|
|
|
Vitamin B12 Deficiency
Vitamin B12 DeficiencyVitamin B12 Deficiency is the cause of several forms of anemia. The treatment for this disease ..... Vitamin B12 Deficiency is the cause of several forms of anemia. The treatment for this disease was first devised by William Murphy who bled dogs to make them anemic and then fed them various substances to see what (if anything) would make them healthy again. He discovered that ingesting large amounts of liver seemed to cure the disease. George Minot and George Whipple then set about to chemically isolate the curative substance and ultimately were able to isolate Vitamin B12 from the liver. For this, all three shared the 1934 Nobel Prize in Medicine.
The usual daily intake in the Western diet is 5–7 µg (FDA Daily Value); the daily requirement is 1–2 µg. B12 is mostly absorbed in the terminal ileum. The production of intrinsic factor in the stomach is vital to absorption of this vitamin. Megaloblastic anemia can result from inadequate intake of Vitamin B12 , inadequate production of intrinsic factor (pernicious anemia), disorders of the terminal ileum resulting in malabsorption, or by competition for available B12 (such as fish tapeworms or bacteria present in blind loop syndrome). Neurological signs of B12 deficiency, which can occur without accompanying hematologic abnormalities, include demyelination and irreversible nerve cell death. Symptoms include numbness or tingling of the extremities and an ataxic gait.
It has recently been appreciated that deficiency can be treated with oral B12 supplements when given in sufficient doses. When given in oral doses ranging from 0.1–100 mg daily, Vitamin B12 can be absorbed in a pathway that does not require an intact ileum or intrinsic factor The Schilling test can determine whether symptoms of Vitamin B12 deficiency are caused by lack of intrinsic factor, though this is being performed less often due to the lack of availability of reagent for the test.
| |
|
