https://articles.mercola.com/sites/articles/archive/2019/02/07/b-vitamins-cognitive-function.aspx?utm_source=dnl&utm_medium=email&utm_content=art1&utm_campaign=20190207Z1_UCM&et_cid=DM265621&et_rid=539121791

This Deficiency Often Leads to Brain Shrinkage, Psychosis and Alzheimer's