Iron deficiency may affect more than 1 in 6 adults in the U.S., according to research published Tuesday.
Researchers found that 14 percent of Americans may have absolute iron deficiency—defined as a serious reduction or absence of the body's iron stores—and 15 percent may have functional iron deficiency, where the body has enough iron stores but struggles to use it.
Iron deficiency is strongly associated with the condition anemia, defined as low hemoglobin and decreased red blood cells. Anemia can lead to feelings of tiredness and weakness, shortness of breath, confusion, heart failure, irregular heartbeats and death.
But iron deficiency does not just cause anemia. The scientists in this study found that, even among adults without anemia, heart problems, chronic kidney disease and current pregnancy—all associated with iron deficiency—the prevalence of absolute iron deficiency was 11 percent, and functional was 15 percent.
Iron deficiency can also affect bone and heart muscle, decrease physical capacity, damage brain function and lead to heart failure and death, even without anemia.
So, scientists led by Leo F. Buckley of Brigham and Women's Hospital in Boston set out to identify the risk level of iron deficiency among the U.S. general population. The team used data from more than 8,000 adults involved in the National Health and Nutritional Examination Survey (NHANES) from 2017 to 2020.
Women between the ages of 18 to 50 were the group found most likely to be affected by iron deficiency: 34 percent had absolute and 19 percent functional iron deficiency, which the study authors linked to menstruation.
As they got older, the risk of iron deficiency reduced. Between ages 50 and 65, women were 10 percent and 20 percent likely to have absolute and functional iron deficiency, respectively—and the results were almost identical for women over 65: 10 percent and 18 percent.
Among men, the figures were much lower. Just 3 percent and 13 percent of men under 50 were likely to have absolute and functional iron deficiency, respectively. This was 4 percent and 11 percent for 50- to 65-year-olds, and 7 percent and 9 percent for the over-65s.
Overall, functional iron deficiency—where the body struggles to use its iron reserves—was more common than absolute—not enough iron—except in women under 50.
Individuals with anemia, heart failure and chronic kidney disease, or who were pregnant, were more likely to have absolute iron deficiency than functional.
And, the study found, people who were overweight or obese were more likely to have functional iron deficiency, which they said was important because many U.S. adults weigh more than the healthy range.
Buckley's team expected to find other associations between iron deficiency and lifestyle. For example, they initially thought that drinking alcohol, food security and the amount of iron in a person's diet would affect their iron deficiency status.
However, they did not find significant associations between those factors. The authors noted that this might be because they didn't test for factors that might affect how well iron is absorbed by the body.
For instance, when iron-rich foods—such as beef, pork, shrimp, spinach, kale, liver, mackerel and broccoli—are eaten with foods high in vitamin C—such as grapefruit, lime, kiwi, cauliflower, oranges and strawberries—the body is able to absorb more iron than it would if these foods were eaten independently.
The scientists also estimated that, based on their research, doctors may miss up to 70 percent of iron deficiency cases among children and during pregnancy because only very high-risk groups are generally screened for the condition.
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Reference
Tawfik, Y. M. K., Billingsley, H., Bhatt, A. S., Aboelsaad, I., Al-Khezi, O. S., Lutsey, P. L., Buckley, L. F. (2024). Absolute and Functional Iron Deficiency in the US, 2017-2020, JAMA Network Open 7(9). https://doi.org/10.1001/jamanetworkopen.2024.33126
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