Vitamin B12, also known as cobalamin, is a water-soluble
vitamin essential for hematopoietic and neurological functions in the body. It
is obtained primarily from animal sources such as meat and fish. Many breakfastcereals and nondairy beverages such as soymilk are fortified with vitamin B12.
When vitamin B12 from animal foods enters the stomach it is protein bound and
must be released by the action of pepsin in the stomach. It is then attached to
R-proteins and is transported through the duodenum where it is hydrolyzed and
free cobalamin is released. Cobalamin requires intrinsic factor (IF) to attach
to it, in order to be absorbed in the terminal ileum.
This absorption process
is calcium mediated and is the most probable opportunity for met formin induced
vitamin B12 deficiency. Adding supplemental calcium has been shown to mediate
the deficiency in some cases though there is not enough evidence to recommend
calcium supplementation as an effective preventative measure.Vitamin B12 is an essential cofactor in the conversion ofhomocysteine to methionine and regeneration of folate. This is a key step in
the metabolic process that leads to DNA synthesis and formation and protection
of the myelin sheath. Demyelination of nerve endings can lead to peripheral
neuropathy.
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