Understanding Anemia -- the Basics

What Causes Anemia? continued...

Iron-deficiency anemia occurs because of a lack of the mineral iron in the body. Bone marrow in the center of the bone needs iron to make hemoglobin, the part of the red blood cell that transports oxygen to the body's organs. Without adequate iron, the body cannot produce enough hemoglobin for red blood cells. The result is iron-deficiency anemia. This type of anemia can be caused by:

• An iron-poor diet, especially in infants, children, teens, vegans, and vegetarians
• The metabolic demands of pregnancy and breastfeeding that deplete a woman's iron stores
• Menstruation
• Frequent blood donation
• Endurance training
• Digestive conditions such as Crohn's disease or surgical removal of part of the stomach or small intestine
• Certain drugs, foods, and caffeinated drinks

Vitamin-deficiency anemia may occur when vitamin B12 and folate are deficient. These two vitamins are needed to make red blood cells. Conditions leading to anemia caused by vitamin deficiency include:

• Megaloblastic anemia: Vitamin B12 or folate or both are deficient
• Pernicious anemia: Poor vitamin B12 absorption caused by conditions such as Crohn's disease, an intestinal parasite infection, surgical removal of part of the stomach or intestine, or infection with HIV
• Dietary deficiency: Eating little or no meat may cause a lack of vitamin B12, while overcooking or eating too few vegetables may cause a folate deficiency.
• Other causes of vitamin deficiency: pregnancy, certain medications, alcohol abuse, intestinal diseases such as tropical sprue and celiac disease

During early pregnancy, sufficient folic acid can prevent the fetus from developing neural tube defects such as spina bifida.

Bone marrow and stem cell problems may prevent the body from producing enough red blood cells. Some of the stem cells found in bone marrow develop into red blood cells. If stem cells are too few, defective, or replaced by other cells such as metastatic cancer cells, anemia may result. Anemia resulting from bone marrow or stem cell problems include:

• Aplastic anemia occurs when there's a marked reduction in the number of stem cells or absence of these cells. Aplastic anemia can be inherited, can occur without apparent cause, or can occur when the bone marrow is injured by medications, radiation, chemotherapy, or infection.
• Thalassemia occurs when the red cells can't mature and grow properly. Thalassemia is an inherited condition that typically affects people of Mediterranean, African, Middle Eastern, and Southeast Asian descent. This condition can range in severity from mild to life-threatening; the most severe form is called Cooley's anemia.
• Lead exposure is toxic to the bone marrow, leading to fewer red blood cells. Lead poisoning occurs in adults from work-related exposure and in children who eat paint chips, for example. Improperly glazed pottery can also taint food and liquids with lead.

Anemia associated with other conditions usually occur when there are too few hormones necessary for red blood cell production. Conditions causing this type of anemia include the following:

• Advanced kidney disease
• Hypothyroidism
• Other chronic diseases, such as cancer, infection, lupus, diabetes, and rheumatoid arthritis
• Old age