Vitamin B-12 Is Like Magic For Your Brain — But Many People Are Low Or Deficient In It. The nutrient plays a role in memory, focus, mental health and so much more https://www.huffpost.com/entry/vitamin-b12-brain-health_l_6977a7bae4b01cc3c1ad545f When B-12 levels drop too low, the brain is one of the first places you might see the effects. Vegetarians and vegans and people taking metformin and acid-suppressing drugs like proton pump inhibitors over long periods of time may also develop a B-12 deficiency and should be monitored