Vitamin B12 is needed in microscopic amounts, but a shortage can have major effects on health and energy. The vitamin was first linked to a lifesaving liver treatment for pernicious anemia nearly 100 years ago. Today, researchers are finding that B12 may also help keep cellular powerhouses called mi tochondria functioning properly. This could explain why some people experience fatigue and brain fog even before traditional signs of deficiency show up. ...read more read less