Excessive vitamin B12 concentrations are more common than deficiency in patients with anorexia nervosa: a cross-sectional study.

Abstract

Background: Vitamin B₁₂ is an essential cofactor for one-carbon metabolism. Deficiency of this vitamin is known to cause various physical and neurological conditions. Several guidelines recommend the intake of multivitamin supplements in patients with anorexia nervosa (AN) in order to avoid these conditions. Excessive blood vitamin B₁₂ concentrations have also been reported in patients with AN. This study examines the relationship between blood vitamin B₁₂ concentrations and clinical, biochemical, and hematological characteristics in patients with AN.

Methods: This retrospective study analyzed data from 71 Japanese female patients with AN. Biological and hematological data were measured before nutritional therapy. Spearman's rank correlation, Fisher's exact test, Mann-Whitney U test, and binary logistic regression analysis were used to explore the relationships between vitamin B₁₂ concentrations and other variables.

Results: The blood vitamin B₁₂ concentrations of 2 patients were below the normal range, while 22 had concentrations exceeding the normal range. The remaining 47 patients had concentrations within the normal range. In the Spearman's rank correlation analyses, significant positive correlations of vitamin B₁₂ concentrations were found with liver enzymes, i.e., aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase, age, and blood urea nitrogen, whereas a negative correlation was found with body mass index (BMI). Binary logistic regression analysis showed that the high vitamin B₁₂ group was linked with higher alanine aminotransferase, total protein, creatinine, and age, but not BMI.

Conclusions: This study demonstrated that excessive vitamin B₁₂ concentrations are more prevalent than deficiency in patients with AN, suggesting that the routine administration of vitamin B₁₂ to patients with AN should be reconsidered. Elevated vitamin B₁₂ concentrations might be associated with starvation-induced autophagy in the liver. Its potential role in physical complications warrants further investigation.