Here is a short explanation of the mechanism by which the normal body acquires this important substance.
It will be apparent that with our drastically cut-down stomach tissue this process can be impaired,resulting in the need for supplementation by oral &/or injectable routes.
There is the possibility that incipient p.anaemia might provide one explanation for the fatigue/exhaustion that so many of us experience from time to time.
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Intrinsic Factor
Intrinsic factor is a glycoprotein secreted by parietal (humans) or chief (rodents) cells of the gastric mucosa (Stomach Lining). In humans, it has an important role in the absorption of vitamin B12 (cobalamin) in the intestine, and failure to produce or utilize intrinsic factor results in the condition pernicious anaemia.
Dietary vitamin B12 is released from ingested proteins in the stomach through the action of pepsin and acid. It is rapidly bound by one of two vitamin B12-binding proteins that are present in gastric juice; at acid pH, these binding proteins have a greater affinity for the vitamin than does intrinsic factor. In the small intestine, pancreatic proteases digest the binding proteins, releasing vitamin B12 which then becomes bound to intrinsic factor. Finally, there are receptors for intrinsic factor on the ileal mucosa (Lining of the Ileum) which bind the complex, allowing vitamin B12 to be absorbed into portal (Vein) blood.
In all mammals, vitamin B12 is necessary for maturation of erythrocytes (Red Blood Cells), and a deficiency of this vitamin leads to development of anaemia. Since efficient absorption of vitamin B12 in humans depends on intrinsic factor, diseases which decrease the secretion of intrinsic factor (e.g. atrophic gastritis), interfere with cleavage of the binding proteins (e.g. pancreatic exocrine insufficiency) or decrease binding and absorption of the intrinsic factor-vitamin B12 complex (e.g. ileal disease or resection) can result in this type of anaemia.
Source :- Colorado State University/Mededu
Spelling Anglicised
COMMENT-
Can we still produce enough of the following for the process to be carried out effectively ?
1) Sufficient Hydrochloric Acid ? (PPI's ?)
2) Sufficient Pepsin ?
3) Sufficient of the two Binding Proteins ?
4) Sufficient Intrinsic Factor ?
