Adventures with Iron Deficiency, Part 1

(Super obvious disclaimer: I am not a doctor, nutritionist, dietitian, coach, etc. and have absolutely no formal training whatsoever in medicine, diet, sports training, etc. and probably no one should listen to me about anything. Everything I know, I've learned from reading or talking either to people who ARE experts or other female runners who have had similar experiences. This entire blog is just Some Lady Rambling on the Internet and if you are getting your medical and/or training advice from me something in your life has gone very, very wrong; please go pay an actual expert actual money.)

=====

People didn't talk much about iron levels when I was in high school and college. Or, at least, not my particular circle of runners & coaches. In fact I don't think I ever even had mine tested until I got a summer job running the barn at a Girl Scout horseback riding camp in college, and I had no idea what the numbers meant or even what the deal with low iron really was, except for some vague notion of how iron bonds to oxygen and that's why you need it to make red blood cells. Which, y'know. Sounds important. But wasn't exactly something I worried about.

My next encounter with iron talk was many, many years later, reading running blogs by people way, way, WAY faster than me (like RoseRunner, and Kris Lawrence, and Camille Heron), how they'd started generally feeling shitty on their runs while training hard, and so the doctor said, "You know, let's just check your iron just to be safe." It was't a problem I was personally having at the time, but I guess I must have put a mental pin in it to revisit if it seemed relevant.

So, a few years later, while I was training for the Eugene Marathon, I started feeling just really awful. Like tired and cold all the time even when there was no good reason for it, and so many runs, even short easy ones, where I felt like I might fall over at any moment. The way I tried to describe it to my doctor was that it felt like being sleep deprived and low blood sugar at the same time, only it happened when I was definitely definitely not either of those things. Also my workouts were just a slog. I could hit the times still, usually, but felt like I was dragging myself through them & when I got home I just wanted to lay on the couch and not move.

But of course doctors are funny so he was like, "Sounds like marathon training to me!" Har har har. And this is the frustrating part. Doctors are so used to dealing with sick, broken, sedentary or barely-not-sedentary people, so sometimes you tell them you're running 50-60 miles a week and you're feeling super tired and shitty and they just laugh at you. So you have to try to explain that no, you do this all the time & have trained for plenty of marathons before and you know what it feels like, thankyouverymuch, and you definitely know the difference between week-12-of-the-training-cycle feeling shitty and something-else-is-wrong-here feeling shitty.

So if you're really really lucky, your doctor *might* just humor you and order an iron test and also a few others that seem relevant, and almost guaranteed, the test will come back saying you are absolutely completely 100% just fine in the iron department.

I wasn't 100% convinced, though, so I started doing some reading about endurance athletes and iron, and here is what I found out:

1) There are two different numbers that you have to look at when talking about iron.

The first one, hemoglobin, is the one everyone knows about and what most people mean when they're talking about low iron. Hemoglobin is what they check if they think you might be anemic. "Your body needs iron to make hemoglobin-rich red blood cells, which carry oxygen from your lungs to your muscles. If a blood test shows that the hemoglobin concentration in your blood is lower than normal, that means you're anemic: You may feel weak and tired, and the most common cause is low iron." -Alex Hutchinson in this article. If you just go to the doctor and say "I feel really exhausted and crappy, can you check my iron?," almost guaranteed they're going to do a hematocrit, which measures hemoglobin.

The second one is ferritin. You can think about ferritin as stored iron--the iron in your bone marrow that your body starts dipping into if it's having trouble making enough red blood cells. When you train and get fitter, one reason that happens is because your body actually makes more blood--that's right; endurance athletes actually have more blood in their bodies than normies! Making a bunch more blood means making a bunch more red blood cells to keep the balance right, and if you don't have enough iron coming into your body to keep up, it's going to start dipping into those bone marrow ferritin stores in order to make enough red blood cells.

So:

Low hemoglobin = anemia.

Low ferritin = iron deficiency.

You can have one and not the other. They are NOT the same thing.

"According to research from the Centers for Disease Control and Prevention, between 9 and 11% of teenage and adult women are iron deficient, while only 1% of teenage and adult men are iron deficient. In this context, 'iron deficient' means serum ferritin levels below the standard lab reference ranges for the general population...Iron deficiency anemia (meaning low hemoglobin in addition to low ferritin) occurs in less than half of those who have low ferritin." - John Davis, Running Writings.

2) For years, coaches and endurance athletes--especially female athletes--felt sure there was a relationship between low ferritin and feeling crappy during hard training. These athletes would have both iron tests done and learn that their hemoglobin was fine but their ferritin was in the toilet, and then they'd take iron supplements and feel better.

