Vitamin B12 is an important nutrient.
A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts . Vitamin B12 , also called cobalamin , is a water-soluble vitamin that has a key role in the normal functioning of the brain and nervous system , and the formation of red blood cells . Due to impairment of vitamin B12 absorption during aging , people over age 60 are at risk of deficiency .