Myths vs facts: Vitamin D 25-OH and sleep

The claim that vitamin D (25-OH) directly improves sleep is a common myth with only partial scientific support. Vitamin D receptors (VDR) are present in brain regions involved in sleep regulation, and some observational studies link low 25-OH levels to sleep disturbances such as short sleep duration or poor sleep quality. However, the evidence is largely associative, not causal. Randomized controlled trials of vitamin D supplementation in individuals without deficiency generally show no significant sleep improvement. Actual deficiency (25-OH < 30 nmol/L) can contribute to fatigue and sleep issues, but correcting the deficiency does not necessarily resolve all sleep problems. Genetic variants in the VDR gene (e.g., rs2228570) affect vitamin D metabolism, but there is no robust evidence that they directly alter sleep. Consumer DNA tests that report such variants often overstate clinical relevance. Bottom line: vitamin D deficiency may impair sleep, but supplementation in replete individuals has no proven sleep benefit. Blood tests are more reliable than genetic tests.