Vitamin B12 Deficiency

Excerpt

Vitamin B12 (cobalamin) is a water-soluble vitamin that is derived from animal products such as red meat, dairy, and eggs. Intrinsic factor is a glycoprotein that is produced by parietal cells in the stomach and is necessary for the absorption of B12 in the terminal ileum. Once absorbed, B12 is used as a cofactor for enzymes that are involved in the synthesis of deoxyribonucleic acid (DNA), fatty acids, and myelin. As a result, B12 deficiency can lead to hematologic and neurologic symptoms. B12 is stored in excess in the liver; however, in cases in which B12 cannot be absorbed for a prolonged period (eg, dietary insufficiency, malabsorption, lack of intrinsic factor), hepatic stores are depleted, and deficiency occurs.