Last reviewed 02/2022
Dietary vitamin B12 reaches the stomach where it combines with intrinsic factor. The complex is essential for the absorption of the vitamin in the terminal ileum: it is otherwise too massive and fat-insoluble for absorption.
After absorption, it is transported by transcobalmin within plasma. It is stored within the liver; the half-life of this store is several years and minimizes the risk of deficiency states developing.
Vitamin B12 is required as a coenzyme in the synthesis of:
- methionine from homocysteine; vital to DNA, purine and folate production
- succinic acid from methylmalonic acid; involved in fatty acid and amino acid metabolism