Vitamin B12 (cyanocobalamin, cobalamin)

Vitamin B12 is a water-soluble vitamin that is stored in the liver. Vitamin B12 is a collective term for a group of cobalt-containing compounds known as corrinoids. The principal cobalamins are cyanocobalamin, hydroxocobalamin and the two coenzyme forms of vitamin B12, methylcobalamin and 5-deoxyadenosylcobalamin (adenosylcobalamin). Cyanocobalamin is the principal form of the vitamin used for fortification of foods and in nutritional supplements. Vitamin B12 is also called cobalamin because it contains the metal cobalt.

Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from proteins in foods during digestion. Hydroxocobalamin is a man-made form of vitamin B12. The advantage using hydroxocobalamin is the lack of adverse effects seen with the nitrites such as methemoglobinemia and hypotension. It works by exchanging the hydroxy group for cyanide to form the non-toxic cyanocobalamin (vitamin B12).

Cyanocobalamin is considered the most potent vitamin and is one of the last true vitamins that has been classified. Vitamin B12 combines with a substance called gastric intrinsic factor (IF). This complex can then be absorbed by the intestinal tract. Intrinsic factor is secreted by the stomach lining and it tightly binds vitamin B12 and helps it pass through the intestinal lining and into the blood. Any abnormal production of this intrinsic factor can result in vitamin B12 deficiency. Vitamin B12 is needed for normal nerve cell activity, DNA replication, and production of the mood-affecting substance SAMe (S-adenosyl-L-methionine).

Vitamin B12 also works closely together with vitamin B9 (folate) to regulate the formation of red blood cells and to help iron function better in the body. Vitamin B12 is important for the activity of certain enzymes within calls that control fat, amino acid and carbohydrate metabolism (enzymes are special substances that speed up reactions in the body). Both vitamin B12 and the vitamin folate are essential for the production of genetic material in the body (DNA and RNA).

Vitamin B12 (cyanocobalamin, cobalamin) functions, uses, and health benefits

Vitamin B12's main functions are in the formation of red blood cells and the maintenence of a healthy nervous system. Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells and it aids in the production of DNA and RNA, the body's genetic material. 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.

Vitamin B12 is essential for the proper production of blood platelets and red and white blood cells, the manufacture of vital substances needed for cell function, and the metabolism of nutrients necessary for cell growth. It participates in a variety of cellular reactions to release energy from carbohydrates, fats and protein. Vitamin B12 helps maintain the myelin sheath that insulates nerve fibres from each other. People with vitamin B12 deficiency show irregular destruction of the myelin sheaths, which eventually causes paralysis and death. Vitamin B12 levels decrease with age and various measures of cognitive impairment are associated with reduced B12 status.

The most important use of vitamin B12 is to treat the symptoms of pernicious anemia. Vitamin B9 (folate) and vitamin B12 are critical to the health of the nervous system and to a process that clears homocysteine from the blood. Vitamins B12, B6, and B9 (folate) work closely together to control blood levels of the amino acid homocysteine. Elevated plasma homocysteine concentrations are considered to be a risk factor for vascular disease and birth defects such as neural tube defects.

Vitamin B12 (cyanocobalamin, cobalamin) dosage, intake, recommended daily allowance (RDA)

Most people do not require vitamin B12 supplements. The recommended dietary intake for vitamin B12 is 2 micrograms per day for adults, but women who are pregnant require 3 micrograms per day and who are lactating require 2.5 micrograms per day. Absorption of vitamin B12 is reduced with increasing age. Elderly people may need greater amounts of vitamin B12 than younger people because the body's ability to absorb vitamin B12 from the diet diminishes with age.

Older people have an overgrowth of bacteria in their stomachs. The bacteria that are usually killed by stomach acid compete for the vitamin B12 that is available and take it for their own use. Because vitamin B12 comes primarily from animal products, people who follow a strict vegetarian diet and do not consume eggs or dairy products may require vitamin B12 supplements.

Sources of vitamin B12 (cyanocobalamin, cobalamin)

Vitamin B12 is found naturally in food sources (principally animal products) in protein-bound forms. Animal products are the principal food sources of vitamin B12. B12 cannot be made by plants or by animals. Cyanocobalamin is the principal form of vitamin B12 used in nutritional supplements and for fortification of foods. Methylcobalamin is also available for nutritional supplementation and hydroxocobalamin is available for parenteral administration. Good sources of vitamin B12 include liver, tuna, cottage cheese, yogurt and eggs. Most standard multivitamin supplements also provide the recommended daily allowance of vitamin B12. Food-form B12 is comprised of protein-bound methylcobalamin and adenosylcobalamin. The only reliable unfortified sources of vitamin B12 are meat, dairy products and eggs.

In nature, B12 is solely produced by bacteria found in animals (including humans), so that dirt could actually be considered a natural source of B12. Vitamin B12 is made by bacteria and fungi, but not by yeasts or higher plants. Friendly bacteria reside in large quantities in the gastrointestinal tract of animals and humans. The richest dietary sources of vitamin B12 are liver, especially lamb's liver, and kidneys. Eggs, cheese and some species of fish also supply small amounts, but vegetables and fruits are very poor sources. The richest dietary sources of cobalamin are the liver, brain and kidney. Other sources, include egg yolk, clams, oysters, crabs, sardines, salmon and heart. Lower amounts of cobalamin are found in fish, beef, lamb, pork, chicken, cheese and milk.

