Iron, Explained in 90 Seconds

Iron-deficiency anemia affects millions of U.S. adults—especially women.

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Iron-deficiency anemia is one of the most common nutritional problems in the United States. In 2015, almost 3 million doctor visits resulted in a diagnosis of anemia, according to the Centers for Disease Control and Prevention.

There’s a reason iron deficiency is so common, and it has something to do with bioavailability. This refers to how much of the nutrient you absorb that your body can use. To put it simply, just because a meal provides 2 grams of iron doesn’t mean your body is going to get the full 2 grams.

Why Your Body Needs Iron

Iron helps make hemoglobin, a protein in red blood cells. Hemoglobin is the part of the blood cells that transfers oxygen from your lungs to other tissues. Not enough iron means not enough hemoglobin, which means not enough healthy red blood cells, which means not enough oxygen for your body.

This is essentially what iron-deficiency anemia is. You may live with anemia for years without symptoms, but if anemia progresses, you may notice fatigue and weakness. Less commonly, you may experience dizziness, headaches, low body temperature, or brittle nails.

Women are at a higher risk of iron deficiency than men. That’s due to two major factors:

  • Pregnancy: You need more iron to help support the fetus’s development.
  • Menstrual periods: You lose some iron in your menstrual blood. Women with heavier periods are more at risk than women with lighter periods.

Bioavailability + the Types of Iron

There are two main types of dietary iron, and they have different levels of bioavailability.

Heme iron has a slightly higher bioavailability. That means your body is able to use more of it, and less of it goes to waste. Good sources of heme iron include meat (especially organ meat like liver), seafood, and poultry.

Nonheme iron has a lower bioavailability than heme iron. Good sources of nonheme iron include beans, lentils, tofu, potatoes, and nuts, as well as fortified breads and cereals. In fact, those breads and cereals contribute about half of the dietary iron in the average U.S. diet, according to the National Institutes of Health.

You can improve the bioavailability of iron-rich foods by coupling them with foods rich in vitamin C. For example, a meal with iron-rich white beans and vitamin C-rich broccoli means you’ll absorb more iron than if you ate the beans on their own.

Think your fatigue may be caused by anemia? Consult a doctor to see if iron deficiency is holding you back.