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

Vitamin B12 (cobalamin) is essential for neurodevelopment, particularly during pregnancy and early childhood. Its deficiency has been implicated in neurological disorders, but also autism spectrum disorder (ASD). Maternal B12 levels influence fetal brain development, and inadequate intake may increase ASD risk. Postnatally, insufficient cobalamin in a child’s diet could further impact neurodevelopment. One mechanism linking B12 deficiency to ASD involves its role in gut microbiota balance. Dysbiosis, common in ASD, is associated with low-grade inflammation and gut-brain axis disruptions. Additionally, B12 is crucial for neurotransmitter metabolism, including serotonin and dopamine synthesis, and for neuronal myelination—both essential for cognitive and behavioral function. Despite emerging evidence, the link between B12 and ASD remains inconclusive due to inconsistent findings. Research suggests B12 may serve as a biomarker for disease progression and treatment response. However, most studies rely on single-time-point measurements, failing to account for individual variability and external influences such as diet and environment. Longitudinal studies are needed to clarify whether early B12 supplementation could mitigate ASD symptoms. Identifying children at risk of deficiency and promoting maternal and early-life nutrition may aid in prevention and intervention.