Iron health

Pushing down on the pedals, feeling the muscles in our thighs contract, our hearts beating wildly and our breathing quickening. A wonderful feeling of power as we repeat the exercise tirelessly and the pain melts into the ecstasy of the moment. But that moment can also turn to discouragement when, with burning thighs, we skim the pedals while losing sight of the peloton in the distance. With our legs weakening, we wonder how to regain the vigor that flowed through our veins not so long ago... What if this physical distress were linked to our diet? 

We're starting to get the picture: endurance athletes have different needs than the average sedentary person. They need more calories every day, protein to fuel their muscles, and carbohydrates to keep them going. But beyond these macronutrients, athletes have increased needs for certain essential minerals and vitamins, which play a role in injury prevention, immunity, energy release, and inflammation reduction.

Among other things, iron is of particular concern, especially for active women and vegetarian athletes. 

Iron, what for?

First and foremost, what is iron used for? It is not only found in a famous throne, but also in the body, in the form of two main proteins: hemoglobin (blood cells) and myoglobin (muscle cells). It plays an essential role in cellular respiration by transporting oxygen from the blood vessels to the muscle cells, as well as in the creation and storage of energy.

With such noble functions, it is easy to understand the close link with exercise. The more red blood cells we produce (the effect of exercise), the greater our iron requirements. In addition, we lose iron through sweat or even gastrointestinal bleeding, which is sometimes caused by high-intensity exercise. Note to running enthusiasts: repeated impact on asphalt can increase the rate of hemolysis (destruction of red blood cells).

If you increase your training load or change your eating habits, you may experience some symptoms of iron deficiency, especially if you don't pay particular attention to this element in your diet. The deficiency will result in extreme fatigue, constant lethargy, and a gloomy mood. 

Women and athletes at greater risk

In the general population, women are most affected by iron deficiency, at 3% compared to less than 1% in men. Since they have lower iron reserves and, more importantly, monthly blood loss, it is not surprising that their daily requirement is 18 mg compared to 8 mg for men.

Although the prevalence of impairment is not that high, it is among athletes that the picture is most concerning: reported cases increase to 35% among women and 11% among men (Sim et al., 2019).

This iron deficiency, known as "iron deficiency anemia," may be partly related to insufficient energy intake, a lack of iron reserves, reduced absorption, or even hormonal imbalance. It develops gradually and may take some time before it becomes noticeable in athletes.

In addition, hemoglobin levels can sometimes decrease rapidly when training volume and intensity increase. This is because the increase in red blood cells caused by the training load will temporarily dilute the iron, a condition known as dilution anemia. Although this may seem alarming at first glance, it will resolve naturally. 

What is the connection with vegetarianism?

Iron is bound to proteins that travel in the blood to fill the muscles with oxygen. Thus, the best sources of iron are found in... muscles and blood. Offal (kidneys, liver, heart, etc.) and red meat are therefore the best sources, and their iron is the most easily absorbed. Next come poultry and fish.

Du côté végétal, on trouvera en grande quantité du fer que l’on nomme non héminique, qui sera cependant beaucoup moins bien absorbé (< 5 %). Pourquoi? Parce que des éléments entrent en compétition avec les sites d’absorption privilégiés du fer. Ainsi, certaines protéines, les fibres ou d’autres composés des grains céréaliers empêchent le fer de bien «entrer» dans nos cellules. D’autres éléments comme le calcium, les tannins (thé) ou la caféine (café, chocolat) agissent sensiblement de la même façon en réduisant les opportunités du fer à être absorbé.

This is why vegetarians need 1.8 times more iron than non-vegetarians: 32 mg for women and 14 mg for men. For active vegetarians, it may be beneficial to increase the target values by up to 70% to prevent anemia.

Prevention is better than cure 

A recent intervention study in female athletes showed that a diet rich in iron over a period of 5 months can alter athletic performance. Those who consumed more iron saw an increase in their iron status as well as their VO2 max during a cycling test (Luna et al., 2015).

There are various recommendations that can help you optimize your iron intake, especially if you decide to become vegetarian. Rest assured, a vegetarian or even vegan diet is highly compatible with athletic performance, provided you take precautions to avoid deficiencies.

My first piece of advice: consult a nutritionist if you are changing both your diet and your training volume. In the meantime, here are some key tips to ensure you stay in tip-top shape!

• Vitamin C promotes the absorption of plant-based iron. Add a serving to your vegetarian meals. Example: tomato sauce + pasta. Orange + bread in the morning.

• Increase the variety and quantity of vegetables in your meals.

• Eat fresh or dried fruit as a snack.

• Add baby cereal to your muffin, pancake, or cookie recipes.

• Vary your protein sources (white beans, lentils, tofu, chickpeas).

• Add nuts and seeds to your salads (pumpkin, sunflower, cashew, sesame).

• Add seaweed or herbs to your marinades for tofu or tempeh.

• Try not to drink your coffee at the same time as your meal.

Table: Iron content per 100 g serving of food

REFERENCES

Luna, S., Lung’aho, M., Gahutu, J. B., & Haas, J. (2015). "Effects of an iron-biofortification feeding trial on physical performance of Rwandan women," European Journal of Nutrition & Food Safety, p. 1189-1189. 

Sim, M., Garvican-Lewis, L. A., Cox, G. R., Govus, A., McKay, A. K., Stellingwerff, T., & Peeling, P. (2019). "Iron considerations for the athlete: a narrative review," European Journal of Applied Physiology, pp. 1-16.