Iron + The Athlete: Considerations for Intake and Absorption

I took my first formal nutrition class back in 2014. At the time, I already had a ton of nutrition knowledge, both from on-the-job training and from personal study, but I was beginning to realize I wanted to shift my career from public health into individual nutrition.

As a female and athlete (with digestive issues), I had always struggled with iron, despite eating a fairly high iron diet. At first, I also ate some red meat, and in my nutrition class, we had to complete a three-day food log and perform a nutritional analysis. I was easily meeting the recommended dietary allowance (RDA) for iron. When I asked my instructor about it, a locally practicing registered dietician, she told me, “If you’re consuming the RDA in iron,  you should not have low iron status.”  

That conversation turned out to be a good jumping off point for wanting to know a whole lot more about nutrition, and nutrient and lifestyle interactions.

If you’re an athlete (male or female), and you’ve ever wondered about what all the hype is on iron, or why you have low iron, or what exercise has to do with iron regulation and absorption, this article is for you.

The Role of Iron and How Iron Deficiency Impacts Athletic Performance

First let’s review what iron does in the body. When we speak about iron, we’re often speaking about it in the context of iron-deficiency anemia. There are many reasons for anemia, not just low iron stores, but iron-deficiency anemia is the most common. Anemia at its most literal means “without blood.” And that’s where we start to talk about iron (though again there are other nutrient depletions that can also cause anemia). 

Iron is an essential part of oxygen transport and energy production at a cellular level, and is important for cognitive and immune function (1,2). Hence the reason you feel fatigued when your body is without iron. Note that low energy is also a feature of many nutrient deficiencies since many nutrients are involved in cellular energy production.

For endurance athletes, iron is dually important because it is used for multiple metabolic pathways, including 1) it is used for oxygen transport to the exercising muscle and 2) the production of ATP (energy) is highly reliant on iron.  

Common symptoms of compromised iron status include fatigue, lethargy, negative mood, and poor performance during endurance exercise. 

A Hormone Called Hepcidin and its Impact on Iron Absorption  

Hepcidin is an inflammatory and iron-regulatory hormone that increases for 3 to 6 hours after exercise. This is likely a result of the exercise-induced inflammatory response, and associated increases in an inflammatory cytokine, interleukin-6 (IL-6). Increases in hepcidin result in a decrease in iron absorption as well as decreases in recycling iron from the gut.  

So there’s likely a window of time following exercise where the body has altered iron metabolism. 

Who is at risk for iron deficiency? The mechanisms that influence iron absorption in athletes

Traditionally, we think of compromised iron status as something that females suffer from. This is because women in their menstruating years generally lose iron through blood loss each month; whereas men should not be losing blood. However, active women are estimated to be twice as likely to present with Iron Deficiency Non-Anemia (stage 2 of iron deficiency) than sedentary, non-active women. Among athletes, we see much higher iron deficiency rates than in the general population with estimates of greater than 50% of female athletes and up to 30% of male athletes having compromised iron stores (1).

Both testosterone and estrogen can influence iron metabolism because they suppress hepcidin (more on this hormone above). When women are exercising at a high training load, this may result in an altered hormonal profile, with gonadotropin-releasing hormone (GnRH), which is a sex-hormone precursor, being suppressed. Consequently, luteinising hormone (LH), follicle stimulating hormone (FSH), and then estrogen will be suppressed. So lower estrogen leads to higher hepcidin (or at least less suppression of hepcidin), and thus more difficulty in absorbing iron. 

Likewise, the same result can happen in males with a high training load, with gonadotropin-releasing hormone being suppressed, and consequently suppressed testosterone, and less suppression of hepcidin. In turn, chronically low testosterone in males may be linked to higher hepcidin levels, potentially impairing iron regulation. 

Another variable is relative energy deficiency- what I call not eating enough for one’s activity level. Overall low energy availability (LEA) and energy intake may relate to either an overall deficit in dietary iron intake, and/or a dysfunction in iron absorption from the foods that are consumed. 

Further, we’re also finding that the makeup of one’s microbiome also affects iron absorption, with iron-deficient individuals lacking lactobacilli species–a key species often cited with good health. Many other bacteria also require iron for growth (3).

Otherwise, vegetarian and vegan / plant-based diets can also impact iron absorption and stores since non-heme plant sources of iron are more difficult to absorb. A big one though, is the general state of your digestion. You have to have good digestive function to assimilate the nutrient.

