Iron deficiency in adults may be more common than thought, leaving many 'running on fumes'

Nearly 1 in 3 Americans may have an undiagnosed iron deficiency, a problem that can lead to fatigue, brain fog and difficulty concentrating, a new study suggests.

An analysis of data from more than 8,000 adults in the U.S. revealed that 14% had low iron blood levels, a condition known as absolute iron deficiency, while 15% had the right iron levels but their bodies couldn’t use the essential mineral properly, known as functional iron deficiency, according to the report published Tuesday in JAMA Network Open.

Doctors don’t typically screen adults for iron deficiency, which is why the condition has been overlooked in many people.

The researchers weren’t surprised at the results, however. There had been hints in other studies suggesting iron deficiency might be more widespread than doctors assume.

“This is a common yet underappreciated public health problem,” said study co-author Leo Buckley, a clinical pharmacology specialist at Brigham and Women’s Hospital in Boston. “What’s unique about our study is we were looking at regular people who would not otherwise have been screened or tested.”

Hematologist Dr. Andrew Eisenberger, an associate professor of medicine at the Columbia University Vagelos College of Physicians and Surgeons, said that while iron deficiency “is almost never life-threatening, it’s a tremendous quality of life thing.”

“Tens of millions of people in the U.S. are basically running on fumes either because there isn’t enough fuel in the tank or because the tank isn’t connecting to the engine well,” said Eisenberger, who was not involved with the new research. “In our society we are hardwired to be at peak performance. With this tremendous prevalence of iron deficiency, so many people can’t do their best.”

He hopes the study raises awareness among doctors and patients of how common the problem is.

Although doctors frequently screen for anemia — where a person has too few red blood cells due to low levels of iron — in routine blood tests, people can have enough red blood cells but still have an iron deficiency that leads to symptoms.

“This is an incredibly preventable disease,” Eisenberger said. “So many people come to me who have had this problem for years and years and years, but their doctors have missed it, ignored it or just didn’t know what to do about it. People suffer tremendously. It’s one of the most satisfying things to take care of because people’s quality of life markedly improves.”

For the new study, the Brigham and Women’s Hospital researchers examined health information from the National Health and Nutrition Examination Survey collected between 2017 and 2021 from 8,021 adults. The average age of the participants was 48.

None of the participants had a health condition that is typically associated with iron deficiency, such as anemia, kidney disease, heart failure and pregnancy.

Even with the high numbers of people in the study with iron issues, Buckley doesn’t believe everyone should be screened. He suggests that doctors focus on people with iron deficiency symptoms, such as fatigue and brain fog, and those at high risk for deficiency, such as pregnant women.

Who is at risk for low iron?

The biggest risk factor for iron deficiency is being female.

Pregnant women are especially at risk. “The average pregnant woman needs 1,000 to 1,500 milligrams of additional iron,” Eisenberger said, adding that many women don’t have their iron levels checked till late in pregnancy. “At that point, there’s not enough time to fix it before the woman delivers and the fetus has spent the entire pregnancy with not enough iron.”

Low iron levels in a pregnant woman have been associated with long-term cognitive impairment in children, small size at birth and early delivery, Eisenberger said.

Postpartum women are also at risk of iron deficiency, said Dr. Johanna Contreras, an advanced heart failure and transplant cardiologist at the Mount Sinai Fuster Heart Hospital in New York City.

Moreover, bleeding during menstruation can leave women and girls iron depleted, especially among those who have heavy periods. That’s because the lost blood takes large amounts of iron with it.

The rates of iron deficiency between men and women are more similar after the age of menopause, experts said.

Both women and men can develop functional iron deficiency if they have an inflammatory condition, such as rheumatoid arthritis, said Dr. Hossein Ardehali, director of the Cardiovascular and Renal Research Institute - Center for Molecular Cardiology at the Northwestern University Feinberg School of Medicine.

Sources of nutritional iron

Certain types of diets, such as vegetarian and vegan, can also leave people short on iron, said Ardehali, who was not involved with the new study.

The best food source of iron is red meat, which contains heme, Ardehali said, adding that it can be hard to get enough iron in a diet without meat.

According to Ardehali, other than meat, good dietary sources of iron include:

Seafood

Shellfish

Beans

Dark green leafy vegetables like spinach

Raisins

Apricots

Iron-fortified foods, such as cereals

Research has yet to prove these kinds of iron deficiency can lead to serious long-term health consequences. There are other possible risks.

“Severe anemia can lead people to pass out and hit their heads, have a stroke, or have a heart attack,” Eisenberger said. “This is exceptionally rare. Usually people are so worn down they come to the ER or their doctor’s office before this happens.”

While not the cause, iron deficiency can be a sign of some serious health problems, such as bleeding in the digestive tract, or even colorectal cancer, Ardehali said.

In general, “functional iron deficiency can be a marker for bad health, such as heart failure,” he added.