Vitamin B-12 also knows as cobalamin, is a water soluble vitamin involved in the metabolism of every cell of the human body. This is needed for nerve tissue health, brain function and the production of red blood cells. It also helps to create and regulate DNA. The human body can store B-12 and any excess or unwanted B-12 is excreted in the urine. Vitamin B-12 is the largest and most structurally complicated vitamin. It is found naturally in animal products such as fish, eggs, meat and dairy products. Deficiency or lack of vitamin B12 can lead to neurological difficulties and anemia.