Iron is a serious powerhouse. It does so much for your body: It’s an essential mineral that plays a role in metabolism, respiration, brain function, and immune function. Perhaps its most well-known purpose is delivering oxygen to tissues. Iron is also responsible for making a very important molecule called hemoglobin. When oxygen passes through your lungs it’s picked up by hemoglobin and delivered to tissues that need it, such as working muscles. Once it gets to your muscle, it unloads the oxygen to be used and picks up the waste product (carbon dioxide) to return to the lungs and exchange it for oxygen.

Everyone needs iron, but it is especially important for endurance athletes. Training can reduce iron levels because of increased cell turnover and the need to make new red blood cells to deliver oxygen. Moreover, endurance athletes can lose iron in multiple ways: sweating, gastrointestinal bleeding, and hemolysis (aka rupturing of red blood cells). Specifically, endurance athletes are prone to a phenomenon called “footstrike hemolysis,” which occurs when people repeatedly land on their feet with the force of their body weight. The impact causes a small amount of red blood cells to break open within the small blood vessels (called capillaries) in the soles of their feet. Similarly, endurance athletes are prone to “runner’s pseudoanemia,” which is a mild anemia that occurs with regular physical activity. It’s not just running—cycling or swimming can also cause the condition. Finally, iron loss can occur due to circulatory stress from muscle activity. Basically the more you exercise, the more iron you use and the more you need to replace it. Because many runners have such high training volume, they are more susceptible to low iron levels.

Low iron levels then have many consequences, such as feeling fatigued, flat, tired, unable to hit intensity targets, frequent illnesses such as colds or viruses, and poor recovery.

When You Need More Iron (or Less)

In general, most athletes could benefit from more iron, but there are times or conditions when it’s absolutely essential.

  • When training volume and/or intensity increases
  • With regular NSAID use, such as aspirin or ibuprofen
  • If you have gut issues
  • Poor dietary intake
  • Vegan/vegetarian diets need to be particularly conscious of iron intake
  • When training at altitude
  • For women with heavy periods

There are, however, times when you actually require less iron, such as:

  • If blood test show elevated iron levels
  • If you’re post-menopausal
  • People who have medical condition with high iron levels, such as hemochromatosis

The daily iron recommendation for women 18-50 years old is 18 mg/day. Men and post-menopausal women have the same recommendation of 8 mg/day.

How Do You Optimize Iron?

We often think of eating steak to improve our iron status, but there are several other strategies. The most efficient and safest way to increase iron is to eat animal foods rich in heme iron such as oysters, clams, turkey legs, tuna, eggs, shrimp, chicken thighs, or beef. Non-heme sources come from plants and include fortified cereals, beans, tofu, lentils, molasses, spinach, whole grains, and peanut butter. Unfortunately, plant sources have significantly less iron and you only absorb 2-20%, so if you consume non-heme iron, you may need up to 80% more iron.

If you don’t eat foods rich in heme iron, you will likely need to take a supplement. First get a blood test to see what your levels are to determine appropriate dosage and duration. If a supplement is deemed necessary, then take it in the morning and as close to finishing exercise as possible. Avoid taking it with tea, coffee, or calcium (either food-based or supplemental calcium), because they prevent iron absorption. Add a source of acid such as vitamin C from fruit, squeeze of a lemon, or tomatoes to enhance absorption. Women will absorb more iron in the first half of their menstrual cycle (first day of period through ovulation), so if taking a periodic supplement, take it during this time.

You can also use cast iron pots and pans to cook, which can add about 6-8 mg per dish. Dry, non-acidic foods don’t pick up much, so use cast iron for acidic foods like spaghetti sauce and chili.

Make sure you are eating enough calories and carbohydrates to support training, in addition to basic physiological function. If energy availability and carbs are too low, a protein called hepcidin increases and blocks iron absorption in the gut.

When it comes to training, running on soft surfaces such as grass, turf, or a track can reduce the impact and amount of red blood cells that break open with footstrike hemolysis.

Iron is essential for health and performance. By optimizing your levels, you set yourself up for achieving your best.