What is the role of vitamin B12 in the human body?

Vitamin B12 plays a crucial role in the human body primarily as a coenzyme. It is essential for the metabolism of fatty acids and amino acids, as well as for the synthesis of DNA and the formation of red blood cells. The coenzyme form of vitamin B12 (methylcobalamin and adenosylcobalamin) is directly involved in critical biochemical processes, including the conversion of homocysteine to methionine, which is vital for the production of myelin—the protective sheath around nerves.

While energy production is a consequence of many metabolic processes in which B12 is involved, it does not provide energy directly; rather, it is fundamental in facilitating pathways that generate energy from food. It does not play a direct role in digestion, which primarily involves enzymes and other substances, nor does it regulate calcium absorption; that function is more closely associated with vitamin D and other factors. Understanding the role of vitamin B12 as a coenzyme highlights its importance in maintaining overall health and supporting vital bodily functions.