Is VDR useful for Müdigkeit?

The question of whether the VDR (Vitamin D Receptor) genotype is useful for fatigue is scientifically debated. Mechanistic evidence suggests that VDR polymorphisms may modulate vitamin D signaling, and low vitamin D levels are associated with fatigue. However, effect sizes of individual VDR variants on fatigue are small and inconsistent across studies. Most positive findings come from observational or small intervention studies, not large RCTs. Direct-to-consumer DNA tests often market VDR as a 'fatigue gene,' which overstates the evidence. In practice, a measured vitamin D deficiency (blood test) is more relevant than genotype. Supplementation in confirmed deficiency can alleviate fatigue, but VDR status alone does not justify specific dosing. Evidence is therefore mechanistic to unclear. Safety note: high-dose vitamin D (>4000 IU/day) without deficiency can be toxic. Conclusion: VDR testing for fatigue is not clinically established; focus should be on measurable vitamin D status and lifestyle factors (sleep, diet, exercise).