Vitamin B12 and Autism Spectrum Disorder: A Review of Current Evidence

Abstract

Vitamin B12 (cobalamin) plays a crucial role in neurodevelopment, particularly during pregnancy and early childhood. It is essential for DNA synthesis, red blood cell formation, and nervous system function. Maternal B12 levels are particularly important, as they influence fetal brain development. Inadequate maternal intake during pregnancy may lead to altered neurodevelopmental trajectories and increase the risk of ASD. Postnatally, insufficient dietary cobalamin in infants and young children could further contribute to cognitive and behavioral impairments. One potential mechanism linking low B12 levels to ASD involves its role in the gut microbiota balance. Dysbiosis, commonly observed in individuals with ASD, is associated with increased gut permeability, low-grade inflammation, and disruptions in the gut-brain axis, all of which may contribute to ASD symptoms. Additionally, B12 is essential for neurotransmitter metabolism, particularly in the synthesis of serotonin and dopamine, which regulate mood, cognition, and behavior. Cobalamin also plays a key role in neuronal myelination, which ensures efficient signal transmission in the nervous system. Disruptions in these processes could underlie some of the cognitive and behavioral features associated with ASD. Despite growing evidence, the link between B12 and ASD remains inconclusive due to inconsistent findings across studies. Research suggests that B12 levels may serve as a potential biomarker for disease progression and treatment response. However, many studies rely on single-time-point measurements, failing to account for individual variability, genetic predispositions, dietary intake, and environmental factors, all of which can influence B12 levels and ASD risk. Further longitudinal studies are needed to clarify this relationship.

Keywords: ASD; autism spectrum disorder; cobalamin; dysbiosis; microbiome; supplementation; vitamin B12.

Figure 1

The role of vitamin B12 in neurodevelopment. Vitamin B12 acts as a cofactor for methylmalonyl-CoA mutase (MUT). MUT uses vitamin B12 in the form of adenosylcobalamin to facilitate the conversion of L-methylmalonyl-CoA to succinyl-CoA, which then enters the tricarboxylic acid (TCA) cycle, a key process in myelination. Cobalamin also plays a role as a methyl donor, which facilitates the correct methylation of DNA, RNA, histones and proteins. Vitamin B12 is involved in the synthesis and regulation of dopaminergic (DA) and serotonergic (5-HT) neurotransmitters.