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Fortified with iron — it’s a phrase many of us may remember reading on the back of cereal boxes. But few of us probably stopped to contemplate why iron, a mineral found in the earth’s crust, was also in our corn flakes.
Iron is an essential mineral that’s necessary for dozens of bodily functions. We need it to survive, yet millions of Americans don’t have enough, especially if they menstruate or consume a primarily plant-based diet.
Moreover, an estimated 5 million Americans have iron-deficiency anemia, a condition defined by an insufficient number of healthy red blood cells. (In some developing countries, more than half the total population has anemia.)
Iron’s most important role is in the creation of those red blood cells. The mineral is a key component of the heme in hemoglobin, a protein that helps transport oxygen from the lungs to the rest of the body. Because the human body doesn’t make iron, it has to absorb it from iron-rich foods or supplements.
Anemia is a serious condition, causing fatigue, weakness, and shortness of breath. Left untreated, iron-deficiency anemia places stress on the heart and may even contribute to heart damage or heart failure.
Even less-than-optimal iron levels can cause a range of troublesome symptoms, so it’s critical to maintain your stores of this vital mineral.
The Low-Iron Risk
Anemia is the result of the body receiving too little iron for too long. “If you’re low on iron, the body will protect red blood cell production first,” says Malcolm Munro, MD, FRCSC, FACOG, a clinical professor of obstetrics and gynecology at the University of California, Los Angeles.
This can have serious consequences for the entire body. “Iron is responsible for [many] enzymatic processes in the body, including those in [the] brain, the repair of DNA, and making liver enzymes,” Munro explains.
And because we can’t survive without oxygen transport, hemoglobin is maintained at the expense of all the other iron-dependent systems.
Prior to full-blown anemia, a host of other symptoms related to iron deficiency may appear: restless legs syndrome, exercise intolerance, brain fog, fatigue. All are good reasons to have your iron levels checked.
Anyone who menstruates is more likely to suffer from both anemia and suboptimal iron levels. And according to the Centers for Disease Control and Prevention, one in five U.S. women experiences especially heavy menstrual cycles, called menorrhagia, which can increase anemia risk. “But it’s been normalized, so much iron deficiency is missed in women,” says Munro.
Recent studies suggest that more than one-third of premenopausal American women may be low in iron. Pregnancy can also increase the body’s demand for iron.
Low iron has a cumulative effect, Munro points out. Heavy periods in adolescence and young adulthood are a setup for anemia during pregnancy, and low iron in pregnancy poses risks to infant health.
“Low maternal iron in pregnancy has been linked to neurodevelopment disorders,” he explains. These include ADHD, autism spectrum disorder, and learning disabilities.
Yet many healthcare practitioners don’t know this. Until she was pregnant herself, functional-medicine practitioner Myrto Ashe, MD, MPH, didn’t think about iron unless patients were anemic. “Suddenly, I felt out of breath going up stairs. I was so tired,” she recalls. Shortness of breath is a sign of low iron; it signals a lack of oxygen in the blood.
After starting an iron supplement, Ashe’s symptoms went away within a week. That’s when she started taking iron seriously.
Measuring Iron Levels
Ashe now tests iron, TIBC (total iron-binding capacity), and ferritin levels in all her patients. An iron test measures iron levels in the blood, while a ferritin test measures the protein that stores iron. Many practitioners, including Ashe and Munro, believe ferritin is a more useful indicator of overall iron levels than hemoglobin alone.
“Hemoglobin can be normal, because hemoglobin will be maintained at the expense of everything else. If ferritin is low, I know stores are low,” Munro says. “If ferritin readings are normal, I can assume hemoglobin is as well.”
Ashe says iron and TIBC levels help illuminate the Goldilocks situation of iron availability:
- Too little iron causes strain on organs and tissues.
- Too much iron can cause oxidative stress.
- Elevated ferritin levels may be caused by excess iron or excess inflammation — or both.
Munro recommends that anyone who menstruates get their ferritin checked regularly to ensure they’re in a good range. Still, the test results can be hard to parse.
Some healthcare providers believe the definition of iron deficiency used by the World Health Organization has thresholds that are too low for ferritin (less than 15 micrograms per liter) and hemoglobin (less than 12 grams per deciliter). Many researchers recommend that the low threshold for ferritin should be between 30 and 50, and hemoglobin should be above 13 to ensure there’s no possibility of anemia.
Both Munro and Ashe note that if you want an iron, TIBC, or ferritin test, you usually have to request it. During pregnancy, a hemoglobin test is typically done at the first prenatal visit in the first trimester, as low iron or anemia can pose a threat to the developing fetus and cause symptoms for the mother.
If you do take iron supplements, it’s still wise to test regularly. While it’s uncommon, too much supplemental iron can cause toxicity. “If you outstrip the carrying capacity of iron in your body, it can cause harm,” Ashe explains. Mild cases mainly lead to gastrointestinal upset, but iron toxicity can also damage the liver and brain.
Ashe has seen patients with too much iron. She recalls one patient who ate a lot of plant-based veggie burgers that contained more heme iron than beef does.
“Their iron was really high, harming their organs,” she recalls.
The Causes of Low Iron
It’s not just menstruation that puts people at risk for iron deficiency. Eating plant-based diets, while good for human and planetary health, can make it harder to get enough iron, largely because we absorb iron more easily from meat than from plants.