A lot of doctors, however, absolutely refused to acknowledge the connection. "It's hemoglobin, not ferritin, that carries oxygen to the muscles, so even if low ferritin could cause anemia later, if your hemoglobin levels are normal, how could your performance be suffering?"

But science continued to science on, and as of the 201x's, we now have very some very good explanations for why low ferritin might make runners feel crappy even if their hemoglobin is fine.

First, it turns out that you need iron for all sorts of things, not just making red blood cells. Iron is involved in regulating metabolism, immune function, and certain brain processes, for starters, and some of those things are very likely to affect how good you feel when you're asking a lot of your body.

"The theory, [a scientist] explains, is that your body preferentially uses whatever iron is available to optimize hemoglobin levels, potentially shortchanging iron's other important roles if the supply is limited." -Alex Hutchinson, same article.

"There are several iron-dependent enzymes involved in the transformation of chemical to mechanical energy during oxidative metabolism, which is the main energy pathway used by rowers [and runners] during endurance training and most competitive events performed...around the lactate threshold. During high-intensity activities such as a 2K ergometer time trial [or a running race], impaired O² transport capacity, even in the absence of frank anemia, may result in increased reliance on anaerobic metabolism to produce energy....So, in layman's terms, iron deficiency can impair your production of enzymes important for creating aerobic energy, so you're forced to dig into your anaerobic energy systems earlier, thus becoming fatigued more rapidly." - John Davis, same article

So if you're an endurance athlete, your body is going to fight pretty hard to keep your hemoglobin up; you probably won't see deficiencies there unless things are really, really dire. And in the mean time, all those other pieces--metabolism regulation, immune function, etc.--could be getting short changed and causing you to suck.

3) Women have it worse, and it's not just pro or highly competitive women; A 2010 Swiss study reported that 28% of female marathoners of all levels had iron deficiency, versus only 1.6% of male marathoners. This is probably due partly to menstruation and partly to the fact that women just consume less iron in general, often because they are restricting calories or cutting out/avoiding red meat. "The high baseline level of iron deficiency in women and girls, coupled with the iron losses associated with menstruation and running training, results in a prevalence of iron deficiency in women that approaches 50%." (John Davis again)

FIFTY PERCENT, you guys! That's a lot of lady runners running around with iron deficiency.

4) There are other reasons endurance athletes, particularly runners, go through iron so fast. First there's something called "footstrike hemolysis," which is a fancy way of saying that when you repeatedly slam your feet against the ground for hours and hours, you're actually physically destroying red blood cells. Iron is also lost through sweat, gastrointestinal bleeding (normal for athletes) and, for women, menstruation.

Finally, there's new science that suggests hard workouts cause an iron-blocking hormone called hepcidin to spike. Hepcidin levels seem to peak three to six hours after a hard workout, so if you're doing iron supplementation, you definitely want to avoid taking it during that window.

5) Even if you know the difference between hemoglobin and ferritin, and even if you ask your doctor to specifically look at your ferritin levels, you might still end up getting a false "All good here!" report. Because, again, doctors are used to treating people who are sedentary or near-sedentary, so the "normal" range is established with what works with most of the population--ie, the sedentary/inactive (and certainly non-athletes).

For women, normal ferritin levels are 12-300 nanograms per milliliter of blood (ng/mL). For men, it's 12-150 ng/mL for females. Above these levels is where you can get into trouble with iron poisoning. (Women can get away with higher levels than men because of menstruation.)

The first time I had mine tested, feeling super awful, I think it was 17 ng/mL, and of course the lab & doctor declared me absolutely 100% fine. Which mystified me until I went back to those blog posts written by other women runners and learned that for a lot of them, 30 ng/mL is the bare minimum of not feeling awful, and others don't feel normal unless they're at 45, 60, or even 90 ng/mL!

I did some more actual research about this issue--"normal" ferritin for women runners being significantly higher than the usual "normal" ranges--and took it back to my doctor. He had literally never heard of this idea before. Like never. Like he actually said that maybe I should defer to my coach instead of him re: iron levels because he--the doctor--knew nothing about the specifics of ferritin in women athletes.

I didn't supplement at that point, but with two weeks left before the Eugene marathon, I pretty much started eating red meat and/or beans and/or spinach at every meal. Like until I was nearly actually sick of them. I did start to feel better, but also I was tapering at that point as well, so I'd expect to start feeling less exhausted no matter what. After the race I had my ferritin tested again and it was up to 37 ng/mL. So, success??

I sort of stopped worrying about it after that. As long as I was feeling fairly normal, I figured my ferritin was probably okay.

Until, that is, I was a month out from Boston and feeling like utter crap again. YOU'LL NEVER BELIEVE WHAT HAPPENS NEXT! Actually you probably will, it's pretty predictable.

Next Time: Iron Deficiency, Present Day Edition

Adventures with Iron deficiency, Part 2