Myths vs facts: Vitamin D 25-OH and longevity

The claim that high 25-OH vitamin D levels directly extend lifespan is largely a myth. Observational data consistently link low 25-OH-D with higher all-cause mortality, but randomized controlled trials (RCTs) in generally healthy populations do not show a clear survival benefit from supplementation beyond correcting deficiency. 25-OH-D is the standard biomarker for vitamin D status, yet optimal levels for longevity remain debated. Excessively high levels can be toxic (hypercalcemia). Fact: correcting a true deficiency is important for bone and immune health, but there is no strong evidence that supraphysiological levels prolong life. The evidence is moderate (observational) and often confounded by lifestyle factors.