Iron Deficiency Anemia in Female Athletes
Female athletes of child-bearing age are especially at risk for this particular type of anemia. Nearly half of female athletes may experience anemia. Both the act of engaging in high impact activities and presence of a monthly cycle increase blood cell turnover.
Red blood cells (RBC) found in the blood are responsible for carrying oxygen from the lungs to the exercising muscles and tissues. The part of the RBC that binds and carries the oxygen is a ‘hemoglobin’ molecule with four subunits each with an iron molecule at its center. This iron is needed to move the oxygen.
Athletes need more iron
Compared to the general population athletes lose iron through sweat, skin, urine, the gastrointestinal tract, and menstruation if female. Exercise, particularly high intensity and endurance exercise, increases iron losses by as much as 70% when compared to sedentary populations.
Red blood cells also break down more quickly in those who exercise. Though the mechanism is not fully known as to all the reasons why red blood cell and thus iron is depleted at a quicker rate in athletes, there are various proposed mechanisms such as an increase in the amount of oxidative damage induced by exercise.
Also, the mechanical force of a footstrike during endurance running, for example, can increase the destruction of red blood cells in the feet, leading to a shorter red blood cell life span. It has been cited in textbooks that the average recreational runner reduces red blood cell lifespan from 120 days down to only 90 days. This demands the rate of creation of RBC to be increased to match this if there is to be no deficiency.
Both menstruation and exercise deplete RBC from the body
Female athletes are at even higher risk for iron deficiency as compared to males due to monthly blood loss associated with menstruation. Athletes may also be at risk for iron deficiency due to insufficient dietary iron intake. Remember, the body is not very effective at absorbing dietary iron. Athletes, particularly menstruating female endurance athletes, need to be extremely mindful of iron intake in order to meet their bodies’ demands.
This depletion of blood from both exercise and menstrual cycle means a depletion of blood and RBC’s resulting in a lowered level of iron in the blood and a decreased ability to circulate oxygen throughout the body. Those following a strict vegetarian or vegan diet can be at even higher risk for iron deficiency due to the decreased absorption of non-heme iron found in plants and fortified foods.
Additionally this iron deficiency anemia is involved in the all to common ‘female athlete triad’ shown in the diagram – poor energy status, impaired bone health and compromised reproductive function.
Where do we get iron from?
We get iron entirely from our diet. However, we do find it in our diet in two forms: heme and non-heme iron. Heme iron is found in animal sources and non-heme iron in plant sources. This is important due to the vastly different rates of absorption between these two forms; heme (animal) iron is absorbed twice as well as non-heme (plant) iron.
Heme iron is found in the highest amounts in clams, baby clams, oysters, and organ meats followed by red meat (which is the one most people think os). It is found in smaller amounts in the dark meat of chicken and fish.
An easy shortcut is to think the darker the meat, the more iron it has. If you think about it, we find our body iron in our blood and our more aerobic tissues that rely on a high oxygen and blood supply. This is no different in animals; their ‘dark meat’ or higher iron muscles are the more aerobic muscles (just as with us).
Below is a chicken diagram that shows the different areas of white and dark meat on a chicken.
The same can be done with any animal, and it will actually differ from animal to animal dependent on their activity level and their own diet. For example a free range chicken will have much more dark meat and ‘darker’ meat higher in iron when compared to a chicken who is kept in a very small chicken pin and not able to be as active. This is where the distinction between ‘pastured’ and ‘free range’ can matter a good deal.
Non-heme iron from plant sources can be better absorbed when paired with Vitamin C.
Non-Heme Iron comes from plant sources such as these listed:
- Leafy Greens – Spinach, kale, and collard greens
- Legumes- lentils, beans, black beans, and chickpeas
- Nuts and Seeds- cashews, almonds, sunflower seeds, pumpkin seeds peanuts and walnuts
- Fruits- pomegranate, apricots, raisins, prunes and figs
- Other vegetables – tomatoes, beets, and carrots
Plant sources high in vitamin C are:
- Green Leafy Vegetables – kale, brussels sprouts, broccoli, chard, and mustard spinach
- Citrus fruits – lemon, oranges, grapefruits and limes
- Peppers – chili peppers and bell peppers
It is ideal to mix foods high in non-heme iron with foods high in vitamin C to boost absorption.
For example, you could pair a spinach and greens salad with a lemon vinaigrette or simply squeeze a lime over your next salad to ensure better absorption!
What are the signs of iron deficiency anemia?
Loss of cardiovascular performance
Because iron is necessary for oxygen transport and energy metabolism, both of which are critical for fueling aerobic exercise, often the first indicator in a decrease in cardiovascular performance. This is due to a decrease in the amount of circulating oxygen. In iron deficiency anemia, the body cannot make enough red blood cells due to low iron stores needed to create the RBC’s.
Weakness and general fatigue
Due to lack of oxygen needed for energy metabolism and for proper cognitive function, this lowered state can cause weakness at the site of the muscles and cause the brain to transmit the sense of ‘fatigue’ to assist in conserving oxygen levels in the body.
Increased heart rate and shortness of breath
Since the blood is less oxygenated, the heart needed to pump more blood to get adequate levels of oxygen to the tissues that need it. This results in an increase in heart rate and then the lungs to attempt to work harder pulling the oxygen in.
Headaches and Dizziness
This is due to low oxygen levels in the brain and it’s impact on cognitive function. These are two manifestations of the same low oxygen state in the brain.
