When it comes to performance, there’s no doubt that nutrition plays a significant role. In the past, I’ve really focused on acute nutrition: what you can do directly before or during your run to be faster (i.e. here).
An area I have neglected to focus on is what you should be doing from a nutritional standpoint on an on-going basis to stay healthy and perform at your best. One key area that I see as a recurring problem in my practice and athletes around me is iron deficiency anemia.
Iron has a number of roles in the human body. The most important function is how it is incorporated into hemoglobin and myglobin to facilitate oxygen transportation. If these proteins decline, our ability to transport oxygen to our working muscles also drops, and performance plummets along with it (such as here and here).
How do you know if you are anemic?
If you have the general symptoms of anemia (fatigue, weakness, pale skin, dizziness, shortness of breath), and you have some of the risk factors (discussed below), getting some blood work is the way to go!
Sports Anemia vs. Iron Deficiency Anemia
Sometimes, as athletes, we get false positive readings and wrongly are prescribed iron supplementation. This is due to a phenomenon we refer to as sports anemia. In this case, our bodies adapt to the training we go through (especially in the heat), and an increase in plasma volume (fluid content of our blood) is triggered. This is a beneficial adaptation as it increases our ability to transport blood and therefore oxygen while we compete, as I have written about here.
However, in the case of sports anemia, despite the athlete being healthy the blood work will come back with the concentration of red blood cells being lower. The key difference between this and iron deficiency anemia is that the red blood cells do not appear less red or smaller, and their variability in size is not abnormal (which they will be in true iron deficiency anemia).
How much should you take?
So it’s clear; maintaining a heathy iron status is important for running at your best. The recommended daily intake is variable depending on a number of factors. For instance, pre-menopoausal women should intake 18mg/day, while the average man is ok with 8mg/day.
Another important note: there is no evidence supporting that iron supplementation enhances performance in athletes who are not anemic and there are risks if you do supplement when not deficient. So, stick to dietary sources if you are not anemic!
Sources of Iron:
If you are anemic, it’s important to see you doctor to help manage the condition. An iron supplement in combination with a few other supplements (such as B12, Vit C) may be prescribed. The best supplements that are that are the most bioavailable with ingestion are iron sulfate, gluconate and fumarate. Here is a great review for athletes.
If you are NOT anaemic, getting your 8-18mg/day from dietary sources is the way to go. Here are a few common examples. Click HERE to see more.
Selected Food Sources of Heme Iron
|Chicken liver, pan-fried, 3 ounces||11.0||61|
|Oysters, canned, 3 ounces||5.7||32|
|Beef liver, pan-fried, 3 ounces||5.2||29|
|Beef, chuck, blade roast, lean only, braised, 3 ounces||3.1||17|
|Turkey, dark meat, roasted, 3 ounces||2.0||11|
|Beef, ground, 85% lean, patty, broiled, 3 ounces||2.2||12|
|Beef, top sirloin, steak, lean only, broiled, 3 ounces||1.6||9|
|Tuna, light, canned in water, 3 ounces||1.3||7|
|Turkey, light meat, roasted, 3 ounces||1.1||6|
|Chicken, dark meat, meat only, roasted, 3 ounces||1.1||6|
|Chicken, light meat, meat only, roasted, 3 ounces||0.9||5|
Selected Food Sources of Nonheme Iron
|Ready-to-eat cereal, 100% iron fortified, ¾ cup||18.0||100|
|Oatmeal, instant, fortified, prepared with water, 1 packet||11.0||61|
|Soybeans, mature, boiled, 1 cup||8.8||48|
|Lentils, boiled, 1 cup||6.6||37|
|Beans, kidney, mature, boiled, 1 cup||5.2||29|
|Beans, lima, large, mature, boiled, 1 cup||4.5||25|
|Ready-to-eat cereal, 25% iron fortified, ¾ cup||4.5||25|
|Blackeye peas, (cowpeas), mature, boiled, 1 cup||4.3||24|
|Beans, navy, mature, boiled, 1 cup||4.3||24|
|Beans, black, mature, boiled, 1 cup||3.6||20|
|Beans, pinto, mature, boiled, 1 cup||3.6||21|
|Tofu, raw, firm, ½ cup||3.4||19|
|Spinach, fresh, boiled, drained, ½ cup||3.2||18|
The source of the iron also makes a huge difference. It’s been shown that bioavailability (the amount of iron that enters the blood to actually be used) is about 10% in plant-based sources compared to 18% from animal sources. Being a vegetarian and ingesting enough iron is possible, but not easy!
As runners, we face additional challenges. Hard training, without a doubt, puts us at a higher risk for anemia!
Why does this happen? First of all, the physical impact stress of running may cause increase hemolysis (rupturing of red blood cells). There is also the ever-dreaded increase in intestinal bleeding which leads to more blood loss compared to our non-running friends.
There is also a NEW BODY of evidence showing that inflammation induced from running may have a detrimental impact on our iron status by triggering an increased production of the hormone hepcidin. This hormone causes a decrease in iron absorption and an increase in iron excretion.
Hopefully this review helps you to take a look at your specific athlete profile, leading to habits that will help you to maintain your iron status and, as a result, run at your best. If you are not anaemic, maintain a well balanced diet rich in iron sources that satisfy your specific needs based on the factors discussed above.
Also, keep in mind that the quantity of iron in your vegetarian sources are absorbed and utilized ~ 45% less than that found in animal sources- keep this in mind when doing your iron math!
Finally, if you find yourself feeling weak, tired, pale and slow for no clear reason, it never hurts to get some blood work done to see if supplementation is needed. Here is a good general summary if you want more information.