Castle´s extrinsic factor
Animal protein factor
What It Is Vitamin
B12 is one of eight water-soluble B vitamins. Vitamin B12 is the largest and most complex of all the vitamins.
Role in the human body
Vitamin B12 is necessary for the formation of blood cells, nerve sheaths and various proteins. It is therefore essential for growth, normal function of the blood, nervous and immune systems. It is also involved in energy production from fat and carbohydrate metabolism.
Where It Is Found
Vitamin B12 is produced exclusively by bacteria in the digestive tract of animals. Therefore, animal protein products are the main source of vitamin B12, in particular organ meats such as liver and kidney. Other good sources are fish, shellfish, eggs and dairy products.