What are the causes of vitamin B12 deficiency?
Pernicious anaemia Normally, when you eat foods with vitamin B12, the vitamin combines with a protein called intrinsic factor in the stomach. The combined vitamin B12/intrinsic factor is then absorbed into the body further down the gut at the end of the small intestine. (Intrinsic factor is made by cells in the lining of the stomach and is needed for vitamin B12 to be absorbed.) Pernicious anaemia is the most common cause of B12 deficiency in the UK. It is due to an ‘autoimmune disease’. The immune system normally makes antibodies to attack bacteria, viruses and other ‘germs’. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body. If you have pernicious anaemia, antibodies are formed against your intrinsic factor, or against the cells in your stomach which make intrinsic factor. This stops intrinsic factor from attaching to vitamin B12, and so the vitamin cannot be absorbed into your body. It is thought that something triggers the im
