Brito A, et al. – This study entails the characterization of the human serum metabolome in subclinical vitamin B–12 deficiency and repletion. In addition to presenting the characteristics of human serum metabolome in vitamin B–12 deficiency and changes that occurred after supplementation, findings also highlighted that vitamin B–12 status was associated with serum metabolic markers of mitochondrial function, myelin integrity, oxidative stress, and peripheral nerve function, including some previously implicated in Alzheimer and Parkinson diseases, as revealed by metabolomics.