The ABC's of the RDA
Nestled within hemoglobin in red blood cells, iron atoms bind oxygen, and shuttle it from the lungs to cells throughout the body. Many enzymes also use iron to extract energy for cell processes.
According to United Nations statistics, 1.3 billion people throughout the world are iron deficient. That's probably because diets in the developing world tend to contain very little red meat, one of the prime sources of readily absorbable iron (known as heme iron). Though vegetables and legumes (like spinach and lentils) also provide iron, this "non-heme" iron is less absorbable.
Scientists have known for decades that iron deficiency causes fatigue and low productivity. Severe forms of anemia can even lead to cardiac arrest.
What's New at Hopkins:
Over the past decade, Hopkins School of Public Health researcher Rebecca Stoltzfus and others have linked iron deficiency to other problems. In studies in Shanghai and Nepal, Stoltzfus, assistant professor of international health, found that anemia appears to increase a pregnant woman's risk of premature delivery and of having an underweight baby. Even mild anemia in pregnant women (who have the highest iron requirements of any group) appears to be associated with low birthweight, Stoltzfus says.
Researchers have also discovered that iron deficiency impairs cognitive development. Stoltzfus is currently studying the link between anemia and cognitive impairments in schoolchildren in Zanzibar. "Anemia is an enormous problem there," she says, largely because most people are infected with hookworm, which causes blood (and thus, iron) loss.
Scientists have yet to establish the mechanism underlying such impairments, Stoltzfus says. One theory: neurons that use the neurotransmitter dopamine (which needs iron to operate) malfunction.
What We Can Do:
Iron deficiency is less of a problem in industrialized countries such as the U.S., where red meat is readily consumed. Those who get their iron through vegetables and legumes should opt for choices that are high-protein (tofu, lentils), and to consume them with foods rich in vitamin C, both factors that increase iron absorption. (Binding agents that inhibit absorption include complex carbohydrates in cereals and legumes, and tannins in tea and coffee.) Physicians recommend that pregnant women take iron supplements.
In developing nations, however, getting pills to everyone who needs them is not always feasible, so researchers have studied other strategies. In Sri Lanka, Stolzfus consulted on a project to fortify flour with iron. Such efforts have constraints, however, since the most absorbable forms of iron tend to degrade over time, or cause food to take on a metallic taste or turn colors. In the U.S., many foods trumpeted as "iron-fortified" use more reactive, less absorbable forms of iron, and thus are not necessarily effective, Stoltzfus notes. --MH
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