CALCA and Headache: In the present research, it was found that patients in the intervention group had significantly lower S25OHD levels, and on the other hand, a slightly higher serum CGRP levels at baseline; however, supplementation with the vitamin resulted in significant increment of S25OHD and reduction of CGRP, though we did not find any dose-response correlation throughout the trial between either of headache related parameters (e.g. frequency of headache days, MIDAS score or serum CGRP levels) and S25OHD.