Iron Deficiency Among Female Athletes
Iron is an important mineral for the formation of red blood cells, energy production, and brain performance. When it comes to athletic performance iron plays a critical role in energy metabolism, oxygen transport, and acid-base balance. Having an iron deficiency or anemia can be detrimental to athletic performance and overall health. With limited capacity to deliver oxygen to the body, iron-deficient or anemic athletes have a lessened potential maximal oxygen uptake (VO2 max) and work capacity. There is also a greater risk of high blood lactate concentrations during exercise, which can lead to reaching and surpassing the lactate threshold sooner, resulting in muscle fatigue and increased likeliness of pain.
Research suggests that up to 35% of female athletes have an iron deficiency. In fact, female endurance athletes are among the top three groups of individuals at risk for iron deficiency, along with females with heavy periods and vegetarians/vegans. The main reason that athletes are at a higher risk of iron deficiency is that sports increase iron demand while also elevating iron losses. Iron is lost through exercise in several ways including sweating, which leads to iron losses of about 2.5 micrograms per liter of sweat. Other factors such as gastrointestinal bleeding, inflammation resulting in lower iron absorption in the digestive tract, blood in the urine, and the destruction of red blood cells due to forceful ground contact, repeated muscle contraction, vasoconstriction, and metabolic disturbances. For example, endurance athletes frequently experience repeated foot striking, which further exacerbates these effects. Athletes with gastrointestinal diseases may also experience more digestive blood loss due to the induction of intestinal injury, the increased permeability of the gastrointestinal system, and iron malabsorption, which can be heightened by strenuous activity.
Signs of iron deficiency often present as low energy, fatigue, decreased endurance, reduced athletic performance, pale skin, chest pain, fast heartbeat or shortness of breath, headache, dizziness, craving dirt or starch, and brittle nails. It may take months after deficiency begins for symptoms to appear as the body is using iron reserves to remain in optimal balance.
Individuals who eat a balanced diet can normally obtain plenty of iron through diet alone. In fact, most foods contain some amount of iron, even if it is small. Women require about 18 mg of iron a day, while men need about 9mg. Despite having a higher risk of iron loss, official recommendations for female athletes do not exceed the recommended daily allowance of 18 mg per day, and the goal should be to obtain this through dietary intake.
It is important to note that sources of iron can vary. Dietary iron comes in two forms: heme and non-heme iron. Heme iron, derived from animal sources, is more efficiently absorbed by the body (about 15-35%). Sources of heme iron include beef which contains about 2.1 mg of iron per 3 ounces and other meat sources such as chicken, turkey, ham, and veal all of which contain 0.6 mg of iron per 3 ounces serving.
Non-heme iron can be obtained from fortified sources such as cereal (providing 3.4 mg iron per serving), beans and tofu (also 3.4 mg per serving, dried apricots, wheat germ, pumpkin, squash (all with 2.2 mg per serving), and nuts, seeds, raisins, dried peaches and prunes, broccoli, spinach, pasta, bread, and brown or enriched rice (each containing approximately 0.7 mg per serving). In the Western diet, grain products account for the largest portion of non-heme iron intake, making up 50% of the total. Non-heme iron requires alteration and reduction to ferrous iron in the body and is typically less bioavailable compared to heme iron. In fact, only 2-20% of non-heme iron from dietary sources is absorbed by the body. However, some strategies can enhance the absorption of non-heme iron. Pairing iron-rich plant foods with sources high in vitamin C, such as citrus fruits, strawberries, tomatoes, bell peppers, and cruciferous vegetables, helps capture and store non-heme iron in a more readily absorbable form. So, combining these foods can promote iron absorption.
While certain foods enhance iron absorption, others can inhibit it. These inhibitors include dairy products and caffeine. Milk and other sources of calcium have been shown to interfere with the body’s ability to absorb iron from both heme and non-heme sources. Similarly, caffeinated beverages like coffee and tea hinder the absorption of non-heme iron due to the presence of polyphenols which bind to iron and prevent the transport of nutrients into the intestinal cells. It is not necessary to eliminate dairy and caffeine from your diet, however, it is recommended to separate the consumption of iron inhibitors and iron-rich meals by about one to two hours to minimize their inhibitory effects.
Cooking methods can also influence the amount of iron and vitamin C in non-heme iron sources, particularly leafy greens. Cooking breaks down the cell walls of vegetables, releasing more nutrients, however, this can also increase the chance that nutrients are leached out of the vegetable. Grilling or roasting helps to retain the most nutrients from these foods. Quick cooking methods such as steaming and microwaving have minimal effects on iron and vitamin C losses compared to boiling which has the largest effect on nutrients being overly released and lost. Additionally, using a cast iron skillet can easily increase the iron content in meals. Studies have shown that continuous cooking with cast iron cookware can significantly impact hemoglobin and iron indices, potentially reducing the risk of iron deficiency and iron deficiency anemia.
It is suggested that those in high-risk groups, such as female athletes, should have their iron levels checked every three months to every year, depending on the level of risk. For women typical ranges for the labs are as followed:
Serum Iron: 50-170 mcg/dL
Hemoglobin: 12-15.5g/dL
Hematocrit: 35.2-44.9%
TIBC: 240-450 mcg/dL
Transferrin: 20-50%
If you are a female athlete and your doctor is not already monitoring your iron levels, make sure to advocate for yourself! Maintaining the right balance of intake and output regarding an iron-rich diet and exercise-induced blood loss can have a significant impact on your athletic performance.
Iron supplementation may be required for individuals with low iron levels, low iron stores, or anemia, but should only be done after consulting with a medical professional. Iron supplements can reverse iron deficiency when dietary changes alone are unsuccessful, but attempting to obtain enough iron through a balanced diet should be the primary consideration.