The effect of an acute bout of exercise on circulating vitamin D metabolite concentrations: a randomised crossover study in healthy adults

The effect of acute exercise on circulating concentrations of vitamin D metabolites is unclear. To address this knowledge gap, we examined the effect of a bout of treadmill-based exercise versus rest on circulating concentrations of 25(OH)D₃, 25(OH)D₂, 3-epi-25(OH)D₃, 24,25(OH)₂D₃, 1,25(OH)₂D₃, and vitamin D₂ and D₃ in healthy men and women. Thirty-three healthy adults (14 females, 41 (15) years, body mass index 26.2 (3.7) kg/m², ${\dot{V}}_{O_2\max }$ 36.2 (9.2) ml/kg/min; mean (SD)) completed two laboratory visits involving 60 min of moderate-intensity treadmill exercise (60% ${\dot{V}}_{O_2\max }$ ) versus 60 min of seated rest, both in an overnight fasted-state, as part of a randomised crossover design. Venous blood samples were drawn at baseline, immediately (0 h), 1 h and 24 h after the exercise or rest-period. There was a significant time × trial interaction effect for total circulating 25(OH)D (P = 0.0148), 25(OH)D₃ (P = 0.0127) and 1,25(OH)₂D₃ (P = 0.0226). Immediately post-exercise, 25(OH)D, 25(OH)D₃ and 1,25(OH)₂D₃ concentrations were significantly elevated compared to the control resting condition, and 1,25(OH) ₂D₃ remained significantly elevated 1 h later. Circulating albumin, vitamin D binding protein, calcium and parathyroid hormone were elevated immediately post-exercise. Thus, an acute bout of moderate intensity exercise transiently increases concentrations of circulating 25(OH)D and 1,25(OH)₂D₃ compared to resting conditions. KEY POINTS: Observational studies suggest that acute exercise might change circulating concentrations of vitamin D metabolites, but this has not been investigated using randomised crossover studies and using robust analytical procedures. In this study, we used a randomised crossover design to examine the effect of a bout of treadmill-based exercise (vs. rest) on circulating concentrations of a wide range of vitamin D metabolites in healthy humans. We show that an acute bout of moderate intensity exercise transiently increases concentrations of circulating 25(OH)D and 1,25(OH)₂D₃ compared to resting conditions. These findings indicate that regular exercise could lead to transient but regular windows of enhanced vitamin D biological action.