Iron Deficiency in Athletes: Causes, Symptoms & Prevention

The topic of discussion today is iron deficiency in athletes, and specifically why it’s common in females, the signs and symptoms of it, and tips for preventing it. From the best dietary sources of iron to ways to boost its absorption, this post provides everything you need to know about iron nutrition.

Disclosure: this post contains affiliate links. While a very small percentage may be earned from purchases made, it is not at any cost to you. 

What is Iron?

Iron is a mineral that is crucial for energy metabolism, and its use increases during exercise. It is an essential part of hemoglobin, a protein in our red blood cells, that carries oxygen around the body for use by most cells. Iron is also part of a similar protein called myoglobin. Iron stores oxygen in myoglobin which is in muscle cells that require oxygen for aerobic energy production.

Iron Use During Exercise

During exercise, an increase in your breathing rate is an indication that your muscles’ oxygen usage is up, and that iron is working overtime, binding and releasing it for transport and use. Iron is also involved in a crucial metabolic energy system in the mitochondria of cells (the electron transport chain), which is also highly active during exercise to generate energy for muscles to use.

Because of this overuse during exercise, and the fact that high impact activities can crush small amounts of blood cells, endurance athletes can require as much as two times the iron of a non-athlete. Even those engaging in higher than average physical activity will require more. When you add this to already higher needs for females due to menstrual function, it’s no wonder why iron-deficiency anemia is so common in female athletes. 

Symptoms of Iron Deficiency in Athletes

There are many symptoms of inadequate and deficient iron levels. Anemia, meaning low hemoglobin, is most often due to low iron levels, but there are symptoms and blood labs that can show iron inadequacy before the deficiency level of anemia is reached.

Iron inadequacy can be confirmed by low blood ferritin and transferrin. If these levels are low, it’s a good time to amp up iron intake and work on maximizing absorption. If you don’t have any noticeable symptoms, your doctor may not feel the need to test other measures of iron such as transferrin saturation or bone marrow iron stores. 

However, if your ferritin is low enough, or you’re experiencing symptoms like poor ability to get through workouts, or restless leg syndrome, you may actually have iron deficiency without anemia. Be sure to discuss these symptoms with your healthcare providers! Since the body can’t produce iron on its own, it’s important that you consume enough from dietary sources. If stores continue to be low and intake and absorption are not increased, iron deficiency anemia may result.

Iron deficiency anemia causes:

  • Inadequate oxygen transport
  • physical and mental fatigue
  • difficulty recovering from exercise
  • weakened immune system
  • Impaired cognitive function
  • frequent bruising

Iron Sources and Iron Absorption

plant based iron rich food sources

Being aware of dietary sources of iron as well as ways to boost its absorption is important in preventing iron deficiency in athletes. Iron can be found in two forms — heme and non-heme. Heme iron is found in animal products whereas non-heme iron comes from plant foods. In most cases, heme iron does have a higher absorption rate than non-heme, but there are ways to improve non-heme absorption and boost intake without relying on more animal foods, especially red meat, since you’re often hearing me recommending greater intake of plant proteins!

Heme Iron Sources:

  • Red meats (beef, pork, lamb, etc)
  • Poultry, especially dark meat
  • Shellfish
  • Egg yolks

Non-heme iron is less readily absorbed and obtained from plant sources. The less heme iron you eat, though, the more your body adapts to absorb more non-heme iron. To help with the absorption it’s helpful to pair the plant sources of iron with vitamin C as it can increase absorption by 4-6 times! 

Non-heme Iron Sources

  • Lentils, soybeans tempeh, tofu
  • Bean pasta (black bean, explore cuisine edamame, banza)
  • Hemp seeds, pumpkin seeds, cashews, sunflower seeds
  • Leafy greens, quinoa
  • Molasses, cacao, dried apricots

Simply adding a squeeze of lemon to your water can help a bit, but adding vitamin C rich produce to meals and snacks when eating iron is even better. You can even add some orange slices when you’re enjoying dark chocolate. It’s also important to note that drinking coffee and tea can reduce iron absorption so try to avoid drinking these near an iron rich meal. 

New research also shows that iron absorption is elevated immediately following exercise.

Iron-Rich Recipes

quick easy white bean chili

White Bean Chili

Lentil Tacos

Lentil Walnut Stuffing

Spicy Peanut Tofu Stir Fry

Red Lentil and Pepper Chili

How Much Iron Do I Need?

Below are the recommendations for iron from the NIH. However, these numbers are elevated with higher exercise levels and may vary based on genetics and medical history. If you are consuming a vegan or vegetarian diet, you may need  up to 1.8 times more than the recommended amount. Iron intake needs RDAs

NIH Office of Dietary Supplements Fact Sheet 

Side Effects of Iron Supplements

If you are concerned that you may be low in iron it’s important to have blood work confirm your suspicions. Then, meet with a sports dietitian to learn how you can best work on improving intake and absorption while taking a recommended supplement.

It’s important not to take an iron supplement unless you have blood work showing you are inadequate or deficient, or a doctor has prescribed it to you personally for specific reasons (ex: pregnancy, unusual blood loss or large amounts of blood draws, ultra-endurance racing, etc). Iron is stored in several places, including the liver, and high levels can cause oxidation of tissues where it is stored.

Some supplements can also cause undesirable side effects, especially gastrointestinal pain and constipation. Additionally, chronic iron supplementation may interfere with absorption of other minerals such as calcium, zinc, and copper. 

If you do not have access to a dietitian to work one on one, after confirmation from a physician that an iron supplement is recommended, you can explore my supplement recommendations below, as you work on improving your diet. Once iron levels are restored to normal (confirmed by bloodwork), maintain an iron-rich diet with absorption boosters in mind.

-Thorne Iron or Ferrasorb both utilize ferrous bisglycinate, the form research shows to be best absorbed and easiest on the digestive tract. This Thorne product is NSF certified for sport, which is an important 3rd party certification for those participating in collegiate or professional sports. Thorne has a strong reputation in the sports nutrition world and both relies on and conducts plenty of research to support their formulas.

-NOW foods liquid or pill (get $10 off a $40 order with code KELLYNOW10 – this is not an affiliate code). While NOW’s iron is not currently certified, the company is entertaining having all of their products Informed Choice Certified in the future, and you can read more about why I trust them here. Their pill form is also ferrous bisglycinate and some claim liquid forms to be easier on the digestive tract.

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