In a review of studies on iron depletion that included vegetarians and nonvegetarians, authors found that up to 79 percent of the vegetarian women were deficient in iron; up to 29 percent of the vegetarian men had low levels.
Vegetarians and vegans can maintain healthy iron levels through diet, says Gregory Plotnikoff, MD, MTS, FACP, a functional-medicine practitioner in Minneapolis. “One doesn’t have to have meat to get iron,” he says, though it may require a more conscious effort.
He tests iron levels in most of his patients who eat plant-based diets, especially if they’ve complained about fatigue or restless legs.
Munro says endurance athletes, another health-conscious group, should also check their iron levels. “Sweat is actually a way people lose iron,” he explains, citing studies of distance athletes who became iron deficient during training. One study, for example, found that more than 30 percent of the female runners surveyed prior to and at the 2015 London marathon reported a history of anemia.
Frequent blood donors are another group at increased risk for iron deficiency, with up to 35 percent of repeat donors becoming iron depleted.
Still, the largest group of Americans at risk for iron deficiency — besides those who menstruate — are people taking acid-blocking medications for heartburn, gastroesophageal reflux disease (GERD), or indigestion. These drugs reduce the body’s ability to absorb iron, explains Ashe. (To learn more about how your body absorbs nutrients and how to maximize this process, visit “How Does the Body Absorb Nutrients?“)
Addressing the Source
Correcting low iron levels is typically a two-step process. If your iron stores are low, it’s important to include more iron-rich foods in your diet and start some form of iron supplementation. You’ll also need to work with a practitioner to locate and treat the cause of your low iron.
This may mean addressing heavy menstrual bleeding or discontinuing acid-blocking drugs. In rare cases, low iron levels can be a sign of cancer, so your doctor will also want to rule out blood cancer and the presence of tumors.
Supplements are usually good at restoring iron levels, but they can cause an upset stomach or constipation — though Munro notes that there are simple ways to mitigate these effects. (See “6 Tips for Selecting Safe Supplements” for advice on what to look for when selecting a quality supplement.)
One is to take oral supplements every other day. “With alternate days you absorb at least as much, and maybe more, iron, and you reduce side effects,” says Munro. Ashe also recommends alternate-day dosing for her patients.
[Take] oral supplements every other day. “With alternate days you absorb at least as much, and maybe more, iron, and you reduce side effects,” says Munro. Ashe also recommends alternate-day dosing for her patients.
Plotnikoff counsels his patients who take iron supplements to be mindful of food combinations. Some foods and supplements — coffee, milk, eggs, soy, tea, and turmeric and calcium supplements, for example — can interfere with iron absorption. He recommends taking supplemental iron at least two hours after any other supplements, food, or drink. “It’s really best to absorb iron on an empty stomach,” he says.
If iron loss has progressed to severe anemia, your healthcare provider may recommend intravenous iron. IV supplementation tends to raise iron levels faster than oral supplements, which can take longer to offset symptoms of deficiency.
Top Iron Food Sources and Absorption Tips
If you’re running low on iron, your provider will likely suggest including more iron-rich foods in your diet. Among animal sources, oysters win the prize for best source, with about 8 milligrams (mg) of iron in 3 ounces of oysters. The same amount of steak provides roughly 2 mg of iron.
In general, red meat, poultry, and fish are all excellent sources of heme iron, the type our bodies absorb most easily. We take in up to 35 percent of heme iron, compared with the 2 to 20 percent of nonheme iron we get from plant sources. (There is some nonheme iron in meat as well.)
To further complicate matters for vegetarians, other dietary factors may inhibit nonheme iron absorption. These include the phytic acid found in whole grains and the salutary polyphenols found in tea, coffee, and red wine.
Still, while vegetarians and vegans need to make an extra effort, there are plenty of good plant-based sources of iron. Pumpkin seeds, lentils, blackstrap molasses, quinoa, and beans are all iron rich, as are spinach and dried apricots. One of the best plant-based sources of iron is a cup of white beans, which provides about 8 mg of iron — comparable to oysters (visit “White Beans: Recipes, Techniques, and More.”) Many of these foods are excellent sources of fiber and other phytonutrients as well.
Pairing iron-rich foods with good sources of vitamin C also helps with iron absorption, especially for nonheme sources. This is why doctors have historically recommended iron supplements be paired with orange juice, though that can cause a roller coaster ride for glucose levels.
Plotnikoff suggests patients looking to increase their iron stores try to consume plenty of vitamin C–rich produce, including broccoli, tomatoes, and peppers. Cooking in a cast-iron pan may add bioavailable iron to food too.
Testing Your Iron Levels
So, should you have your iron tested? If you don’t menstruate and do eat meat and seafood, you probably get enough iron from your diet. Guidelines from the National Institutes of Health suggest that a good intake for nonmenstruating adults is 8 mg of iron per day. Anyone who menstruates needs to double that amount, to about 18 mg per day. That number climbs to 27 mg per day during pregnancy.
Meanwhile, if you’re tired, have restless legs, or feel generally run-down, a low-cost iron, TIBC, or ferritin test can help you learn whether low iron levels are at the root of your malaise. If they are, correcting for iron deficiency with food and supplements is a simple enough way to recover your energy. And who doesn’t love a problem that’s easy to solve?
This article originally appeared as “Pumping Iron” in the September/October 2024 issue of Experience Life.
