Vitamin B12 and brain shrinkage

Do keep in mind that Vitamin B12 is so important for the nervous system that low levels accelerate neurodegeneration to the degree that the brain shrinks markedly, as described in this paper published in the journal Neurology. [A cautionary note for any doctors reading this post: brain volume loss was, surprisingly, not associated with high levels of methylmalonic acid or homocysteine. The association was with serum B12 <308 pmol/L, low levels of holotranscobalamin and transcobalamin saturation.]