Does the levels of vitamin D correlate with the levels of vitamin B12 and ferritin in fibromyalgia?

Background/Aim: Considering the effects of inflammation on fibromyalgia and the small intestine, we hypothesize that vitamin D deficiency may contribute to inflammation and affect vitamin B12 and ferritin levels in patients with fibromyalgia. The objectives were: 1) to compare the levels of vitamin D, vitamin B12, and ferritin in patients with fibromyalgia and patients who have local painful conditions, and 2) to evaluate the correlation of vitamin D levels with vitamin B12 and ferritin levels. Methods: The records of 299 patients with fibromyalgia (274 female, 25 male) and 128 patients with local painful conditions (114 female, 14 male) between April 2019 and 2020 were examined, including measurements of 25-hydroxy vitamin D, vitamin B12, ferritin, erythrocyte sedimentation rate, and C-reactive protein. Results: The levels of 25-hydroxy vitamin D were low in both groups, with levels below 30 ng/ml in 90.3% of all patients. However, there was no significant difference in vitamin B12 and ferritin levels between the two groups, and the levels of these markers were within normal limits in both groups. Correlation analysis showed that vitamin D levels were significantly correlated with vitamin B12 (P<0.001, r=0.211) and ferritin (P=0.005, r=0.337) levels in patients with fibromyalgia but not in the other group. Conclusion: Consistent with our hypothesis, an association was found between vitamin D levels and vitamin B12 and ferritin levels in fibromyalgia. However, this correlation was not found in patients with local painful conditions.