Running can hinder—or encourage—iron absorption. Here’s how to make it work for you.
- Athletes like runners may have an especially difficult time maintaining healthy iron levels because they have higher needs due to greater losses than their sedentary peers—but exercise-related inflammation can interfere with absorption.
- New research finds that timing iron consumption to your workout can affect its absorption levels.
- Iron-deficient runners who consumed iron within 30 minutes of a 90-minute morning run absorbed about 40 percent more than when they consumed iron after an identical run in the afternoon.
If you’re a runner, especially if you’re a woman, there’s a good chance you’ve run low on iron, if not become outright anemic. Iron deficiency is extremely common among endurance athletes like runners, impacting up to 17 percent of male and 50 percent of female endurance athletes, according to past research cited in a new study published in Medicine & Science in Sports & Exercise.
That’s a problem for a load of reasons: Not only does iron makes it possible for red blood cells to carry oxygen to your muscles to power them, but the vital mineral also plays a role in helping you metabolize carbohydrates—your muscles’ primary fuel source during high-intensity activity, like a track workout—and keeping your immune system humming along.
When your iron levels are deficient, your performance—and general health—is compromised.
But iron deficiency in runners can be especially tricky to treat, since exercise-induced inflammation triggers the release of a hormone called hepcidin, which suppresses the absorption of dietary iron. So even if you’re eating more iron or taking a doctor-recommended supplement, you may not be absorbing what you need.
But there may be something you can do to help the process along a bit—and it has to do with timing your iron intake to your workout.
In the Medicine & Science in Sports & Exercise study, 16 endurance-trained runners (10 men and six women) with suboptimal iron levels (serum ferritin levels below 50 μg·L) came in for two exercise sessions. During the first session, they performed a 90-minute treadmill run at 65 percent of their VO2max in the morning, and then consumed a meal and a beverage fortified with 5 milligrams (mg) of iron 30 minutes postrun and 10 hours postrun to simulate an iron-rich breakfast or dinner.
During the second session, which was 14 days later for the men and 28 days later for the women (to account for their menstrual cycle), they performed an identical run in the afternoon. This time, they consumed their meal and iron-fortified drink either 7.5 hours prerun or 30 minutes postrun to simulate eating an iron-rich breakfast or evening meal on the day of an afternoon run.
Researchers found that inflammation and hepcidin levels significantly increased three hours after each running session, though the levels were highest following the afternoon runs, since hepcidin levels naturally rise during the afternoon hours.
They also discovered iron was best absorbed in the morning right after exercise, before hepcidin hit its high point.
In fact, when runners consumed iron within 30 minutes following their 90-minute morning run, they absorbed about 40 percent more of the mineral than when they consumed iron after an afternoon run. The morning runners also absorbed the mineral better than those who took iron in the morning, but ran later in the day.
Because hepcidin levels rise gradually and peak about three to six hours after exercise, the researchers found that there could be a window of improved absorption immediately after exercise before iron absorption is inhibited by hepcidin.
So by timing your iron intake correctly, it could help optimize the amount of iron you absorb and help break the vicious cycle of iron deficiency.
“I would [generally] recommend consuming high iron meals or supplements in the morning,” said study author Rachel McCormick, physiology Ph.D.(c) at Western Australian Institute of Sport. “If you’re running that morning, consume it within 30 to 60 minutes of finishing the run, as this showed the greatest absorption. If the iron is consumed any later after exercise, it’s likely the hepcidin elevation would start kick-in and prevent the iron being absorbed.”
If you have symptoms of iron deficiency, it’s worth having your doctor do a blood test. Vegetarians and women with heavy periods are at greater risk of low iron and anemia.
The primary symptoms of iron deficiency anemia include:
- tiredness and a lack of energy
- shortness of breath
- noticeable heartbeats (heart palpitations)
- pale skin
According to the National Institutes of Health (NIH), most adult men need 8 mg per day; most women (not pregnant or lactating) need 18 mg daily.
Good dietary sources of iron include are red meat, dark poultry (like chicken thighs), beans, nuts, dried fruit, whole grains, fortified breakfast cereals, and most dark-green leafy vegetables, such as kale. You can improve your iron absorption by eating foods rich in vitamin C, like citrus and bell peppers, with a meal. Calcium from dairy foods and tannins (found in tea) can decrease absorption.
