VITAMIN B-12(cyano-cobalamin)

Vitamin B12 is found in its free-vitamin form, called cyanocobalamin, and in two active coenzyme forms. Absorption of vitamin B12 requires the presence of intrinsic factor, a protein synthesized by acid-producing cells of the stomach. The vitamin is absorbed in the terminal portion of the small intestine called the ileum. Most of body's supply of vitamin B12 is stored in the liver.

Vitamin B12 is efficiently conserved in the body, since most of it is secreted into bile and reabsorbed. This explains the slow development (about two years) of deficiency in people with reduced intake or absorption. Vitamin B12 is stable when heated and slowly loses its activity when exposed to light, oxygen, and acid or alkaline environments.

Vitamin B12 coenzymes help recycle folate coenzymes involved in the synthesis of DNA and RNA, and in the normal formation of red blood cells. Vitamin B12 prevents degeneration of the myelin sheaths that cover nerves and help maintain normal electrical conductivity through the nerves.

Animals ultimately acquire vitamin B-12 from microorganisms, people eating animal products are unlikely to suffer any deficiency. People in traditional vegetarian cultures probably obtained most of their vitamin B-12 through microbial contamination of food. Small amounts may also be obtained from water through its association with soil micro-organisms, and from bacteria normally living in the mouth. With newer, more hygienic practices, vitamin B-12 deficiency sometimes now occurs in people on a vegetarian diet, especially the infants of vegetarian mothers. It has been suggested that a few plants, like comfrey, might be sources of vitamin B-12, But, in the case of comfrey to eat enough of it to obtain the recommended amount of vitamin U-12 would be to risk toxicity and liver damage.

Vitamin-B12 deficiency results in pernicious anemia, which is caused by a genetic problem in the production of intrinsic factor. When this occurs, folate function is impaired, leading to macrocytic anemia due to interference in normal DNA synthesis. Unlike folate deficiency, the anemia caused by vitamin-B12 deficiency is accompanied by symptoms of nerve degeneration, which if left untreated can result in paralysis and death.

Since vitamin B12 is well conserved in the body, it is difficult to become deficient from dietary factors alone, unless a person is a strict vegan and consumes a diet devoid of eggs and dairy for several years. Deficiency is usually observed when B12 absorption is hampered by disease or surgery to the stomach or ileum, damage to gastric mucosa by alcoholism, or prolonged use of anti-ulcer medications that affect secretion of intrinsic factor. Agerelated decrease in stomach-acid production also reduces absorption of B12 in elderly persons. These groups are advised to consume fortified foods or take a supplemental form of vitamin B12.

Common food sources	Meat, liver, kidney, fish, eggs, milk and milk products, oysters, shellfish, poultry, ready-to-eat fortified breakfast cereals, fermented dairy products (cheese, yogurt, etc). The use of fortified foods and supplements are recommended for adults 51 and over.
Major functions	Aids in building of genetic material; aids in development of normal red blood cells; maintenance of nervous system.
Recommended daily intake	Infants: 0.4 - 0.5 microg Children: 0.9 - 1.2 microg Adolescents: 1.8 microg Men & Women: 2.4 microg Pregnant Women: 2.6 microg Lactating Women: 2.8 microg.
Deficiency symptoms	Pernicious Anemia: macrocytic anemia, nervous system disturbances; paresthesia (tingling and numbness in limbs), difficulty walking, loss of bowel and bladder control, dementia.
Overconsumption symptoms	None Reported.
Stability in foods	Vitamin B-12 is water soluble and can be lost in cooking water. It is not sensitive to heat, light, air or oxygen, but can be destroyed by alkaline conditions.

Vitamin B-12 Food Chart

Egg And Chesse Dishes	Content(milligram per 100 grams)
Egg,boiled	1.7
Egg,fried	1.7
Omelette	1.5
Poached	1.7
Raw	1.7
Scrambled	1.4
Cheese soufflé	1.0

Fish and Seafoods	Content(milligram per 100grams)
Roe, Cod, fried	11
Salmon, canned	4
Sardine, canned	23
Tuna, canned in oil	5
Oysters, raw	15
Lobster, boiled	1
Cod, baked	2
Cod, poached	2
Cod, steamed	3
Fish finger, fried	2

Meat and Meat Products	Content(milligram per 100 grams)
Chicken livers, fried	49
Beef, canned	2
Beef, stewed	2
Beefburger	2
Lamb, brain, boiled	8
Lamb, heart, roast	14
Lamb, kidney, fried	79
Lamb, Liver, fried	81
Pork, chop	1
Pork, Leg roast	1
Sausage, liver	8
Salami slices	1
Rabbit, stewed	6
Pork, grilled	1

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Milk and Milk Products	Content(milligram per 100 grams)
Milk, cow's,cond,skim,sweet	0.5
Dried,skimmed	3
Dried,whole	2
Cheese, Camembert	1.2
Cheddar	1.5
Parmesan	1.5
Cottage	0.5
Edam	1.4
Danish Blue	1.2