Vitamin B12, also called cobalamin, is a water-soluble vitamin that is involved in the metabolism of every cell of the human body. It is a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism. Vitamin B12 is produced exclusively by microbial synthesis in the digestive tract of animals. Therefore, animal protein products, in particular organ meats (e.g., liver, kidney), are the source of vitamin B12 in the human diet. Other good sources are fish, eggs and dairy products. A sufficient intake of vitamin B12 is essential for helping the body convert food into glucose, which is used to produce energy, maintain normal nerve cells and regulate, together with vitamin B9 (folate), the formation of red blood cells. Vitamin B12 is widely used as a way to enrich cereal products and certain beverages.