Do I Need to Take an Iron Supplement?
Iron levels are undoubtedly an important consideration for any runner. We hear over and over how important iron is to running well, and most of us know at least one runner who has talked about their issues with not getting enough iron.
Last month, we talked to one of the researchers of iron studies, Pam Hinton, who gave great insight into just how much iron we need, and how to determine if you are suffering from low iron.
With the health risks it can pose, and the decrease in performance it can lead to, we thought now is the time to dive even deeper into the research to give you the real information you need to know whether you should consider an iron supplement, and why it could be dangerous if you take it without being checked first.
Hopefully you will leave this post feeling confident in what you need to do, and will get yourself tested to see if an iron supplement could help you run faster.
Why is iron so important to runners?
Your red blood cells, which carry oxygen from your lungs to your muscles, are made up mostly of a protein called hemoglobin. At the core of this protein are four iron atoms which can to bind to oxygen.
When you aren’t getting enough iron in your diet, your body can’t produce enough hemoglobin, so your running performance suffers. This situation is called anemia, and its negative effects on endurance performance are well-documented and noncontroversial.
There is, however, another part of the iron equation which is worth a second look, and that is ferritin levels. Ferritin is an iron storage protein; your body uses it to hold on to iron atoms until they’re needed, whether that’s for making hemoglobin or any of the other proteins in your body that include iron.
If I am iron deficient, does that mean I have anemia?
There is some disagreement in the world of sports medicine over whether low ferritin levels by themselves can impair your performance, and whether runners need more ferritin than the general population.
A substantial number of athletes are iron-deficient without being anemic—i.e. their serum ferritin levels are low, but their hemoglobin levels are still normal. Historically, most doctors and researchers have argued that it’s not possible for performance to be impaired if you are iron deficient but non-anemic (normal hemoglobin).
If your hemoglobin levels are normal, you shouldn’t suffer any negative effects from an inability to get oxygen to your muscles.
How does a low ferritin level affect performance?
New research has questioned that premise. Some (though not all) research has indicated that low ferritin levels have a persistent, performance-inhibiting effect even when hemoglobin levels are normal.
A 2011 study by Diane DellaValle and Jere Haas investigated the relationship between serum ferritin levels and performance in rowers.1 After conducting blood tests on 165 female collegiate rowers, DellaValle and Haas determined that 10% were anemic (low ferritin and low hemoglobin), 30% had low ferritin but normal hemoglobin, and the rest had normal values for both. The threshold for what constituted “low ferritin” was set at 20 ng/mL (or µg/L; these units are identical).
After comparing self-reported best time over 2 km in the past six months, the researchers found that the low ferritin/normal hemoglobin group was 21 seconds slower than the rowers with normal ferritin.
By using a technique called multiple regression analysis, DellaValle and Haas were able to demonstrate that the difference in 2 km time between the groups remained statistically significant even when the boundary defining “low ferritin” was raised to 25 ng/mL. This is more than twice the traditional boundary of 12 ng/mL that is used for the general population.
Will an iron supplement improve performance in non-anemic, low ferritin runners?
A 2007 study by P.S. Hinton and L.M. Sinclair at the University of Missouri followed twenty male and female athletes who had serum ferritin levels lower than 16 ng/mL—somewhat lower than DellaValle and Haas’s threshold.2 The athletes were split into two groups; one got an iron supplement; the other got a placebo. After six weeks of training, individual responses were all over the board, but they did have some interesting findings.
Hinton and Sinclair were able to show that the subjects who increased their ferritin levels the most experienced an increase in their ventilatory threshold (they got more fit), and the people who experienced a decrease in ferritin saw their ventilatory threshold drop (they lost fitness).
Another study by DellaValle and Haas, published in 2014, provides further evidence that iron supplements can boost fitness in people with low ferritin but normal hemoglobin.3 The structure of this study was very similar to Hinton and Sinclair’s: forty female rowers were split into two groups; one received an iron supplement, while the other received a placebo. The rowers underwent a 4 km time trial, trained for six weeks, then completed another 4 km time trial.
Though there was no difference in time trial performance between the two groups, the iron supplement group improved their rowing efficiency more than the placebo group, and had lower lactate levels during the first few minutes of the time trial as well.
