Non-significant negative correlations were detected between changes in S25OHD and changes in number of headache days per month (r = − 0.201, P value = 0.094), MIDAS score (r = − 0.176, P value = 0.172), and CGRP levels (r = − 0.144, P value = 0.219) throughout the intervention (Fig. 4). This evidence concerns the gene CALCA and Headache.