Research

Hormonal

Vitamin D deficiency (serum 25(OH)D < 20 ng/mL) is associated with a significantly increased risk of sleep disorders, including poor sleep quality, short sleep duration, and daytime sleepiness.

This paper establishes a strong observational link between low Vitamin D levels and poor sleep. However, it does not prove that taking Vitamin D supplements will fix your sleep, as the evidence comes from observational studies, not controlled trials. If you suspect you are deficient, consult a doctor for testing. Do not self-prescribe high-dose Vitamin D solely for sleep improvement based on this paper alone, as the causal mechanism is not yet confirmed by RCTs.

ModerateSupportsMEDIUM confidence
participants with vitamin D deficiency (VDD) had a significantly increased risk of sleep disorders (OR: 1.50, 95% CI: 1.31, 1.72)... Subgroup analysis showed that VDD also was associated with poor sleep quality (OR: 1.59, 95% CI: 1.23, 2.05), short sleep duration (OR: 1.74, 95% CI: 1.30, 2.32), and sleepiness (OR: 1.36, 95% CI: 1.12, 1.65).
Qi Gao et al. · Nutrients · 2018

Why this rating

The evidence is based on a meta-analysis of observational studies (cross-sectional, case-control, cohort). The authors explicitly state that causal association cannot be established and call for RCTs.

Source

The Association between Vitamin D Deficiency and Sleep Disorders: A Systematic Review and Meta-Analysis

Qi Gao et al. · Nutrients · 2018

DOI 10.3390/nu10101395

Meta-analysis · 9 studiesCited 190×
Read the paper
DOI resolved against Crossref · corpus check 2026-06-10

This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →