Iron & the Athlete

Iron is more than just a mineral—it’s a key player in athletic performance. From oxygen delivery to muscle recovery, learn why athletes need to prioritize this nutrient, how to recognize low iron levels, and where to find the best sources to keep your training on track.
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Let’s talk iron. While pumping iron is one of many athletic pursuits, it doesn’t go well when your body’s iron stores are tanked. Understanding the reason why we need this critical nutrient and how to get it can benefit your training efforts. 

Iron: what is it?

Iron is a mineral. Your body uses it to make hemoglobin, a protein in red blood cells. Hemoglobin transports oxygen from the lungs to all parts of the body. We also need iron to make myoglobin, which is a protein that carries oxygen to muscles. 

There are different types of iron. Heme iron comes from animal products. Non-heme iron comes from plant foods and is sometimes added to fortified food products (like breakfast cereal). The body absorbs iron from plants better when you eat it with animal proteins, or with foods rich in Vitamin C. 


Good sources of Vitamin C: citrus fruits, strawberries, sweet/bell peppers, tomatoes, broccoli 

Iron in dietary supplements comes in several different forms like sulfate, gluconate, citrate, sulfate. They all have either ‘ferrous’ or ‘ferric’ in the name. Some forms of iron are easier to tolerate than others. 

Iron gluconate is a nice option if vitamins make you sick to your stomach or cause constipation (a very common side effect). 

What if my iron levels are low?

You may not have any obvious symptoms at first. The body stores iron in your muscles, liver, bone marrow, and spleen. Once those levels are low, a condition called iron-deficiency anemia occurs. In this type of anemia, your red blood cells shrink in size and contain less hemoglobin. That means you’re getting less oxygen transported to all the places it needs to be. 

Low oxygen means you feel tired, have less productive workouts, have trouble concentrating, may be short of breath, and are just generally weaker. 

Who’s most at risk for low iron?

Those who menstruate, especially in the earlier years during rapid growth, need to replace what is lost in the menstrual flow. Pregnant people also need more for the developing fetus. People with chronic digestive problems may not absorb enough iron. Then, we come to athletes.

Exercise increases the demand your body has for iron. Depending on the exercise/sport, iron is lost more quickly. Endurance athletes are at higher risk because the repeated impact with the ground causes hemolysis, when blood cells are destroyed. 

Mild inflammation from longer training times can also use up iron: bursts of hepcidin, a hormone your liver makes, bring iron levels down to normal when high. Hepcidin causes your body to absorb less iron in the gut and prevents iron leaching from the cells.  We make more hepcidin with inflammation present, and absorb less iron during that time. 

What does this mean in real life? 

In a nutshell, low iron status leads to:

  • lower endurance
  • decreased concentration 
  • fatigue
  • higher risk for injuries 

In other words, it’s going to be harder to hit that PR.

A 2023 meta-analysis of the scientific data supports this. Improved use of energy and more controlled lactate response were noted in people who supplemented their iron when deficient. Those active at higher altitudes had improved VO2 max when taking an iron supplement during training. One study highlighted the need to up your iron by almost 5 mg per day above the normal recommended amount if you’re a runner at higher altitudes. 

Other studies in the meta-analysis noted we absorb iron better after morning exercise vs in the afternoon or in a rested state. Hepcidin levels tend to be higher in the afternoon. If you work out in the morning, your body is primed to take in iron better. The overall theme?  Getting your iron levels back to normal when low can make a difference in performance.

In a retrospective study, 19.7% of the athletes involved were low in iron. Those with iron deficiency tended to be younger (teenage) and born female. Low iron levels are associated with a lower VO2 peak and lower chance of reaching a VO2 peak of over 50.

How much do I need?

You can find a list of current dietary intake guidelines for iron, for all age groups, here

The Daily Value (DV, or general intake goal) is currently 18 mg daily for adults. Foods with 20% or more of the DV are considered excellent sources. 

Where do I get more iron?

Heme iron: 

  • meat, poultry, seafood

Non-heme iron: 

  • iron-fortified breakfast cereals and breads 
  • navy beans, lentils, kidney beans, peas
  • spinach (Popeye knew what was up)
  • nuts
  • dried fruits (like raisins)

The richest sources of any type of iron per serving:

  • fortified breakfast cereals (18 mg iron, or 100% DV)
  • oysters (8 mg iron per 3 oz, or 44% DV)
  • white/navy beans (8 mg per cup, or 44% DV)
  • beef liver (5 mg per 3 oz, or 28% DV)
  • spinach and lentils (3 mg per cooked ½ cup, or 17% DV)

To sum things up…

Iron is very important for getting oxygen to where it’s needed. The demand for oxygen goes up with physical activity, and being low in iron can impact training and final results. Taking a dietary supplement of iron is helpful, but can cause a problem when iron levels get too high. Before taking a dietary supplement, get some lab work first. Or, just start with pumping up your iron levels with your food choices. Pun intended.

References:

  • Solberg A, Reikvam H. Iron Status and Physical Performance in Athletes. Life (Basel). 2023;13(10):2007. Published 2023 Oct 2. doi:10.3390/life13102007https://pmc.ncbi.nlm.nih.gov/articles/PMC10608302/
  • Keller K, Friedrich O, Treiber J, et al. Iron deficiency in athletes: Prevalence and impact on VO2 peak, Nutrition, Volume 126, 2024, 112516, ISSN 0899-9007, https://doi.org/10.1016/j.nut.2024.112516 .
  • Nemeth E, Ganz T. Hepcidin and Iron in Health and Disease. Annu Rev Med. 2023;74:261-277. doi:10.1146/annurev-med-043021-032816https://pmc.ncbi.nlm.nih.gov/articles/PMC9943683/
  • https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/ Accessed 20 Oct 2024.

Discover more about the author, Annette Snyder, MS, RD, CSOWM by visiting her bio page.


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Annette Snyder
ANNETTE SNYDER

Annette Snyder, MS, RD, CSOWM is a Certified Registered Dietitian at Top Nutrition Coaching working with clients who have a history of chronic dieting and are seeking to make lasting habit changes or repair their relationship with food, as well as those seeking help for gut issues, heart health, diabetes and pre-diabetes, and menopause.