Autoimmune Diseases
Though vitamin B12 is mostly absorbed in your small intestine, the digestive process actually occurs in your stomach. The stomach is lined with some cells that are important for absorbing vitamin B12. When you are suffering from autoimmune disease, it would destroy those cells, thus preventing your body from absorbing B12 from foods. Your doctor might find out the cause by taking a simple blood test and then prescribing some drugs or other options to treat it. [8]
