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Vitamin B12
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Vitamin B12, also called cobalamin, is a water-soluble vitamin, meaning it dissolves in water. We get it from animal products such as red meat, dairy and eggs.
Eating it is not enough for the body to use it. To be absorbed in the terminal ileum, the last stretch of the small intestine, it needs a partner: intrinsic factor, which is made by the parietal cells of the stomach. Once inside the body, B12 works as a cofactor, a helper that enzymes need to do their job. Those enzymes take part in making three things: DNA, fatty acids and myelin, the layer that wraps around nerves.
Any B12 the body does not need right away is stored in the liver. The liver is a pantry: it empties when it stops being restocked. When absorption fails over a prolonged period, that pantry runs empty and deficiency sets in, which can cause symptoms in the blood and in the nervous system.
In brief
Vitamin B12, or cobalamin, is a water-soluble vitamin obtained from animal products such as red meat, dairy and eggs.
It is absorbed in the terminal ileum thanks to intrinsic factor from gastric parietal cells, and it acts as a cofactor for enzymes involved in making DNA, fatty acids and myelin.
The liver holds large reserves of it; if absorption fails for a long time, that reserve runs out and the resulting deficiency can cause hematologic and neurologic symptoms.
The liver is a pantry: it empties when it stops being restocked.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingVitamin B12 Deficiency, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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