Plasma Vitamin B12 May Be a Misleading Biomarker among Children with Severe Acute Malnutrition: An Observation from Mwanza, Tanzania

Abstract

Background: Vitamin B12 deficiency is related to impaired neurodevelopment and anemia and is a global health concern in children with severe acute malnutrition (SAM). Objectives: We investigated vitamin B12 status in children with SAM and among non-malnourished comparisons and assessed the validity of the plasma vitamin B12 assay. Methods: This study was part of a pilot study of a nutritional intervention. We measured plasma concentrations of vitamin B12, methylmalonic acid (MMA), total haptocorrin (HC), and total transcobalamin (TC) in children with SAM before and after 8 wk of nutritional treatment and at a single timepoint in non-malnourished children. Results: We included 82 children with SAM and 82 children without acute malnutrition. Plasma vitamin B12 was higher in children with SAM at enrollment than in controls (median 647 compared with 411 pmol/L) and declined after treatment (median 469 pmol/L). Baseline plasma vitamin B12 was particularly high in children with edematous SAM compared to those without edema (P = 0.050). In contrast, plasma MMA was higher in those with SAM, reflecting lower vitamin B12 function (median 220 compared with 170 nmol/L), and declined after treatment (median 190 nmol). HC was positively correlated with vitamin B12 concentration (P < 0.001) and was also higher in children with SAM than in comparison children (median 959 compared with 789 pmol/L), decreasing after treatment (median 815 pmol/L). TC was higher in children with SAM than comparisons but did not decrease after treatment. Overall, 23% of children with SAM had MMA concentrations suggesting vitamin B12 deficiency compared to 4.5% of non-malnourished children. Conclusions: In contrast to our initial expectations, we found that plasma vitamin B12 was higher in children with SAM, especially those with edema. However, analysis of MMA revealed lower vitamin B12 function in malnourished children and improvement after treatment, warranting caution in the interpretation of plasma vitamin B12 in SAM. Elevated HC in SAM may explain high vitamin B12 concentration, but the cause of elevated HC needs further investigation.