In the US, women of childbearing age are more likely to suffer from iron-deficiency anemia than men. Because women lose iron in red blood cells during menstruation, anemia can result if the iron is not replaced. Iron-deficiency anemia can be caused by the following:
- Deficiency of iron in the diet
- An accident or trauma that causes acute blood loss
- Gradual blood loss (bleeding from the intestines or menstruation)
Other than women of childbearing age, children and teens are the next most likely to suffer from iron-deficiency anemia.
This type of anemia is primarily associated with inadequate intake or utilization of vitamin B12 and folic acid—two vitamins necessary for cell division. Thus cells that need rapid replenishment, such as blood cells, are most often affected by a deficiency of these vitamins. The result is that fewer red blood cells are produced and available to carry oxygen to the body's cells, resulting in anemia.
A decreased intake of folic acid from food can result in anemia. Pregnancy, breastfeeding, and periods of rapid growth, which increase the body's need for folic acid, can also contribute to anemia. Heavy alcohol consumption will increase folic acid requirements also.
Vitamin B12 is found in animal products. Thus, vegetarians who consume dairy and egg products are not at increased risk for B12 deficiency, while individuals who are strict vegans (and their breastfed infants) are most at risk for B12 deficiency.
Aging also affects B12 status because less acid is produced in the stomach as we age. Acid helps to release the active form of vitamin B12 in the stomach. From the stomach, B12 travels down the intestines where it is absorbed into the body in the small intestines. Therefore, people who have malabsorption are also at risk for B12 deficiency.
Causes of the megaloblastic anemias include:
- Inadequate intake or absorption of foods with a high B12 content, such as meat, poultry, fish, cheese, milk, and eggs
- Inadequate intake or absorption of foods rich in folic acid, such as green vegetables, whole grains, legumes, leafy greens, broccoli, Brussels sprouts, asparagus, citrus fruits, strawberries, wheat germ, and brewer's yeast
- Low levels of acid in the stomach
- Removal of parts of the stomach or small intestine
- Gluten sensitivity
- Pernicious anemia (see below)
Pernicious anemia is a form of megaloblastic anemia caused by the absence of
intrinsic factor—a chemical substance secreted by cells in the stomach that makes absorption of vitamin B12 possible. Lack of intrinsic factor is thought to be caused by a genetic deficiency or an autoimmune disorder. Vitamin B12 injections are the traditional treatment for pernicious anemia, but the supplement can also be taken orally in large doses.
Pernicious anemia usually affects adults. The symptoms of this disorder come on gradually and may not be immediately recognized. Megaloblastic anemia of any sort must be properly diagnosed and treated because serious problems with muscles and balance may occur if anemia due to vitamin B12 deficiency is treated with folic acid alone.