Vitamin B12 – cobalamin

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General information

Vitamin B12 (or cobolamine) is a water-soluble vitamin, which is mainly found in animal products such as liver or fish and which the human body cannot produce itself. Since it is important for functions such as cell division and cell formation, blood formation and also for the nervous and cardiovascular system, the intake of vitamin B12 through food is essential. Especially vegans who completely refrain from consuming animal products often suffer from an increased risk of vitamin B12 deficiency.

Occurrence and structure

Neither plants nor animals can synthesize vitamin B12, only microorganisms, as they colonize the intestine, are able to do so. Vitamin B12 is found in liver, beef, fish (salmon, herring), cheese, milk or eggs, among other things. The need at Vitamin B12 amounts to approx.

2 – 3μg and is thereby in the comparison to the need at other Vitaminen rather small. For pregnant women, the daily requirement is somewhat higher, about 4μg. Vitamin B12/cobalamin is a complex molecule with cobalt as its central atom.

It contains a corrin ring consisting of four pyrrole rings (tetrapyrrole) and a dimethylbenzimidazone. The cobalt atom can form six bonds. Five of them are already occupied within the molecule, but with one of them it can bind different groups, which it then – this is its function – transfers to different substrates.

By binding e.g. a methyl radical (CH3) to its free binding site on cobalt, cobalamin/vitamin B12 can, for example, transfer such a group to other substrates. For example, during remethylation (reattachment of CH3) of homocysteine to methionine. It can also rearrange certain groups within a molecule, i.e. it serves as a so-called mutase.

Vitamin B12 is essential for many processes and functions in the human body. Vitamin B12 is needed in the following places in the body:

  • Cell division and cell formation: Here it is especially important for blood formation.
  • Formation of hereditary substances: Here vitamin B12 plays an important biochemical role as a coenzyme in the formation of DNA and RNA
  • Nervous system: Vitamin B12 is also needed for the formation of myelin sheaths (fat cells that surround nerve fibers). Studies have shown that people with permanently lowered vitamin B12 levels have an increased long-term risk of dementia or brain atrophy (brain shrinkage).
  • Cardiovascular system: Here vitamin B12 has a protective effect. Through its ability to break down the amino acid homocysteine, which is toxic to the human body, vitamin B12 has a protective effect on the cardiovascular system. Homocysteine can lead to the formation of arteriosclerosis in the body.