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Vitamin B12 (cyanocobalamin)

Vitamin B12 is an important cofactor in the metabolism of carbohydrates, lipids, amino acids and nucleic acids. The term vitamin B12 is used to describe compounds of the cobalt corrinoid family, in particular those of the cobalamin group. There are four main forms of vitamin B12: cyanocobalamin: hydroxocobalamin, methylcobalamin and adenosylcobalamin. Methylcobalamin and adenosylcobalamin are unstable and damaged by light. They are therefore unsuitable for use in dietary supplements or pharmaceuticals and are not essential since they can be formed from cyanocobalamin or hydroxocobalamin within the body. The main form of vitamin B12 found in food is hydroxocobalamin. The main form used therapeutically and in nutritional supplements is cyanocobalamin, chosen because it is the most stable form and therefore easiest to synthesize and formulate. Cyanocobalamin is the most widely sold analogue of Vitamin B12, with other similar molecules also available. Cyanocobalamin is found in injectable and oral modes of delivery, and has the advantage over other types of B.sub.12 of having a stable shelf life at standard temperature and pressure (STP). Vitamin 12 or cobalamin is an essential vitamin which is present in body fluids such as whole blood, plasma, serum in low concentrations and which has a remarkably strong binding to the B12 transport proteins (the transcobalamins). Among its other functions, Vitamin B-12 is required for the formation of red blood cells and increases tissue deposition of Vitamin A by improving either carotene absorption or its conversion to Vitamin A. Vitamin B12 is also closely related to the actions of four amino acids, pantothenic acid, and Vitamin C, and plays a part in reproduction and lactation. Vitamin B-12 helps reduce the possibility of skin bruises and has been suggested as helpful in combatting alcoholism, diabetes mellitus, osteoarthritis, multiple sclerosis, certain mental diseases, and a number of other diseases and abnormalities. Vitamin B12 compounds have been known to be involved in metabolic processes; and deficiency of vitamin B12 has been known to provoke pernicious anemia and neurological disorders. It is a co-factor essential in the metabolic pathway leading to synthesis of DNA, cell division, as well as cellular metabolism. Biochemical evidence suggests that vitamin B12 compounds may up-regulate gene transcription and thereby protein synthesis. It has been also suggested that vitamin B12 compounds play an important role in immune system regulation. Deficiencies in Vitamin B12 can lead to the inhibition of normal cell division and abnormal maturation and functioning of cells produced. These changes are most apparent in cells that undergo rapid mitosis (cell division), but all dividing cells are affected to some degree. Vitamin B12 deficiency which can be caused by an inadequate vitamin intake via the food, by malabsorption syndrome, by a genetically induced deficiency of one or several transcobalamins or by the presence of gut parasites, can manifest itself in different symptoms which depend on the age of the individual and on the duration of the vitamin B12 insufficiency. Vitamin B12 deficiency is more commonly caused by defective gastrointestinal absorption than from a deficient diet. Therefore, additional factors which can lead to vitamin B12 malabsorption include the combination of gastric achlorhydria and decreased secretion of IF secondary to gastric atrophy or surgery, intestinal parasites, bacterial gastroenteritis and intestinal malignancies. Other disorders which may account for a vitamin B12 deficiency include dietary deprivation (veganism), drugs, organ disease (liver), hyperthyroidism and transcobalamin II aberrations. Because deficiencies of vitamin B12 are generally caused by the inability of the vitamin to be absorbed in the small intestine due to a breakdown in the vitamin B12-intrinsic factor complex transport mechanism, vitamin B12 must therefore be administered systemically.

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