Finally, some good news: the inflammatory response following exercise can be reduced after long exercise bouts of two hours or longer by consuming carbohydrates during exercise. Eating during exercise decreases the depletion of glycogen stores in the muscle (2), and ingesting carbohydrate during exercise has also been shown to improve the recovery response from long/high intensity efforts.

The Stages of Iron Deficiency:

Stage 1: Iron Deficiency: Iron stores in the bone marrow, liver, and spleen are depleted, indicated by ferritin values less than 35ug/L, Hemoglobin values > 115 g/L, (11.5) and transferrin saturation >16%

Stage 2: Iron-Deficient Non-Anemia: Red blood cell production decreases as the iron supply to the bone marrow is reduced, indicated by ferritin values less than 20ug/L, Hemoglobin >115 g/L (11.5), and transferrin saturation < 16%

Stage 3: Iron Deficiency Anemia: Hemoglobin production falls, resulting in anemia, indicated by ferritin values less than 12 ug/L, Hemoglobin <115 g/L, transferrin saturation less than 16%. 

From current research, it appears that depleted iron stores (in stage 1) have minimal or no impact on physical performance, but this is likely particular to you as an individual–some athletes will notice the impact sooner.

What You Are Eating in Your Diet and Iron Status

The timing, amount and source of iron from your diet, in combination with the overall composition of the diet are all important factors to consider when looking at iron status. The most easily absorbed source of iron is heme iron (from meat).

The presence of Vitamin C can enhance non-heme iron absorption, but vitamin C is destroyed by heat (and light), so cooking a vitamin C-rich food into a dish will likely not help much. A couple squeezes of citrus juice at the end of cooking when the food is on your plate can be an effective method to get around this.

Otherwise, polyphenols, phytates, oxalates, calcium, zinc, copper, and vitamin E, which are all part of many nutritious, plant-rich diets and in particular are in whole grains, legumes, leafy greens, and tea and coffee, can decrease the amount of non-heme iron that is absorbed in a meal. Suddenly, your (or my) quinoa salad bowl with nuts, seeds, lentils, spinach and other dark leafy greens, and tahini or almond sauce is not a recipe for a hearty, iron-absorptive meal. Note, these are foods that are frequently on the high-in-iron list! And there are ways to prepare them to make their iron more absorbable, such as soaking, sprouting, fermenting, etc.

Want to Know More?

Within my nutrition practice, I specialize in endurance athletes and digestive imbalances. If you’ve struggled with chronically low iron, or recently have experienced it, I encourage you to reach out to me for more personalized support about how to boost iron around your exercise load.

References:

1). Sim, M., Garvican-Lewis, L.A., Cox, G.R., Govus, A., McKay, A.K.A.,…and Peeling, P. (2019). Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology, 119: 1463-1478. https://doi.org/10.1007/s00421-019-04157-y

2). McKay, A.K.A., Pyne, D.B., Burke, L.M. and Peeling, P. (2020). Iron Metabolism: Interactions with Energy and Carbohydrate Availability. Nutrients, 12: 3692. https://doi.org/10.3390/nu12123692

3. Frame, L. (2021, October 7th). Mixed Diet and the Microbiome- Challenges with Complexity. Linus Pauling Institute Diet and Optimum Health Conference, Corvallis, OR, United States. 

A simple digestion tip for when you’re struggling

The last few weeks, I’ve dropped back into a pattern I always wish to avoid. Feeling those frequent low-grade, lower belly aches, and sometimes feeling simultaneously heavy and like a giant airy balloon resides in my midsection. It’s most noticeable two to three hours after a meal, when the food has left my stomach and reached my small intestine, and around the time I’m either about to begin or am in the first few miles of my daily run or workout. 

Not so enjoyable.

This used to be my norm. It used to be so much my norm that if it were just these mild symptoms, I wouldn’t have noticed it  or done anything about it at all. I wasn’t quite as in tune with my body then, you could say. But then it became chronic. And got a lot worse before I figured out, with help, how to make the sour, painful digestion situation better.

So when you come to me and say, “I can’t believe I’m telling you this,” well, I know what you’re talking about and it’s not something that should be hush hush or shameful — at least not when you’re talking to a nutritionist. 

In the interest of providing some guidance before you start removing random foods, purchasing specialty digestive products or just holding your belly and whimpering / running to the bathroom, here’s one quick tip to improve digestion for you. 

Try One Simple Shift

It’s a shift that worked for me the last couple weeks as I switched from eating more cold/raw summer meals to putting those same foods in meals and gently cooking them.

That’s right. That’s the shift. 

