BACKGROUND/AIM: High-dose vitamin D supplementation is increasingly used to achieve extraskeletal effects, but its safety regarding mineral metabolism remains under discussion. This study assessed the effects of vitamin D on serum calcium, magnesium, and parathyroid hormone (PTH) concentrations in young healthy individuals. MATERIALS AND METHODS: Sixty-five healthy volunteers received cholecalciferol drops in doses ranging from 1,000 to 8,000 IU/day across two winter seasons. Serum concentrations of 25-hydroxyvitamin D 25(OH)D, calcium, magnesium, and PTH were measured at defined intervals. RESULTS: Supplementation resulted in a dose-dependent increase in serum 25(OH)D, reaching a maximum of 208.5 nmol/l. Despite the high intake, all measured parameters remained within physiological ranges. A significant inverse association between 25(OH)D and PTH levels confirmed physiological suppression of PTH at higher vitamin D concentrations, though all values stayed within reference limits. CONCLUSION: The absence of clinically relevant disturbances in calcium, magnesium, or PTH levels supports the safety of high-dose vitamin D supplementation when appropriately monitored in young healthy adults, even at the upper limits of therapeutic dosing. These findings highlight the need for further research to delineate the long-term effects of high-dose vitamin D supplementation on mineral metabolism across diverse patient populations.
Králová et al. (2026) studied this question.