are currently being investigated, including free 25-(OH)D (25-(OH)D<sub>F</sub>) and the vitamin D metabolite ratio (24,25-(OH)<sub>2</sub>D<sub>3</sub>:25-(OH)D<sub>3</sub>; VMR). The VMR may provide additional functional information on vitamin D metabolism in athletes. Therefore, the main objective of the current study was to evaluate 25-(OH)D<sub>F</sub>, bioavailable 25-(OH)D (25-(OH)D<sub>B</sub>), VMR, and psychophysical stress markers during different training periods over a half-season. The second aim was to assess the association between vitamin D binding protein (VDBP), total and free 25-(OH)D, VMRs, and psychophysical stress markers in professional football players. Moreover, we examined the relationship between 25-(OH)D<sub>3</sub> and vitamin D metabolites (24,25-(OH)<sub>2</sub>D<sub>3</sub>, 3-epi-25-(OH)D<sub>3</sub>) to determine if training loads in different training periods influenced the vitamin D metabolome.</p><p><bold>Methods:</bold> Twenty professional football players were tested at six different time points across half a year (V1—June; V2—July; V3—August; V4—October; V5—December; V6—January).</p><p><bold>Results:</bold> Analyses indicated a significant seasonal rhythm for VDBP, and total 25-(OH)D (25-(OH)D<sub>T</sub>), 25-(OH)D<sub>B</sub>, 24,25-(OH)<sub>2</sub>D<sub>3</sub>, 3-epi-25-(OH)D<sub>3</sub>, 25-(OH)D<sub>3</sub>:24,25-(OH)<sub>2</sub>D<sub>3</sub>, and 24,25-(OH)<sub>2</sub>D<sub>3</sub>:25-(OH)D<sub>3</sub> VMRs throughout the training period. No correlation was detected between 25-(OH)D<sub>T</sub>, 25-(OH)D<sub>B</sub>, 25-(OH)D<sub>F</sub>, vitamin D metabolites, VMRs, VDBP, and ferritin, liver enzymes (aspartate transaminase [AST] and alanine transaminase [ALT]), creatine kinase (CK), cortisol, testosterone, and testosterone-to-cortisol ratio (T/C) in each period (V1-V6). However, there was a strong statistically significant correlation between 25-(OH)D<sub>3</sub> and 24,25-(OH)D<sub>3</sub> in each training period.</p><p><bold>Conclusion:</bold> In conclusion, a seasonal rhythm was present for VDBP, 25-(OH)D<sub>T</sub>, 25-(OH)D<sub>B</sub>, vitamin D metabolites (24,25-(OH)<sub>2</sub>D<sub>3</sub>, 3-epi-25-(OH)D<sub>3</sub>), and VMRs (25-(OH)D<sub>3</sub>:24,25-(OH)<sub>2</sub>D<sub>3</sub>, 25-(OH)D<sub>3</sub>:3-epi-25-(OH)D<sub>3</sub>). However, no rhythm was detected for 25-(OH)D<sub>F</sub> and markers of psychophysical stress (ferritin, liver enzymes, CK, testosterone, cortisol, and T/C ratio). Moreover, the relationships between free and total 25-(OH)D with psychophysical stress markers did not demonstrate the superiority of free over total measurements. Furthermore, training loads in different training periods did not affect resting vitamin D metabolite concentrations in football players.</p>