What benefits are gained from Vitamin B12?

Cells in your stomach secretes something called intrinsic factor. This is needed to take up B12 in your small intestine. From there it is transported to the liver where it is stored, utilized and transported. B12 walks hand in hand with a vitamin called folate or folic acid. B12 is needed for myelination of neurons. That is a covering of the axons that increases the speed of nerve impulses. Folate is needed for proper DNA replication. At last B12 is needed to activate folate. This means that if you have B12 deficiency you will also have folate deficiency.

Since folate is vital for DNA replication the cells will divide as usual, but it will be sluggish and incomplete nuclei material. The cells will be bigger. This happens to all cells, but is first seen in cells with low turn-over time such as red blood cells (120 days). Abnormally big red blood cells are called megaloblastic anemia.

B12 deficiency will impaire your neural system, most importantly the CNS (central nervous system).

This means that a megaloblastic anemia can be cured with folate supplements, but neuronal symptoms can only be cured by B12. If the problem is with the stomach cells secreting the intrinsic factor you will need to bypass that mechanism of the enterohepatic pathway (from the enterocytes in the small intestine to the hepatocytes in the liver). This is done by a shot of B12. If intrinsic factor was the problem, folate deficiency and the anemia will cure itself.