This is the most unusual symptom on this list, but it has been well documented that when low in stores of minerals such as iron one can crave clay, ice chips,
How is iron deficiency anemia diagnosed?
The most useful of the typical iron study panel is ferritin, which is a marker of iron stores.
Normal Ferritin – 15-150 ng/mL for females; 15-300 ng/mL for males
Iron deficiency – <15 ng/mL
However, even if a lab printout states the ferritin is ‘normal,’ it may actually be too low depending on the athlete, the type of exercise they perform, and their current physical symptoms.
In the sports nutrition community, there is no clear ferritin goal for athletes. Given that certain athletes may need more than double the iron than less active populations, a reasonable ferritin goal would be at least 30-40 ng/mL, if not higher. If a ferritin is dropping significantly during the course of a training cycle, this can also be indicative of developing iron deficiency and the need to intervene, even if the ferritin is within what is generally considered a normal range. It is also worth mentioning that ferritin levels can quickly increase when the body is under stress so results may be falsely high during periods of active infection or inflammation.
Complete Blood Count
This is useful in distinguishing iron deficiency from poor iron utilization states. A complete blood count (CBC) measures the levels of red blood cell in the body and determines whether or not someone is anemic.
Markers of red blood cells in a CBC are hemoglobin and hematocrit. Of note, iron deficiency is only one of the many causes of anemia.
Complete Blood Count Test
How is iron deficiency anemia treated?
Consultation with a sports dietitian is recommended for athletes with iron deficiency. A sports dietitian can perform a thorough dietary review and make recommendations for ways to increase iron intake.
Increase iron in diet first then consider supplementation
Replenishing iron levels through dietary means is always preferable to taking an iron supplement. For some, iron supplementation through oral means (pill or liquid) may be necessary. Oral iron comes in many formulations that are generally equally effective as long as taken regularly.
After dietary changes have been attempted and failed, iron supplementation can be helpful. A recent study suggests that taking oral iron every other day may actually increase iron absorption. The dose, frequency, and duration of iron supplementation can be guided by a sports dietitian or a physician.
Unfortunately, oral iron can be difficult to tolerate due to side effects. Up to 70% of people taking oral iron report GI side effects such as nausea, vomiting, stomach upset, or constipation. Ways to make oral iron supplements more tolerable include taking them with food (though this may decrease its absorption), taking them every other day, or changing the formulation. For those who cannot tolerate or have not responded to oral iron, intravenous (IV) iron can be given under the guidance of a physician.
Taking iron supplements in the absence of iron deficiency can lead to iron overload, which is very dangerous. There are also certain people that are genetically hardwired to absorb more iron and are at risk of iron overload even in the absence of high iron intake.
Remove Foods that Decrease Iron Absorption
There area many different categories of foods that decrease iron absorption. However, there are two main mechanisms:
- the substance binds iron making it unable to be absorbed
- substance out-competes iron for absorption within the small intestinal tract
Three examples of iron binding foods are milk, coffee, and tea which interfere with iron absorption and should not be consumed along with the iron supplement or a high iron meal.
Categories of Substances that Decrease Iron Absorption
- Calcium Containing Foods: milk, yogurt, cheese, tofu and greens
- Eggs: phosvitin in one egg can reduce absorption of iron in a meal by as much as 28%
- Oxalates: Compounds derived from oxalic acid. These are found in spinach, kale, beets, nuts, chocolate, tea, wheat bran, rhubarb, strawberries and herbs such as oregano, basil, and parsley. The presence of oxalates in spinach explains why the iron in spinach is not absorbed. In fact, it is reported that the iron from spinach that does get absorbed is probably from the minute particles of sand or dirt clinging to the plant rather than the iron contained in the plant.
- Polyphenols: include chlorogenic acid found in cocoa, coffee and some herbs. Phenolic acid found in apples, peppermint and some herbal teas, and tannins found in black teas, coffee, cocoa, spices, walnuts, fruits such as apples, blackberries, raspberries and blueberries all have the ability to inhibit iron absorption. Of the polyphenols, Swedish cocoa and certain teas demonstrate the most powerful iron absorption inhibiting capabilities, in some cases up to 90%. Coffee is high in tannin and chlorogenic acid; one cup of certain types of coffee can inhibit iron absorption by as much as 60%. These foods or substance should not be consumed within two hours prior to and following your main iron-rich meal.
- Phytates: a compound contained in soy protein and fiber. Even low levels of phytate (about 5 percent of the amounts in cereal whole flours) have a strong inhibitory effect on iron bioavailability. Phytate is found in walnuts, almonds, sesame, dried beans, lentils and peas, and cereals and whole grains. Phytate compounds can reduce iron absorption by 50 to 65 percent.
Coffee impairs iron absorption: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6165914/
Tea impairs iron absorption: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5093162/
Milk and high calcium foods impair iron absorption: https://www.cambridge.org/core/journals/nutrition-research-reviews/article/effect-of-calcium-on-iron-absorption/900B25C68177A9DCEF384FBD840CF96F
As a first strategy, increasing iron in the diet is crucial since we can only absorb a small portion of the iron we eat. Iron deficiency in athletes, particularly female endurance athletes, is VERY common.
If iron deficiency is suspected, running a blood test is recommended. If a deficiency is found, working with a sports dietitian is suggested to help the athlete find ways to increase dietary iron intake and absorption to ensure that full performance potential of the athlete is not hindered by iron deficiency.
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