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vitamin B12

Posted on 10. Nov, 2010 by .

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Vitamin B12 is a water-soluble vitamin. Water-soluble vitamins dissolve in water. After the body uses these vitamins, leftover amounts leave the body through the urine.

Typically, water-soluble vitamins can not be stored by the body. Vitamin B12 is special, because the body can store it for years in the liver.

Vitamin B12, like the other B vitamins, is important for metabolism. It helps in the formation of red blood cells and in the maintenance of the central nervous system

Vitamin B12: A vitamin important for the normal formation of red blood cells and the health of the nerve tissues. Undetected and untreated vitamin B12 deficiency can lead to anemia and permanent nerve and brain damage.

Pernicious anemia is a blood disorder caused by inadequate vitamin B12 in the blood. Patients who have this disorder do not produce the protein substance in the stomach that allows the body to absorb vitamin B12. This substance is called intrinsic factor (IF).

Pernicious anemia is simply treated with injections of vitamin B12. The vitamin B12 has to be administered by injection because people with PA do not have IF (or an effective form of IF) and so cannot absorb vitamin B12 taken by mouth.

Pernicious anemia has also been called Addison’s anemia, addisonian anemia, Biermer’s anemia.

Why does vitamin B12 deficiency cause anaemia?

Red blood cells are made in the bone marrow and circulate in the blood. They only have a life expectancy of about four months.

The body needs iron, vitamin B12 and folic acid (one of the B group of vitamins) to produce more red blood cells. If there is a lack of one or more of these nutrients, anaemia will develop.

Anaemia due to a lack of vitamin B12 is also called pernicious anaemia.

Vitamin B12 is essential for the nervous system, which is why a deficiency can also cause inflammation of the nerves (neuritis) and dementia (mental deterioration).

Elderly people are particularly at risk of vitamin B12 deficiency, although it may also be present in the young women.

What causes this type of anaemia?

* Not eating enough foods that contain vitamin B12. A vegetarian or vegan diet can cause deficiency because vitamin B12 is only found in foods of animal origin, such as meat, fish, eggs and milk.
* Inability of the small intestine to absorb vitamin B12. The stomach produces a substance called intrinsic factor to absorb vitamin B12 from food. In the UK, the most common cause of B12 deficiency is a lack of intrinsic factor.

Patients with Crohn’s disease involving the small intestine (Crohn’s ileitis) or who have undergone small intestine resection may not be able to absorb vitamin B12.

Strict vegetarians who consume no animal products can develop B12 deficiency since there is a lack of B12 in vegetables.

The recommended daily allowances of vitamin B12 in the United States are 2mcg for infants, 3 mcg for children under 4 years old, 6mcg for children over 4 years old and adults, and 8 mcg for pregnant women.

It is recommended for adults to take one multivitamin daily. One multivitamin a day is safe and inexpensive. The multivitamin should contain 400 micrograms of folic acid, approximately 2-3 mg of vitamin B6, 6-9 micrograms of vitamin of B12, and 400 IU of vitamin D. The folic acid and the other B vitamins can help lower homocysteine. The vitamin D is one of the important factors in preventing osteoporosis.

High blood homocysteine levels have been found to be a risk factor for atherosclerosis and heart disease. Most doctors will treat homocysteine levels higher than 9-10umol/liter. A doctor experienced in treating coronary heart disease should supervise the treatment of hyperhomocysteinemia. Treatment involves high doses of the B vitamins (1-5 mg/day of folic acid, 10mg/day of B6, and 0.4 mg/day of B12).

ALL vitamin supplements, with the exception of vitamin B12 supplement, are chemically synthesized. This means that they are produced by combining separate chemical elements in a factory. Vitamin B12 is biosynthesized, which means that it is made by using bacterial enzymes.

Food Sources

Vitamin B12 is found in eggs, meat, poultry, shellfish, milk, and milk products.

Side Effects

Vitamin B12 deficiencies occur when the body is unable to properly use the vitamin. Pernicious anemia can make the body unable to absorb vitamin B12 from the intestinal tract.

Because vitamin B12 comes primarily from animal products, people who follow a strict vegetarian or vegan diet and do not consume eggs or dairy products may require vitamin B12 supplements. (Non-animal sources of vitamin B12 exist but are highly variable in their B12 content. They are considered unreliable sources of the vitamin.)

Those who had surgery on specific parts of the small intestine or stomach are also prone to a deficiency if they do not take B12 supplements.

Low levels of B12 can cause anemia, numbness or tingling in the arms and legs, weakness, and loss of balance.

Recommendations

The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for vitamin B 12:

Infants

* 0 – 6 months: 0.4 micrograms per day (mcg/day)
* 7 – 12 months: 0.5 mcg/day

Children

* 1 – 3 years: 0.9 mcg/day
* 4 – 8 years: 1.2 mcg/day
* 9 – 13 years: 1.8 mcg/day

Adolescents and Adults

* Males and females age 14 and older: 2.4 mcg/day

references and thank you
http://www.medterms.com/script/main/art.asp?articlekey=12865
http://www.netdoctor.co.uk/diseases/facts/anaemiab12.htm
http://www.nlm.nih.gov/medlineplus/ency/article/002403.htm

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