Just switch to eating all your meals warm and gently cooked. 

It’s simple but especially in the end-of-summer warm days, you might have to remind yourself daily, if not with every meal, to just heat everything up. I don’t heat up some foods, and eat others raw, like including a side salad with a meal. Warm all of it up. Do a quick 30 second to 1 minute sauté of your salad ingredients in your vinaigrette in a sauté pan, if that’s easiest. Oh, and chew it all well.

Think of your digestive ability like a campfire. Too hot and everything burns up and gets singed too quickly, like that marshmallow or hot dog you’re roasting. Too cold and nothing really cooks at all. It just smolders along half-heartedly. That smoldering is what we’re trying to avoid here, since it’s most common when you struggle with symptoms of the lower GI.

If you’re interested in more simple digestion shifts, I wrote a mini-guide for improved digestion featuring no products, special foods, or diets which you can download. Or check out the last few blog articles on improving digestion for more ideas.

Veggie Rainbow Cool Noodles

In a quest to cook more in community, and educate in a hands-on format again, I’ve been leading routine cook-a-longs this summer. I’ve been cooking both with my local running group and as part of my public health nutrition role, my side gig when I’m not working one-on-one with nutrition clients.

I love cooking with both groups–but especially the cook-a-longs with my running ladies because we share similar interests and chat more as we’re making the recipes. And because I get to choose recipes that I routinely make in my everyday and know will make meals and workout recovery easier for others.

This is one such recipe that we made together last week.

It’s a cool noodle dish, served either warmish or at room temperature, but ideally not truly ‘fridge-cold’ or with raw vegetables, because that makes it extra difficult to digest. At a time (summer / hot weather) when our natural digestive ability is already weaker.

It features an Asian-inspired sauce and is kept super easy and quick by utilizing a protein and carbohydrate source in one with legume-based pasta noodles. If you don’t prefer tahini, choose almond butter instead. There are several legume-based pastas on the market. Banza is a good one. If you don’t prefer that, you can add two cups of edamame, your choice of other protein such as grilled fish, chicken, or tofu, and use a whole-grain noodle, such as brown rice noodles or whole-wheat fettuccine. 

Happy cooking and summer training / adventuring / eating / digesting! :)

Veggie Rainbow Cool Noodles
Prep:  15 minutes  | Cook: 15-25 minutes  | Serves: 4

Ginger Turmeric Tahini Sauce:
¼ cup tahini
½-inch fresh ginger, finely grated
1 Tbs. low-sodium tamari or soy sauce
½ tsp. turmeric
2 Tbs. lime juice
1 tsp. pure maple syrup
1 Tbs. light miso 

Noodle Salad:
8 oz. chickpea or legume-based noodles
3-4 large carrots (about 500 grams), sliced thin
1 bunch (240 grams) radishes, sliced
2 cups green peas, fresh or frozen
½ cup (packed) cilantro, plus more for garnish
Toasted sesame seeds, for garnish

  1. Make the sauce: Mix the sauce ingredients, along with 4-8 Tbs. water until completely smooth. Taste and adjust seasonings as needed and then set aside. 
  2. For the Noodles: Bring a pot of water to a boil. Add the noodles and any hard vegetables (such as carrots or radishes) and cook half way through. Add the peas and any softer vegetables, and cook the remaining few minutes until the pasta is al dente. Drain and rinse with cold water to stop the cooking process. 
  3. In a medium-serving bowl, toss the pasta and vegetables with the sauce and cilantro. Top with some toasted sesame seeds and serve. 

Notes: Change up the vegetables depending on what is in season near you! When you vary it up, choose one to two root vegetables or starchy vegetables and one or two leafy green vegetables or more pungent vegetables.
Roots/Starchy Examples: Peas, fresh corn, carrots, summer squash, zucchini (spiralized to add to the noodles (not in replace of!) is what I’ve done in the photo above)
Green/Pungent Examples: Broccoli, cabbage, kale, spinach, radishes, daikon radishes (what I’ve used in the photo), asparagus

Want to Know More?

Within my nutrition practice, I specialize in digestive imbalances, often within endurance athletes. When we’re experiencing chronic GI distress, fatigue, and/or malabsorption of foods and nutrients, there will often be imbalances in several systems of the body simultaneously. I shared more about this topic in the nervous system’s role in part 1, the immune response and subsequent inflammation in part two, gut microbes and dysbiosis in part three and the importance of chewing our food in part four. Check those out or reach out to me for more personalized support for gut healing, increased energy, performance, and feeling good in your everyday life.