Vitamin B12 deficiency
Vitamin D has been under a lot of pressure over the last two years,
but it's not the only nutrient you need to monitor in your body.
Another important one is B12, which helps in the production of red blood cells and DNA
Studies have shown that insufficient B12 levels can cause many problems, from fatigue to dementia.
Dr. Eduardo Villamor, a professor of epidemiology at the University of Michigan,
told Insider that recent research found a higher rate of mental retardation in seniors with vitamin B12 deficiency