The term vitamin B12 identifies a group of chemically similar organic substances, containing cobalt and therefore known as cobalamins. The main coenzymatic forms are methylcobalamin, hydroxocobalamin and deoxyadenosylcobalamin.
Cyanocobalamin, a term with which vitamin B12 is commonly identified, is instead scarcely present in the body; however, it represents the more stable form, under which it is marketed in common drugs and food supplements.
For further information: Cobalamine , characterized by alterations of the iron deficiency anemia (from iron deficiency), this disease is due not so much to the mineral deficiency as to the scarcity of erythrocytes. The vitamin B12 complex is in fact essential for the synthesis of red blood cells by the bone marrow. Precisely this primary function is particularly known in the world of sport where cyanocobalamin is part, together with iron and folic acid, in products intended to solve cases of "sports pseudoanemia".
The daily requirement of vitamin B12 is very modest, but still essential. The daily dose required for the adult is about 2 - 2.5 µg, while the deposits present in the organism amount to about 4 mg. The requirement increases slightly during pregnancy and breastfeeding.
, milk and derivatives, beef, eggs); for this reason the risks of deficiency are more concrete in vegetarians. A diet of this type followed by the pregnant mother can be very dangerous for the unborn child.On the other hand, it must be said that B12 is the only water-soluble vitamin of which there are important reserves in the body which, concentrated in the liver, are able to cover its needs for long periods of time (up to three to five years).
Important deficiencies of vitamin B12 are instead common among alcoholics, the elderly and, if it were not for specific drugs, in people who have undergone the removal of the stomach. The gastric mucosa secretes a glycoprotein, called intrinsic factor, which is essential for the absorption of vitamin B12. By binding to it, it gives rise to an indigestible complex that carries it to the small intestine, where it is absorbed after being bound to a specific receptor. In the absence of intrinsic factor, vitamin B12 is almost completely eliminated in the faeces.
Small amounts of B12 are also synthesized by the intestinal bacterial flora, but are not absorbed.
Vitamin B12 contained in algae is considered inactive and competing in bioavailability with the active one. Prolonged use of certain medications, such as antacids in general, can also cause vitamin B12 deficiencies.
