This vitamin is essential for the normal formation of red blood cells
and proper functioning of nerves
and nervous system. A deficiency in vitamin B12 decreases the production of red blood cells leading to anaemia.The treatment of this deficiency is either oral ingestion of vitamin B12 or injections. He should consume a diet rich in meat, milk, cheese, and eggs, , leafy green vegetables, citrus fruits, , fortified breads and cereals which are rich in vitamin B12 and folic acid.