Female athletes are at risk of low iron stores, and even iron deficiency anemia. High-intensity and endurance cycling increases the turnover and use of iron stores, which can quickly deplete iron reserves if not replenished properly. In addition to exercise requirements, menstrual-related bleeding increases iron losses. Thus, the requirement for female athletes may be higher than your average “Joe”.
So what does this mean exactly? And how does Iron work?
Iron is an important mineral that acts as a transporter of oxygen in the blood (as hemoglobin) and in the muscles (called myoglobin), and is required for red blood cell production. Additionally, iron creates essential enzyme systems needed to produce energy and DNA, as well as supporting a healthy immune system.
Iron is kept in “pools” in the body, which acts as a reserve and storage to be accessed when the body needs it.
There are 3 main pools-
Pool #1 > Storage iron: typically known as ferritin, and mainly found in the liver, bone marrow, and spleen. You can get your iron stores checked with blood work.
Pool #2 > Transport iron: carried by transferrin (a protein) through plasma and fluids throughout the body to the liver, spleen, and bone marrow. This can also be checked with a clinical blood test.
Pool #3 > Oxygen transport iron: combines with oxygen and is carried in the blood as hemoglobin, and also combines with oxygen in the muscle to create myoglobin.
If these iron reserves get low, aerobic ability (and metabolism) can be impaired by the reduced ability to deliver oxygen to the tissues. This hinders the muscles’ ability to use oxygen for energy production, and cycling endurance power and declines……
Iron declines in stages, much like we proceed up in racing categories…..
Reduced iron in the body comes in many forms, with a range of possible symptoms from extreme fatigue to none felt. The clinical iron-depleted stages progress from one to three:
1) Depleted iron stores – reduced ferritin levels and total iron binding capacity
2) Early functional iron deficiency – reduced transferrin levels
3) Iron deficient anemia (or IDA) – reduced hemoglobin and cellular volume (MCV). When you have your iron levels checked, most often clinicians evaluate your hematocrit (measures how much space red blood cells occupy in your blood) and hemoglobin (measures how much oxygen is able to bind to iron on these protein carrier cells) levels in your blood. When these are low, it is usually an indication of iron deficiency anemia.
True iron deficient anemia is when all three iron storage pools are abnormally low, and usually feels like: fatigue, weakness, breathlessness, and impaired aerobic ability. If you notice, these are the same symptoms typically felt when you have the flu or have over-trained. So be careful not to self-diagnose these as iron deficient anemia! Best to get your iron levels checked and have your nutrition assessed to make sure you actually are anemic. Speaking of nutrition…..
The body cannot make iron itself, so we need to eat iron in our food. It’s important to know that there are two different types of iron found in food. These two types are absorbed differently.
> Heme iron is absorbed the best, averaging about 15-18% absorption from the total iron found in heme iron sources. This type of iron is found in red meats, seafood, and poultry.
Heme Iron Sources
|Liver pate||40g (2Tbsp)||2.0-3.0|
|Fish||100 g cooked||0.4-1.3|
Resource: /Australian Institute of Sport 2007
Non-heme iron is found in plant foods like beans, legumes, nuts, cereals, and fortified sports bars/supplements. This type of iron is limited to being <5% absorbed by our body to use for iron-related functions. Non-heme iron absorption can be increased by combining plant foods with heme-containing foods and/or foods with vitamin C, like bell peppers, broccoli, citrus fruits, and melon
|Breakfast cereal (fortified)||30 g (1cup)||2.5|
|Wholemeal Bread||60 g (2 slices)||1.3|
|Spinach||145 g cooked||4.5|
|Lentils/kidney beans||100 g cooked||2.0|
|Dried Apricots||50 g||1.6|
Resource: Australian Institute of Sport 2007
Beware that some foods reduce the absorption of iron- excessive daily use of tea and coffee and alcohol, moderate to high bran-containing foods, and high calcium foods (sound familiar???? See previous August nutrition post if I’ve lost you…). It doesn’t mean you can’t have these foods- but when possible to get your maximum absorption, separate the times when you eat high-iron foods by at least an hour (during non-travel days this is slightly more convenient).
How much iron is enough?
Your daily recommendations vary based on your age, activity/training level, and overall losses. Unfortunately, there is no set amount for athletes at this time, and it is suggested that female athletes get the upper end of the current recommendations for the population.
Your Daily Iron Recommendations from the National Institutes of Health:
Table 1: Recommended Dietary Allowances (RDAs) for Iron
|Birth to 6 months||0.27mg *||0.27mg*|
*AI = Adequate Intake Reference: http://ods.od.nih.gov/factsheets/Iron-HealthProfessional/#en5
More is not better!
OK, let’s be honest here. There tends to be hype and a belief around iron supplementation (like many other types of supplements) that if you take iron pills- you will get faster and be able to go longer! The truth: MAYBE. People who will notice a difference are those that have low iron stores, experience heavy bleeding (menstrual or other), and are traveling to high elevation. If your iron levels are already great (within the upper end of the normal range clinically), taking an iron supplement can work against you. First, a small number of us have hemochromotsis, which is a condition where iron can accumulate in tissues and cause damage/disease. This condition can be undiagnosed for years…. Second, an excessively high iron intake can cause constipation, abdominal pain, diarrhea, vomiting, and in extreme cases tissue damage. Although an overdose is uncommon, even the mild symptoms worth avoiding!
Once again, I encourage you to get your iron stores routinely checked with your regular doctor visits. Especially if you are vegetarian/vegan, avoid red meats, on a restricted diet to lose weight, avoid fortified foods, and/or travel to high elevation frequently. And, as always, attempt to get your iron from food before resorting to an iron supplement!In Good Health,
Sarah Weber, RD., LD.
PS. Look for upcoming Holiday Nutrition posts to help you stay balanced during those food-centric months…..
> Have you had iron-deficient anemia or experienced an iron overdose? Do you know anyone that takes iron to assist performance? Share your experience with us on Facebook!
> Need some help? Contact a qualified dietitian (like me) to help steer you in the right direction….
National Institutes of Health:
Australian Sports Commission:
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