VITAMIN B12 DEFICIENCY AND DEPRESSION: WHAT IS THE MECHANISM?
Author(s): Gregory Russell-Jones
Vitamin B12 Deficiency has often been linked to depression, which conceptually has been assumed was due to lower production of serotonin. We have compared urinary Methylmalonic acid levels (a marker for vitamin B12 deficiency) with the neurotransmitter metabolites of the serotonin/kynurenine pathway and have found a direct correlation between the Kynurenic Acid and Quinolinic Acid metabolites and MMA levels. With increasing MMA there was also a gradual increase in levels of the serotonin metabolite, 5-Hydoxyindole acetic acid. The data suggests that rather than there being a decrease in production of serotonin in vitamin B12 deficiency, there is actually an increased production of serotonin and the tryptophan metabolites Kynurenic acid and Quinolinic Acid, potentially leading to down-regulation of serotonin receptors, potentially being the cause of depression. ASEAN Journal of Psychiatry, Vol. 23(S2) April, 2022; 1-9.