Why does low ferritin appear to impair performance slightly even when hemoglobin levels are normal?
Some scientists hypothesize that low ferritin levels can cause a drop in your body’s ability to process lactate, since some of the proteins that are important for lactate metabolism use iron too, but there isn’t any solid evidence on this as of right now.
Regardless, these studies indicate that ferritin levels can play a role in performance, even when hemoglobin levels are normal.
DellaValle and Haas’ work also indicates that endurance athletes should probably shoot for a serum ferritin level of at least 20-25 ng/mL.
What’s the bottom line?
If you’ve been feeling like your performances in workouts and races aren’t quite where they should be, think about getting your serum ferritin checked, and if it’s below 25 ng/mL, talk to your doctor about taking an iron supplement.
[bctt tweet=”If your serum ferritin levels are under 20g/ml, its time to take an iron supplement”]
Can Your Iron Levels be Too High?
Now we know that your ability to run fast times in a race can be inhibited when your ferritin is low, even if your hemoglobin levels are normal.
You might be wondering:
“Well, why doesn’t everyone just take an iron supplement? Better safe than sorry!”
Not so fast. In addition to the problems of iron deficiency, distance runners also need to be aware of iron overload. Though rare, iron overload—more properly referred to as hemochromatosis—can cause serious health problems. Getting overloaded on iron isn’t simply a function of getting too much iron in your diet; typically your body is pretty good at regulating its iron levels automatically.
Hemochromatosis and the risk of long term health damage
When your body’s iron levels are high, your intestines absorb less iron from the foods in your diet, keeping your overall iron stores from getting too high, and the converse happens when iron levels are low.1
However, in people with hemochromatosis, a genetic mutation turns off this self-regulating mechanism, and your body absorbs an abnormally high amount of iron from your diet all the time. This can lead to very high blood ferritin levels, and eventually organ damage.
The genetic mutation associated with hemochromatosis is relatively common as far as genetic disorders go; one scientific paper estimates that as many as one in 100 people of Northern European descent could carry the genes for hemochromatosis.2 The mutation is virtually unknown in non-Europeans.
Historically, doctors recommended genetic screening for hemochromatosis among people of European ancestry, given how common the genetic mutation is. However, more recent research has demonstrated that the proportion of people who actually exhibit symptoms of hemochromatosis is lower—somewhere around 2 to 5 percent of the gene-carrying population, according to a study by Jull Waalen and colleagues at The Scripps Resaerch Institute in California.3
Here’s the deal:
Instead of an expensive and complicated genetic test, Waalen et al. recommend testing ferritin levels to screen patients for hemochromatosis, since one of the hallmark signs of the problem is sky-high ferritin levels. This works out conveniently for runners who are considering whether or not they need to be on an iron supplement too, since you’ll want to get your iron checked regardless.
In a 2004 article, medical doctors Heinz Zoller and Wolfgang Vogel caution that iron supplements should be used only after confirming that an athlete really does have iron-deficiency anemia.2 And of course, the best way to do this is with a complete blood count (to find hemoglobin levels) and a ferritin test.
The laboratory-normal range for ferritin is around 12-300 ng/mL for men and 12-150 ng/mL for women—the exact numbers depend on which reference you consult—but recall that new scientific research has shown that distance runners ought to have a minimum of 25 ng/mL to prevent poor performance.4
Fortunately, it’s hard to miss iron overload—according to Waalen et al., real problems only arise when ferritin levels are over 1000 ng/mL. If this is the case, your doctor will talk with you about how to manage your condition.
Iron supplements can do you a lot of good, but only if you need them. The fastest, cheapest, and easiest way to find out if you should be taking an iron supplement is by getting your serum ferritin levels checked.
If they’re low, or borderline-low, an iron supplement is a good idea. If your ferritin is normal, great! You’re getting enough iron in your diet already and you don’t need to bother with the trouble and expense of taking a supplement. Finally, if your ferritin is abnormally high, make sure you talk to your doctor.
Remember to listen to our podcast episode with one of the researchers of iron studies, Pam Hinton, who shared even more detail on iron supplements, and how to make sure you include enough.
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