Summary: In a double-blind trial in male ultramarathon runners, a single 150,000 IU dose of vitamin D taken 24 hours before the race shifted post-race bone turnover markers favourably, raising a bone-formation marker and lowering resorption and stress markers compared with placebo.
PICO Summary
| Element | Detail |
|---|---|
| Population | 35 semiprofessional male mountain-ultramarathon runners; double-blind RCT, Poland. |
| Intervention | Single high dose of vitamin D3 (cholecalciferol 150,000 IU) in oil, 24 hours before the run (n=16). |
| Comparison | Placebo 24 hours before the run (n=19); blood at 24 h before, immediately after, and 24 h after. |
| Outcome | 25(OH)D rose in both groups, more with supplementation (147% vs 85% at 24 h post-race). The bone-formation marker PINP rose more in the supplemented group immediately after; CTX, PTH, sclerostin, and procalcitonin were higher in the placebo group 24 h post-race, indicating attenuated resorption and stress responses with vitamin D. No adverse effects. |
Single high-dose vitamin D before an ultramarathon
Double-blind RCT · male ultramarathon runners · acute pre-race dose
A single 150,000 IU vitamin D dose 24 h before an ultramarathon raised 25(OH)D more (147% vs 85%) and shifted bone turnover markers favourably, with higher formation (PINP) and lower resorption and stress markers than placebo. Surrogate markers only, not clinical bone outcomes.
Expert Commentary
This is a neat mechanistic study with a coherent endocrine rationale, even if its practical message is more cautious than its headline. Prolonged endurance exercise reliably spikes bone resorption, partly through a rise in PTH as the body defends serum calcium, and the proposed fix here is elegant: acutely optimise vitamin D so calcium absorption is sufficient, blunting the PTH-driven resorption and tilting the formation-to-resorption balance favourably. The marker pattern fits that story well, higher PINP formation and lower CTX, PTH, and sclerostin, with the sclerostin signal hinting at a genuinely anabolic effect rather than mere damage limitation. My reservations are about both scale and translation. With only 35 male runners and biochemical surrogates rather than fracture or bone-density outcomes, this cannot show that the favourable marker shifts prevent injury, and the single 150,000 IU mega-dose, while uneventful here, is unconventional and risks hypercalcaemia if repeated. Can I use this with my patients? Mostly as physiology rather than prescription. It reinforces ensuring adequate baseline vitamin D in athletes through conventional regular dosing, while I would treat pre-event mega-dosing as experimental and not recommend it outside supervised study.
References
Stankiewicz B, Kochanowicz A, Brzezińska P, et al. Single high-dose vitamin D supplementation impacts ultramarathon-induced changes in serum levels of bone turnover markers: a double-blind randomized controlled trial. J Int Soc Sports Nutr. 2025;22(1):2561661. doi:10.1080/15502783.2025.2561661