Vitamin B12
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Vitamin B12 is important for the normal formation of red blood cells and for the health of the nerve tissues. Undetected and untreated vitamin B12 deficiency can lead to anemia and permanent nerve and brain damage. 1
Vitamin B12 works with folic acid in many body processes including synthesis of DNA, red blood cells and the insulation sheath (the myelin sheath) that surrounds nerve cells and facilitates the conduction of signals in the nervous system. Severe depletion manifests as pernicious anemia, which was invariably fatal until the discovery of B12 in liver. But long before anemia sets in, other conditions may manifest, most often neurological problems (numbness, pins and needles sensations, a burning feeling in the feet, shaking, muscle fatigue, sleep disorders, memory loss, irrational anger, impaired mental function and Alzheimer’s) or psychological conditions (dementia, depression, psychosis and obsessive-compulsive behavior). 2
Vitamin B12 is an essential water-soluble vitamin that is commonly found in a variety of foods such as fish, shellfish, meat, and dairy products. Vitamin B12 is frequently used in combination with other B vitamins in a vitamin B complex formulation. It helps maintain healthy nerve cells and red blood cells and is also needed to make DNA, the genetic material in all cells. Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream. 3
However, nutritional studies conducted in the 1970s cast doubt on this claim, and it is seldom advanced today. A more recent issue is whether a vegan diet can provide enough vitamin B12, which humans need in tiny amounts (1 to 3 micrograms per day) to produce red blood cells and to maintain proper nerve functioning. 4
Deficiency of vitamin B12 (cobalamin), like folic acid, results in megaloblastic anemia (large, immature red blood cells), due to interference with normal DNA synthesis. Additionally, vitamin B12 maintains the myelin sheath that protects nerve fibres; therefore, an untreated deficiency of the vitamin can result in nerve degeneration and eventually paralysis. 5
Cyanocobalamin, also known as Cobalamin or vitamin B12, is a chemical compound that is needed for nerve cells and red blood cells, and to make DNA. It is a water-soluble organometallic compound with a trivalent cobalt ion bound inside a corrin ring. 6
All volunteers had blood samples drawn for the measurement of cobalamin level as well as the levels of the related metabolites methylmalonic acid (MMA), homocysteine (HCYS) and methylcitric acid (MCTR). Thirty- seven (15.3 per cent) of the 242 participants were deficient in cobalamin (level below 165 pmol/L). Of these 37 only 2 were taking multivitamins. An elevated level of MMA was found in 53 participants of whom 46 (87 per cent) were not taking multivitamins. An elevated level of homocysteine was found in 17 participants of whom 16 were not supplementing. The researchers conclude that oral supplementation with 25 micrograms/day or higher may be sufficient to prevent vitamin B12 deficiency in a large proportion of older people. They caution though that their findings cannot be extrapolated to frail or sick old people who may require larger doses to avoid deficiency. 7
Vitamin B12, also called cobalamin, is important to good health. It helps maintain healthy nerve cells and red blood cells, and is also needed to make DNA, the genetic material in all cells (1-4). Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream. 8
Vitamin B12 deficiency is a cause of megaloblastic anemia. In this type of anemia, red blood cells are larger than normal and the ratio of nucleus size to cell cytoplasm is increased. There are other potential causes of megaloblastic anemia, including folate deficiency or various inborn metabolic disorders. If the cause is B12 deficiency, then treatment with B12 is the standard approach. Patients with anemia should be evaluated by a physician in order to diagnose and address the underlying cause. 9
Methionine synthase (in the cytosol) requires methylcobalamin as cofactor, and methylmalonyl CoA mutase (in mitochondria) requires 5′ deoxyadenosylcobalamin as coenzyme. In bacteria, vitamin B12 participates in several other enzyme reactions. Methionine synthase is also called N-5 methyltetrahydrofolate: homocysteine methyltransferase. It sits at the junction between two important metabolic processes: synthesis of DNA and the methylation reactions via S-adenosylmethionine. If vitamin B12 is lacking, folate is trapped as methyl tetrahydrofolate. The metabolite 5, 10 methylene tetrahydrofolate is not formed, and this is specifically required for conversion of deoxyuridylate to thymidy-late, one of the four essential bases in DNA synthesis. In this situation, cell nuclei cannot divide, and there is megaloblastic change which affects rapidly dividing cells of the bone marrow (making blood cells), the gastrointestinal epithelium and germinal epithelium. Effects include anaemia and increased plasma homocysteine. 10
A lack of vitamin B12 can damage nerve cells and cause problems such as tingling and numbness in hands and feet and problems with walking and balance. A vitamin B12 deficiency can cause changes in taste, smell, and vision. Finally, it can cause mental changes, including memory loss and confusion. 11
Pernicious Anemia - Read about a blood disorder called pernicious anemia caused when the body does not make enough red blood cells due to lack of vitamin B12. Symptoms, diagnosis, treatment, and prevention information is included. 12
A second major function of B12, less clearly understood than the first, involves its participation in the development of nerve cells. A coating which encloses the nerves — called the myelin sheath — forms less successfully whenever B12 is deficient. Although the vitamin plays an indirect role in this process, supplementation of B12 has been shown to be effective in relieving pain and other symptoms in a variety of nervous system disorders. 13
Protein — the component of food required for growth and repair of cells — depends upon B12 for proper cycling through the body. Many of protein’s key components, called amino acids, become unavailable for use in the absence of B12. Since one of the steps in carbohydrate and fat processing requires B12 for its completion, insufficiency of the vitamin can also affect the movement of carbohydrates and fats through the body. 14
Cyanocobalamin works to promote normal growth and development, helps with certain types of nerve damage, and treats pernicious anemia. Vitamin B12 helps in the formation of red blood cells and in the maintenance of the central nervous system. Nerves are surrounded by an insulating fatty sheath comprised of a complex protein called myelin. B12 plays a vital role in the metabolism of fatty acids essential for the maintainence of myelin. Prolonged B12 deficiency can lead to nerve degeneration and irreversible neurological damage. 15
References
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