Iron and the Endurance Athlete…How Important?

I might be dating myself, but when I was growing up we heard about Popeye the Sailor Man cartoon. He loved spinach and after eating spinach his bicep (actually they might have been forearm) muscles would flex and bulge. People equated eating spinach, with getting stronger due to the high iron content. This is partially true. As a non-heme source of iron, spinach is a pretty good source. I’ll explain what a non-heme source is, but first is iron really that vital to endurance athletes?

Yes, iron is actually quite vital to us as athletes, especially those of us in the endurance world. 70% of our body’s iron stores are found in hemoglobin, which moves oxygen from the blood to our cells. 10% of our iron stores are found in myoglobin (in muscles), which moves oxygen into the mitochondria in cells. Iron is also responsible for erythropoiesis (the making of red blood cells), thyroid function, neural function and immune function. So, looking at those key words, oxygen, muscles, red blood cells and proper physiological function, I would say yes, as athletes, we need iron.

Unfortunately there haven’t really been any studies done specifically with athletes and iron deficiency, only the general population put on basic exercise protocols (5x week for 30min). That being said, the general population has about a 3% rate of iron deficiency while some studies would put adolescent females at 10% and males at 1%. Let’s look further:

Who Is Most Susceptible?:

  1. Endurance athletes
  2. Females
  3. Adolescents
  4. Vegetarians or Vegans, even greater if you add in endurance and female
  5. Blood donors
  6. Pregnant women
  7. People with GI disorders (parasites, ulcers), cancer, heart failure
  8. Not in our country (I hope), but developing countries with malnutrition

As a sports nutritionist, I mainly deal with only numbers 1-4, possibly 5 and 6. There are 3 stages of iron depletion and they are categorized by biochemical markers.

Stages of Iron Depletion:

  1. Mild deficiency/depleted iron stores
  2. Marginal deficiency/early functional iron deficiency
  3. Iron deficiency anemia

As you can guess, as you go from 1 to 3, things get worse. Iron depletion is a continual process going from stage 1, to 2 to finally full-blown anemia if measures aren’t taken to correct it. The most reliable marker for iron status is called serum ferritin. It is however susceptible to false positives. So, if you are going to get a blood test, or your child is going to get a blood test, make sure you aren’t sick, you are hydrated, you have not come from exercising and you haven’t had any alcohol before (especially for the children i hope). All of these can elevate your serum ferritin.

How does Iron Deficiency Affect Performance ?:

  • Impaired erythropoiesis (creation of red blood cells) and a drop in hemoglobin
  • Decreased aerobic and endurance capacity (Haas and Brownlie, 2001)
  • Disturbances in brain metabolism, muscle metabolism, immunity and temperature control (Reddy and Clarke, 2004)

One thing that Haas and Brownlie found was that the greater the degree of iron depletion, the greater the improvement in aerobic capacity when supplementing with iron.

Symptoms of Iron Deficiency:

  1. Fatigue
  2. Weakness
  3. Pale Skin
  4. Shortness of breath
  5. Itchiness or Tingling of the Skin
  6. Frequent Infections
  7. Unusual cravings for non food items


Is There a Sports Anemia?

No, there isn’t actually a sports anemia. Scientifically it’s called Dilutional Pseudoanaemia (DP). DP is caused by an increase in your blood volume after exercise, diluting the biomarkers of anemia. With DP, you have low iron status, but your body does not respond to iron supplements. This is vs normal anemia where you have low iron status, but your body does respond to supplements. In this case, doctors need to look at further factors than just bio markers in blood. Is the athlete pale, lethargic, have a compromised immune system, etc.

Causes of Anemia in Athletes?

  • Athletic training, iron loss and iron turnover
  • Diet-inadequate intake and absorbtion-espcially athletes on natural diets who are not eating foods fortified with iron (cereals or breads), vegetarians/vegans and those on fad diets
  • Chronic use of antacids or nsaids
  • Pregnancy
  • Medications
  • Parasites or infections-often seen international athletes

Iron comes in two forms, heme iron and on heme iron. Heme iron comes from animal meat/muscle and is readily absorbed by the body. Non-heme iron comes from plant sources and is not readily absorbed by the body. This is one of the reasons vegetarians/vegans are more susceptible to anemia. But there are ways to increase absorption of iron, and ways we actually inhibit absorption.

How to Increase absorption of Iron, specifically from Non-Heme sources:

  1. Eat a food rich in Vitamin C at the same time-this increases absorption 25%
  2. Eating fermented foods and some organic acids at the same time
  3. There has been a weaker, but still an association with eating foods rich in Vit. A and beta-carotene
  4. Combine a non-heme source with a heme source-this actually increases both absorption rates

What Inhibits Iron absorption:

  1. Phytate or phytic acid-this is found in grains, fruits and vegetables
  2. Tannic acids or flavonoids-tea, coffee, cocoa and red wine
  3. Calcium
  4. Antacids

So now you’re probably confused. If we don’t want to inhibit iron absorption, this would say to not eat healthy things like grains, fruit and veggies. Or drink tea, coffee, red wine or cocoa. That is definitely not the case. If you are in an iron deficient state, or worried about your iron status, eat something rich in vitamin c at the same time. So, for breakfast if you have some bran flakes with fruit, just have an orange or some OJ.

Recommended Amounts of Iron:

RDA for women: 18mg/day, vegetarian women: 33mg/day

RDA for men: 8mg/day, vegetarian men : 14mg/day- men have a higher toxicity rate


Some Good Sources of Iron:


  1. Organ meats-7.5mg
  2. Beef-4mg
  3. Oysters, clams- 4mg
  4. Dark meat turkey- 2.3
  5. Pork-1.5mg
  6. Chicken- 1.2


  1. Fortified oatmeal- 10mg
  2. Lentils- 6.6mg
  3. Kidney beans- 5.2mg
  4. Black beans- 3.6mg
  5. Spinach- 3.2mg
  6. Whole wheat bread- 2mg

So looking at this, it would seem non-heme would be the better choice as they are higher. But remember, non-heme aren’t as easily absorbed.

Can You Take In Too Much Iron?:

Yes, you can take in too much iron. It is rare, from food, but it can occur. It is also more likely in:

  • Using cast iron cookware
  • If you are an alcoholic- not conducive to good athletic performance
  • If you are blood doping- it might be conducive to good athletic performance, but highly illegal
  • A genetic disorder called haemochromatosis
  • Getting iron injections when they aren’t warranted


  1. Eat iron rich foods from both heme and non heme sources every day
  2. Eat foods high in phytic acid (grains, fruits and veggies) with sources of vitamin C
  3. Avoid tea, coffee, cocoa or wine when consuming non-heme foods
  4. If you are on a plant based diet, consuming legumes and foods with vitamin C and vitamin A can help
  5. If you are at risk for iron depletion, ask your doctor for a blood test
  6. Mild depletion of iron stores can reduce your aerobic capacity and endurance
  7. Recovery from iron deficient anemia takes several months-red blood cells turnover every 120 days.







  • By Faith - on

    Thank you for this info Cristina. I was diagnosed and iron deficient anemia when I was pregnant with the twins, 34 years ago. I still take iron supplements everyday and likely will until I hit menopause.

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