Dietary habits and nutrients have been associated with migraine. The present study comprises a meta-analysis of observational studies evaluating serum levels of 25-hydroxyvitamin D (25(OH)D) in patients with migraine and healthy controls.

MEDLINE and Cochrane databases were comprehensively searched. References from retrieved observational studies, reviews and meta-analyses were manually screened. Quality assessment was performed based on the Newcastle-Ottawa Scale. 25(OH)D concentrations were assessed by estimates of mean differences (MD) and their precision [95% confidence intervals (95% CIs)]. Random effects (RE) or fixed effects (FE) model was used based on heterogeneity among trials (homogeneity determined when PQ>0.1 and I2<50%). Publication bias was assessed by funnel plots.

Eight studies were included in the primary analysis, while nine studies were involved overall (in primary and secondary analyses). Serum levels of 25(OH)D were determined significantly lower in migraine patients (n=952) in comparison with healthy controls (n=8013) [eight studies, PQ<0.1, I2=94%, RE model MD=−4.11, 95% CI=(−6.48, −1.74)]. Secondary analysis revealed no difference between patients with migraine (n=269) compared to patients with other primary headache disorders (n=223) [three studies, PQ=0.51, I2=0%, FE model MD=−0.15, 95% CI=(−1.57, 1.05)], as well as between patients with tension type headache (n=295) in comparison with healthy controls (n=267) [three studies, PQ<0.1, I2=96%, RE model MD=−7.11, 95% CI=(−15.50, 1.27)].

25(OH)D concentration is lower in patients with migraine than healthy individuals. In view of this finding, investigation of the effect of vitamin D supplementation in patients suffering from migraine is warranted.