Vitamin B12 (cobalamin) is important in the formation of all cells in the body, especially red blood cells and the covering of nerve cells (myelin). The body needs myelin for nerves to function properly.

Vitamin B12 is found in animal products such as meat, shellfish, milk, cheese, and eggs.

People who are vegan and don't eat any animal products are at risk for vitamin B12 deficiency. They need a vitamin supplement containing vitamin B12.