6 Steps of Vitamin B12 Absorption, in a Nutshell
Patients of vitamin B12 deficiency from pernicious anemia often wonder exactly what gets in the way of vitamin B12 absorption- why is it that you can eat rich sources of vitamin B12 found in beef, fish, and chicken, and still suffer from chronic fatigue, muscle pain, memory loss, and disorientation from low vitamin B12 levels?
How do we absorb vitamin B12?
Vitamin B12 absorption begins in the mouth. When you eat animal-based foods such as lean beef, fish, and poultry, an R-protein in your saliva called haptocorrin, also known as transcobalamin-1, binds to the vitamin B12, creating vitamin B12-haptocorrin complex.
Step 2 of vitamin B12 absorption takes place in the esophagus, where the new vitamin B12-haptocorrin duo travels to the stomach.
In step 3, the vitamin B12 you ate is protected from caustic elements of the stomach, such as hydrochloric acid, which is produced by the parietal cells of the stomach. The stomach also produces intrinsic factor (IF), a protein which will be crucial in binding and digesting vitamin B12.
Next, in step 4 of vitamin B12 absorption, intrinsic factor and vitamin B12-haptocorrin travel from the stomach to the duodenum, the uppermost section of the small intestine, where vitamin B12 then separates from the R-protein and binds with intrinsic factor, forming a new compound- IF-Vitamin B12 complex.
In step 5, upon reaching the bottommost part of the small intestines, the ileum breaks down intrinsic factor, and releases vitamin B12, which then binds to transcobalamin-2.
Finally, in step 6, vitamin B12 is directed to the blood supply, the liver, bone marrow, or to several other cells of the body which require vitamin B12 for healthy maintenance.
What causes vitamin B12 malabsorption?
This will be covered in the tomorrow’s post…
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