Vitamin B₁₂

A water-soluble vitamin that plays a vital role in the activities of several enzymes in the body. Vitamin B is important in the production of the genetic material of cells (and thus in growth and development), in the production of red blood cells in bone marrow, in the utilization of folic acid and carbohydrates in the diet, and in the functioning of the nervous system. Foods rich in vitamin B include liver, kidney, chicken, beef, pork, fish, eggs, and dairy products. Deficiency is almost always due to the inability of the intestine to absorb the vitamin, usually as a result of pernicious anaemia (see anaemia, megaloblastic). Less commonly, deficiency may result from gastrectomy, malabsorption, or veganism. The effects of vitamin B deficiency are megaloblastic anaemia, a sore mouth and tongue, and symptoms caused by damage to the spinal cord, such as numbness and tingling in the limbs. There may also be depression and memory loss. A high intake of vitamin B has no known harmful effects.