Riboflavin also plays a role in thyroxine metabolism, and its deficiency may contribute to mental illness, because riboflavin activates vitamin B6, leading to lower thyroxine levels, reduced hypothalamic serotonin synthesis, and decreased levels of S-adenosylmethionine (SAMe), because of disrupting the folate-methylation pathways involved in SAMe synthesis, all of which are associated with antidepressant effects, consequently, low levels of these compounds may cause depression ( Figure 4 ) (48, 49)
Am J Physiol Endocrinol Metab 2013, 305: E1367E1374
No Tolerable Upper Intake Level (UL) has been established for B12, due to its This threshold has not been set for B12 because your body excretes whatever it doesnt use through your urine
What tends to happen, though, is that people chase higher doses when consistency would've done more