Plant foods are generally devoid of B12. Some fermented plant products, e.g., tempeh, may have some vitamin B12. Pseudovitamin B12 refers to B12-like substances which are found in certain organisms, such as Spirulina spp. (blue-green algae, cyanobacteria). However, these substances do not have B12 biological activity for humans. Food-form B12 is comprised of protein-bound methylcobalamin and adenosylcobalamin. The only reliable unfortified sources of vitamin B12 are meat, dairy products and eggs. Another alternative source of vitamin B12 is fortified cereal. Other sources of vitamin B12 are fortified soy milk, vitamin B12 fortified meat analogues (food made from wheat gluten or soybeans to resemble meat, poultry or fish)], and vitamin B12 supplements. There are vitamin supplements which do not contain animal products.

Vegans are recommended to ensure their diet includes foods fortified with vitamin B12. A range of B12 fortified foods are available. These include yeast extracts, Vecon vegetable stock, veggieburger mixes, textured vegetable protein, soya milks, vegetable and sunflower margarines, and breakfast cereals. For the lacto-ovo-vegetarian, reliable sources would include dairy products and eggs which can supply substantial amounts of B12. A slice of vegetarian cheddar cheese (40g) contains 0.5 µg. A boiled egg contains 0.7 µg. Fermentation in the manufacture of yoghurt destroys much of the B12 present.

Boiling milk can also destroy much of the B12. Mushrooms cultivated on manure enriched compost will contain vitamin B12. If the mushrooms are not over washed before use they will contain some B12. There is 0.26ug of vitamin B12 in 100g of mushrooms. A serving of 4-6 mushrooms weighs 75g. Fermented soy products, such as miso and tempeh, shiitake (dried mushrooms) and algae such as spirulina and nori contain practically no vitamin B12.

Vitamin B12 (cyanocobalamin, cobalamin) deficiency

Vitamin B12 deficiency occurs when there is an abnormally low level of vitamin B12 absorbed in the body. The absorption of dietary vitamin B12 occurs in the small intestine and requires a secretion from the stomach known as intrinsic factor. If intrinsic factor is deficient, absorption of vitamin B12 is severely diminished. Vitamin B12 deficiency can be a factor in a variety of different health conditions and disorders. B12 deficiency inhibits of severy decrease the bodies ability to produce blood, increases blood cell destruction, and is very harmful to the nervous system.

Characteristic signs of B12 deficiency include fatigue, weakness, nausea, constipation, flatulence (gas), loss of appetite, and weight loss. Symptoms of severe vitamin B12 deficiency (regardless of the cause) may include burning of the tongue, fatigue, weakness, loss of appetite, intermittent constipation and diarrhea, abdominal pain, weight loss, menstrual symptoms, psychological symptoms, and nervous system problems, such as numbness and tingling in the feet and hands.

Vitamin B12 deficiency is a common problem that affects the general population and the elderly in particular. An abnormally low level of vitamin B12 (cobalamin) is a factor in many disorders. Vitamin B12, also called cobalamin, is important to good health. Vitamin B12 is essential for normal nervous system function and blood cell production. The main sources of vitamin B12 include meat, eggs, and dairy products. For vitamin B12 to be absorbed by the body, it must bind to intrinsic factor, a protein secreted by cells in the stomach.

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.

The result is pernicious anemia (PA). When vitamin B12 is deficient essentially all of the folate becomes trapped as the N5-methylTHF derivative as a result of the loss of functional methionine synthase. This trapping prevents the synthesis of other THF derivatives required for the purine and thymidine nucleotide biosynthesis pathways. Low stomach acid, known as hypochlorhydria, interferes with the absorption of B12 from food but not from supplements. Aging is associated with a decrease in the normal secretion of stomach acid. As a result, some older people with normal levels of intrinsic factor and with no clear cause for malabsorption will become vitamin B12 deficient unless they take at least a few micrograms per day of vitamin B12 from supplements.

Vitamin B12 (cobalamin) plays an important role in DNA synthesis and neurologic function. Persons with the deficiency may be asymptomatic or may have hematologic or neuropsychiatric signs and symptoms. The absorption of dietary vitamin B12 occurs in the small intestine and requires a secretion from the stomach known as intrinsic factor. If intrinsic factor is deficient, absorption of vitamin B12 is severely diminished. Vitamin B12 deficiency may take decades to develop. Most symptoms can occur before the deficiency is severe enough to cause anemia.

Neurological complications also are associated with vitamin B12 deficiency and result from a progressive demyelination of nerve cells. The neurologic symptoms of vitamin B12 deficiency include numbness and tingling of the arms and more commonly the legs, difficulty walking, memory loss, disorientation, and dementia, with or without mood changes. Additional symptoms of B12 deficiency are difficulty in maintaining balance, depression, confusion, poor memory, and soreness of the mouth or tongue. Some of these symptoms can also result from a variety of medical conditions other than vitamin B12 deficiency. It is important to have a physician evaluate these symptoms so that appropriate medical care can be given.

A deficiency of vitamin B12 (cobalamin) deficiency can cause pernicious anemia, which is marked by fewer but larger red blood cells. Deficiencies can cause walking and balance disturbances, a loss of vibration sensation, confusion, and even dementia. Pernicious anemia (PA) is the name of the condition that comes about as a result of severe vitamin B12 deficiency. This condition is usually caused by lack of intrinsic factor in the intestine that is required for the body to properly absorb vitamin B12.

The liver can store up to six years worth of vitamin B12, hence deficiencies in this vitamin are rare. Pernicious anemia is a megaloblastic anemia resulting from vitamin B12 deficiency that develops as a result a lack of intrinsic factor in the stomach leading to malabsorption of the vitamin. The anemia results from impaired DNA synthesis due to a block in purine and thymidine biosynthesis. The block in nucleotide biosynthesis is a consequence of the effect of vitamin B12 on folate metabolism.