Relation between Vitamin B12 Levels and Smell Affection in COVID-19 Patients

Introduction Olfactory and gustative alterations are frequent in the initial stages of the COVID-19 infection. Vitamin B12 deficiency has been linked to olfactory dysfunction. Objective The present study aimed to assess the relationship between vitamin B12 levels and smell affection in COVID-19 patients. Methods The present study included 201 laboratory-confirmed COVID-19 patients. Smell affection was assessed using self-rated olfactory function. Serum vitamin B12 levels were assessed using commercial enzyme-linked immunosorbent assay (ELISA) kits. Results According to the smell function assessment, the patients were classified into three categories: normal osmesis ( n = 77), hyposmia ( n = 49), and anosmia ( n = 75) ( Fig. 1 ). Four weeks later, 195 patients (97.0%) had their normal smell function restored. The remainder 6 patients included 4 anosmic and 2 hyposmic patients. Patients with hyposmia or anosmia had significantly lower vitamin B12 levels when compared with patients with normal osmesis (median [IQR]: 363.0 [198.0–539.0] versus 337.0 [175.0–467.0] and 491.0 [364.5–584.5] pg/ml, respectively, p < 0.001). Conclusion Vitamin B12 appears to have some contribution to smell affection in patients with COVID-19 infection.