Vitamin B12 (cyancobalamin) has several important functions in the body, so deficiency can cause a variety of illnesses.

The first function is the maturation of red blood cells (red blood cells that carry oxygen).

The average life span of a red blood cell is 120 days, after which it is destroyed in the spleen. The red blood cell does not have a "clock" which sends it to a "graveyard"... It lives until, through various influences, it changes its shape from a disk to a large ball (megaloblast). Such a "ball" does not pass through the structure of the spleen, gets stuck and is destroyed. Vitamin B12 is what gives the red blood cell its disc shape. If the body lacks this vitamin, the red blood cells will initially appear in an "aged" ball shape. This causes the blood cells to live much shorter than intended and eventually megaloblastic anemia (anaemia) develops.

Second function: involvement in the metabolism of homocysteine (see article "homocysteine"). Homocysteine is an amino acid whose accumulation in the body causes the vascular wall to become "loose". This condition manifests itself in a variety of ways, depending on the organ affected (from a complication of diabetes to pregnancy termination). Cyancobalamin helps homocysteine change its structure and become a non-toxic methionine.

Third function: Immune function. Deficiency of the vitamin causes immune cells neutrophils to have less strength in fighting microorganisms (hypersegmented neutrophils).

Fourth function: to ensure the functioning of the nervous system. B12 is essential for the formation of the myelin sheath of nerve cells. In other words the formation of new nerve fibres or the repair of old ones cannot be done without this vitamin.

The most common cause of vitamin B12 deficiency is gastric diseases (e.g. gastritis). The stomach secretes a special substance ("Castle Factor") that binds to the vitamin and prevents the acidic environment of the stomach from destroying it. If it is not produced or is produced in small amounts, the cyancobalamin is destroyed by gastric hydrochloric acid, which leads to all of the above conditions in the body.