Literally translated, the term "anemia" means "without blood." In a clinical setting, anemia is defined as a decrease in the number of red blood cells in your circulation or as an abnormally low content of hemoglobin within those cells. The causes of anemia are legion, but they can be divided into three main areas: blood loss, deficient red blood cell production or excessive red blood cell destruction. Anemia caused by vitamin B-12 deficiency stems from the inadequate production of red blood cells in your bone marrow.
Vitamin B12 Functions
Vitamin B-12, or cobalamin, is a member of the B complex family. According to the Linus Pauling Institute at Oregon State University, B-12 acts as a cofactor for two important enzymes within your cells. As a cofactor for methionine synthase, B-12 participates in the synthesis of DNA and RNA. As part of the L-methylmalonyl-CoA mutase complex, B-12 plays a vital role in the production of hemoglobin, which is the oxygen-carrying protein in your red blood cells. These two activities are essential for allowing your body to manufacture more than 100 million red cells every minute.
B12 Deficiency
Unlike most B vitamins, B-12 is stored in your liver for many months, so the anemia associated with B-12 deficiency is slow to develop, allowing your body to partially adapt to the deficit. Anemia caused by B-12 deficiency, called megaloblastic anemia, is characterized by abnormally large, poorly functioning red cells. Fatigue, loss of appetite, weakness, light-headedness, leg cramps and abdominal pain are common symptoms of anemia. Because B-12 also is needed to keep your nervous system healthy; poor balance, abnormal positional and vibratory sensation, difficulty walking and psychiatric symptoms can accompany anemia.
Treatment
A complete blood count and a vitamin B-12 level usually are used to diagnose B-12 deficiency. According to "The Merck Manual of Diagnosis and Therapy," oral vitamin B-12 treatment with daily doses of 1,000 to 2,000 micrograms is sufficient for treating people whose anemia is not severe or who do not have neurological symptoms. More severe deficiencies require B-12 injections of 1 mg several times weekly until the anemia resolves, which usually takes about six weeks. Thereafter, daily oral therapy or monthly injections can be instituted. If you have neurological symptoms, high-dose injectable therapy might be continued for several months.
Considerations
Vitamin B-12 deficiency is only one cause of anemia. Deficiency of folic acid, another B vitamin, can cause megaloblastic anemia that is indistinguishable from B-12 deficiency. Daily requirements for vitamin B-12 vary from 0.4 micrograms for infants to 2.8 micrograms for lactating females. Daily doses of 500 to 1,000 micrograms, available in many supplements, are safe and frequently used. If you are anemic, ask your doctor about appropriate treatment.
References
- Linus Pauling Institute at Oregon State University: Vitamin B12
- "The Merck Manual of Diagnosis and Therapy, 18th Edition: Vitamin B12 Deficiency"; Mark H. Beers, M.D., Editor-in-Chief; 2006
