Intrinsic factor (IF) is a kind of glycoprotein produced by the parietal cells of the stomach. It has a key role in the absorption of vitamin B12. After binding to intrinsic factor, the vitamin forms a special complex which can be absorbed in the small intensine.
Impaired production of intrinsic factor may be genetically determined, but it occurs equally often due to damage to the gastric mucosa caused by Helicobacter pylori infection. IF synthesis is also seriously inhibited by gastric parietal cell antibodies. IF deficiency limits the absorption of vitamin B12 and may consequently lead to major deficiencies and subsequent diseases.
Purified intrinsic factor, obtained from porcine gastric mucosa, is the most frequent form used in supplementation. It is added to preparations with vitamin B12 or B vitamin complexes to improve cobalamin absorption.