The human body stores several years’ worth of vitamin B12,
so nutritional deficiency of this vitamin is extremely rare. Elderly are the
most at risk. However, deficiency can result from being unable to use vitamin
B12. Inability to absorb vitamin B12 from the intestinal tract can be caused by
a disease known as pernicious anemia. Additionally, strict vegetarians or
vegans who are not taking in proper amounts of B12 are also prone to a
deficiency state.
Vitamin B12 is a water-soluble vitamin that is naturally
present in some foods, added to others, and available as a dietary supplement
and a prescription medication. Vitamin B12 exists in several forms and contains
the mineral cobalt, so compounds with vitamin B12 activity are collectively
called “cobalamins”. Methylcobalamin and 5-deoxyadenosylcobalamin are the forms
of vitamin B12 that are active in human metabolism.
The B12 molecule was first isolated in its cyano-form
in 1948 and was then identified as the
active component of the “extrinsic factor” proposed by Castle. The chemical structure
of the B12 molecule was later confirmed, using xray crystallography by Dorothy
Hodgkin in 1956. She was subsequantly awarded the Nobel Prize in chemistry for
her significant findings.
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