How are Vitamin D 25-OH and Sport related?

The relationship between vitamin D (25-OH) and sport is not fully established. Vitamin D is essential for bone health and immune function, and some evidence suggests adequate levels may support muscle function, recovery, and athletic performance. However, most data come from observational or mechanistic studies; randomized controlled trials show small or inconsistent effects. Deficiency (25-OH < 20 ng/ml) may impair recovery and increase injury risk, but supplementation in replete individuals offers no clear benefit. Athletes with limited sun exposure (e.g., indoor sports) or darker skin are at higher risk for low levels. A blood test is recommended before high-dose supplementation. Evidence is moderate and does not support blanket recommendations. Marketing often overstates benefits. Caveat: VDR gene variants (e.g., rs2228570) have minor effects and do not replace direct measurement.