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Causes
By Mayo Clinic staffTo produce adequate numbers of healthy blood cells, especially red blood cells, your body needs a healthy diet that provides a steady supply of vitamins and other nutrients. If your diet is lacking in certain vitamins, vitamin deficiency anemia can develop. Sometimes anemia develops because your body can't properly absorb the nutrients from your diet.
Causes of vitamin deficiency anemias, also known as megaloblastic anemias, include:
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Folate deficiency anemia. Folate, also known as vitamin B-9, is a nutrient found mainly in citrus fruits and leafy green vegetables. A diet consistently lacking in these foods can lead to a deficiency.
An inability to absorb folate from food can also lead to a deficiency. Most nutrients from food are absorbed in your small intestine. People with diseases of the small intestine, such as Crohn's disease or celiac disease, or those who have had a large part of the small intestine surgically removed or bypassed, may have difficulty absorbing folate or its synthetic form, folic acid. Alcohol decreases absorption of folate, so drinking alcohol to excess may lead to a deficiency. Certain prescription drugs, such as some anti-seizure medications, can interfere with absorption of this nutrient.
Pregnant women and women who are breast-feeding have an increased demand for folate, as do people undergoing hemodialysis for kidney disease. Failure to meet this increased demand can result in a deficiency.
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Vitamin B-12 deficiency anemia (pernicious anemia). Rarely, vitamin B-12 deficiency results from a diet lacking in vitamin B-12, which is found mainly in meat, eggs and milk. A shortage occurs because your small intestine can't absorb vitamin B-12. This may be due to surgery to your stomach or small intestine (such as gastric bypass surgery), abnormal bacterial growth in your small intestine, or an intestinal disease, such as Crohn's disease or celiac disease, that interferes with absorption of the vitamin. Vitamin B-12 deficiency can also be caused by a tapeworm ingested from contaminated fish, because the tapeworm saps nutrients from your body. However, a deficiency is most often due to a lack of a substance called intrinsic factor.
Vitamin B-12 is released from food in your stomach. Intrinsic factor is a protein secreted by the stomach that joins vitamin B-12 in the stomach and escorts it through the small intestine to be absorbed by your bloodstream. Without intrinsic factor, vitamin B-12 can't be absorbed and leaves your body as waste. Lack of intrinsic factor may be due to an autoimmune reaction, in which your immune system mistakenly attacks the stomach cells that produce it. Vitamin B-12 deficiency ultimately leads to anemia.
If the deficiency is from a lack of intrinsic factor, it's called pernicious anemia. Pernicious means "deadly." Lack of intrinsic factor was often fatal before the availability of vitamin B-12 shots. Because vitamin B-12 is stored in large amounts in your liver, it may take several years before signs of deficiency appear.
- Vitamin C deficiency anemia. A lack of vitamin C in your diet can also cause anemia. Your body needs vitamin C, found mainly in citrus fruits, to produce healthy blood cells. Vitamin C also helps your body absorb iron, an important building block of red blood cells. Other possible causes of this type of anemia are general malnutrition, cancer, hyperthyroidism or a decrease in the ability to absorb dietary iron.
Certain drugs to treat cancer can also cause vitamin deficiencies.
- Schrier SL. Etiology and clinical manifestations of vitamin B12 and folic acid deficiency. http://www.uptodate.com/home/index.html. Accessed Jan. 19, 2009.
- Pernicious anemia. National Heart, Lung and Blood Institute. http://www.nhlbi.nih.gov/health/dci/Diseases/prnanmia/prnanmia_all.html. Accessed Jan. 27, 2008.
- Folate. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004c.html#sec01-ch004-ch004c-247. Accessed Jan. 28, 2009.
- Vitamin B-12. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004i.html#sec01-ch004-ch004j-379. Accessed Jan. 28, 2009.
- Vitamin C. The Merck Manuals Online Medical Library: The Merck Manual for Healthcare Professionals. http://www.merck.com/mmpe/sec01/ch004/ch004j.html#sec01-ch004-ch004k-403. Accessed Jan. 28, 2009.
- Dietary supplement fact sheet: Vitamin B12. Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/vitaminb12.asp#h3. Accessed Jan. 28, 2009.
- Dietary supplement fact sheet: Folate. Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/folate.asp. Accessed Jan. 28, 2009.
- Food sources of selected nutrients. Dietary Guidelines for Americans 2005. USDA and Department of Health and Human Services. http://www.health.gov/dietaryguidelines/dga2005/document/html/AppendixB.htm. Accessed Jan. 28, 2009.
- Alcoholic beverages. Dietary Guidelines for Americans 2005. USDA and Department of Health and Human Services. http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter9.htm. Accessed Jan. 28, 2009.
