Myths vs facts: Vitamin D 25-OH and Fruchtbarkeit

Myth: Vitamin D (25-OH) is a magic bullet for fertility. Fact: Adequate vitamin D levels are important for overall health, but the direct causal evidence for fertility is limited. Observational studies link low 25-OH levels to reduced fertility in both women and men, yet randomized controlled trials show mixed results. Genetic variants in the VDR gene (e.g., rs1544410) may modulate vitamin D action, but their clinical relevance for fertility remains unclear. DNA tests for such variants cannot replace a direct blood measurement of 25-OH. Caution: correcting a deficiency is sensible, but megadosing (e.g., >4000 IU/day without medical supervision) can be toxic. The evidence is primarily observational; effect sizes are moderate and not universal. Bottom line: vitamin D is one piece of the fertility puzzle, not a standalone solution.