I don't give much credit to this article. I do think some vitamins are junk. There are many brands that are good. My Naturapathic doctor did a blood test that showed I have a defective gene where I can't convert folic acid to be absorbed by the body. I now take L-5MTHF and vitamin B12 shots.
My mom asked her family doctor about this defective gene and he blew her off and said if she did have it nothing could be done about it. Folic acid deficiency can include: macrocytic, anemia, fatigue, irritability, peripheral neurophy,tendon hyper-reflexivity, restless legs syndrome, diarrhea, weight loss, insomnia, depression, dementia, cognitive disturbances, and psychiatric disorders.
Many conditions are caused and could be treated with vitamins and supplements.