The disulfide bridge between Cys and Cys is essential for maintaining the peptides bioactive conformation
Neuroimaging (MRI of the spinal cord) may occasionally be warranted to exclude other pathology or to demonstrate the characteristic changes of subacute combined degeneration, though this is not routinely required for diagnosis
Statins also deplete it, which is a real concern for people on those drugs Urolithin A: produced when gut bacteria metabolize pomegranate compounds
Kuta J, Smetanov S, Benov D, Koristkov T, Macht J (2016) Urinary stones as a novel matrix for human biomonitoring of toxic and essential elements
Andrew Huberman: I also, I'm glad that you're mentioning skin as the major kind of interface between the environment and vitamin D synthesis because a lot of people think of skin as just a protective sheath around us or something to adorn ourselves with, earrings or tattoos or whatever