Our nutritionist, Benedetta helps explain what iron deficiency is and why female athletes in particular are higher in risk of developing this condition.
What is Iron?
Iron is an essential micronutrient responsible for transporting, storing oxygen in the body and producing energy. 65% of iron is found in the hemoglobin, 10% is bound to myoglobin in muscle tissue and the remainder is found in the liver, bone marrow and macrophages.
There are two forms of iron: heme iron and non-heme iron. Heme iron is contained within the hemoglobin and the myoglobin and is only found in animal sources. Non-heme iron is typically found in plant-based sources and it is less absorbed than heme-iron.
Due to the low absorbability of non-heme iron found in plant proteins, vegan and vegetarians are a risk group for iron deficiency. Moreover, plant proteins such as pulses and legumes contain anti-nutrient factors like phytates and tannins that inhibit iron absorption.
How does our diet affect iron absorption?
Vegan, vegetarian and gluten-free diets have grown in popularity among athletes related to the belief that they confer health and weight management benefits. Several female athletes choose gluten-free diets to improve gastrointestinal symptoms such as bloating, gas, diarrhea and fatigue. Vegetarian diets are also common, as they help to improve health conditions such as hypertension, type-2 diabetes and decrease the risk of chronic disease. These diets are also chosen for environmental and religious reasons.
However, these type of food choices restrict dietary energy and do not meet sport nutrition guidelines for carbohydrates, protein, essential fatty acids and micronutrients particularly iron.
Who would be considered higher risk?
Vegan and vegetarian female athletes participating in endurance sport, are considered to be at a greater risk of compromised iron status not only because they generally absorb less iron than an omnivorous person, but also because they lose iron through the menstrual cycle and through exercise-induced mechanisms associated with endurance activity. It is estimated that women lose 1.6 mg of iron due to the menstrual cycle and that 40% suffer from iron deficiency anemia. For these reasons, iron requirements in women are 14.8 mg, while in males 8.7 mg.
Besides the menstruation, factors that affect iron loss following physical activity include gastrointestinal bleeding, footstrike hemolysis, sweating and iron sequestration in response to inflammation. During an inflammation which is frequent after a physical activity, some proinflammatory molecules called cytokines are released and they activate hepcidin, a peptide hormone that inhibits iron absorption.
Hepcidin is a peptide hormone recently discovered that is secreted in the liver and increases in response to iron overload or inflammation. Since exercise results in an inflammatory response, hepcidin is activated and it blocks iron absorption. Therefore, heavy and frequent exercise training put the athlete at risk of iron deficiency.
In particular, female athletes that participate in aerobic sports such as distance running, or triathlon have the highest risk of iron deficiency compared to those practicing anaerobic sports such as sprinting or swimming. This is attributed to the adaptive responses in muscle tissue which is subjected to a greater need for oxygen in aerobic activities.
What is the female athlete triad?
Iron deficiency can also interact with another prevalent and severe condition in exercising women: “the female athlete triad”. The triad is a syndrome of three interrelated conditions: poor energy status, compromised reproduction function and impaired bone health. The interaction of these conditions can cause severe performance detriments. When this happens, consequences are impaired thyroid function, reduced fuel availability, increased risk of undereating, increased energy expenditure. Other common consequences are hypoxia, impaired fertility and hyperprolactinemia.
The female athlete triad is very common among women, as the majority of them restrict dietary energy (EI; kcal/day) by embracing calorie restrictive diets (vegetarian and gluten-free are very common as mentioned above). This is perceived to achieve a low body weight and confer a competitive advantage. However, the result is poor energy status, compromised reproduction function and impaired bone health (female athlete triad).
What are the dietary treatments to achieve optimal iron status and improve energy status?
Consuming a balanced diet that includes enhancers of iron absorption and iron rich foods is paramount for maintaining the iron status in female athletes.
Foods that contain elevated amount of iron include animal sources like red meat (lamb, beef, pork) and plant-based sources like spinach, broccoli, cabbage, legumes, pulses and sesame seeds. Since these plant-based sources have a decreased absorption rate than meat, it is recommended to consume sources of heme-iron (e.g., red meat) alongside sources of non-heme iron (e.g., vegetables), because heme iron improves non-heme iron absorption.
Moreover, sources of vitamin C such as oranges, kiwi, bell peppers, broccoli are strongly recommended to increase non-heme iron absorption. Fortified products like breakfast cereals and bread should be included in the meal plan of a female athlete. On the other hand, food containing calcium like milk or cheese should be avoided, as calcium is an iron inhibitor. Finally, successful strategies to improve the energy status in women consist of incorporating energy-dense snacks such as protein bars or protein balls and foods rich in nutrients containing carbohydrates, protein and fats like pasta, rice, eggs, peanut butter and walnuts.
This article is written by Benedetta, our nutritionist who specialises in vegan and vegetarian diets and can help you optimise you diets to help you have more energy and feel less run down. To speak with Benedetta, please complete our nutrition assessment form and ask for Benedetta.
References
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