Background: In obesity, low levels of vitamin D (VD) and vitamin B12 (VB12) may be the result of different pathophysiological mechanisms, but the possible association between them has not been defined yet. The aim of this cross-sectional analysis was to investigate the possible relationship between serum 25-hydroxyvitamin D (25(OH)D) and VB12 levels in middle aged women.
Methods: In 80 women, we indirectly evaluated body composition and body volumes [extracellular fluid volume (ECV) and total body water (TBW)] by anthropometric and bioelectrical impedance analysis. Vitamin D and VB12 status was assessed by laboratory measurement [serum 25(OH)D levels by electrochemiluminescent immunoassay; VB12 by chemiluminescent microparticle immunoassay].
Results: Obese women were mostly VD deficient [25(OH)D below 50 nmol/L; 40/50, 80%]. Also, among obese we observed presence of VB12 deficiency [VB12 below 148 pmol/L; 13/50, 26%) and marginal depletion of VB12 level (marginal VB12 status 148-221 pmol/L; 20/50, 40%). All anthropometric indicators of obesity, ECV and TBW were significantly associated with both, 25(OH)D and VB12 (P<0.001) levels. In univariate regression analysis serum level of 25(OH)D was significantly associated with VB12 levels (R2=0.170, P<0.001). In regression models, 25(OH)D was significantly associated with VB12 level, independently of fat mass and extracellular fluid volume.
Conclusions: Obesity may negatively affect VB12 level, indirectly, by reducing 25(OH)D level in middle aged women.