Hello Runner,
Welcome back to your weekly moment of endurance nutrition!
Happy Weekend!
How was your week?
I had a good week. While I took it easy over the Easter holiday, I also got a lot done.
I kept up with my training as usual, and on Monday (which was a holiday here in Catalonia), I worked and studied as usual.
I’m continuing to improve my times on the track, which makes me really happy. But I’m really missing going for a long run, hehehe.
Today’s topic is iron deficiency, absorption, and related topics.
I touched on this a while back here in the newsletter, but today I’m going to explain more about this mineral that’s so important for us runners.
Iron is a core component of haemoglobin, the protein inside your red blood cells that binds to oxygen and carries it from your lungs to your muscles. It's also part of myoglobin, which stores oxygen in muscle tissue itself. On top of that, iron plays a role in cellular energy production. So when iron drops low, everything downstream suffers: your pace, your breathing, your recovery, your mental sharpness mid-run.
Ferritin is the storage form of iron in the body, and it's one of the most useful markers to track. You can still have normal haemoglobin levels while ferritin is quietly draining. That's the stage many runners live in without realising it, feeling off but not technically anaemic (the last stage of iron depletion).
Stages of iron depletion
The gradual loss of iron from the body due to inadequate dietary intake is commonly referred to as iron depletion. This condition is believed to progress through several stages, each with different pathophysiological factors and diagnostic criteria.
Normal iron stores are indicated by a serum ferritin concentration >30 μg/L (female)/ >110 μg/L (male) and a serum haemoglobin concentration >120g/L (female)/ >140g/L (male)
Low iron stores (iron depletion) are indicated by a serum ferritin concentration <30 μg/L and a serum haemoglobin concentration >120g/L (female)/ >140g/L (male)
Iron deficiency is indicated by a serum ferritin concentration <12 μg/L and a serum haemoglobin concentration >120g/L (female)/ >140g/L (male)
Anemia is indicated by a serum ferritin concentration <10 μg/L and a serum haemoglobin concentration <120g/L (female)/ <140g/L (male)
Anemia in athletes/runners may be caused by low energy intake, insufficient iron intake to maintain iron stores, or low meat consumption (the most readily available dietary source of iron).
Following a low-energy availability diet increases the risk of iron deficiency, as iron intake is more likely to be insufficient to meet the body’s needs.
→ The general recommendation for adult men is around 8 mg per day, while women of menstruating age need significantly more, around 18 mg daily. But runners are not the general population.
Endurance sport increases iron losses through sweat, through the gastrointestinal tract, and through a process called foot-strike haemolysis, where red blood cells are literally damaged by the repeated impact of running. Because of this, some sports nutrition researchers suggest that runners, particularly female runners, may need up to 30-70% more than standard daily recommendations.
Heme and Non-heme Iron
Not all dietary iron is created equal. This is where the heme versus non-heme distinction matters enormously.
Heme iron comes from animal sources: Beef, lamb, liver (beef/chicken), pork, turkey, veal, Clams, oysters, mussels, sardines, tuna, and mackerel.
It's absorbed efficiently, with absorption rates typically between 15 and 35%.
Non-heme iron comes from both animal- and plant-based foods. Sources: Lentils, chickpeas, beans (white, red, kidney), tofu, edamame, dark leafy greens like spinach, kale, swiss chard, beet greens, along with broccoli and sweet potatoes. Also, sesame seeds, pumpkin seeds, hemp seeds, cashews, and fortified foods like breakfast cereals, bread, and pasta.
It's absorbed much less efficiently, often only 2 to 20%, depending on what else is in the meal.
If you're vegetarian or vegan and running regularly, you're working with a smaller iron budget and need to be particularly strategic.
Absorption Window
Here's a finding that many runners don’t know about: There is a window for iron absorption that extends from before exercise until no later than 30 minutes after exercise. Research suggests that hepcidin, a hormone that regulates and can suppress iron absorption, is at its lowest right after a session.
Ideally, you should eat iron-rich foods in the morning or no later than 30 minutes after exercise.
If you run in the morning, it’s best to eat these foods in the late afternoon or well after your workout!
STRATEGIES
How to increase iron absorption from the diet
Since iron absorption from food is relatively inefficient, there are a few strategies for increasing its absorption in the diet. These include:
Include foods rich in vitamin C (citrus fruits, kiwi, strawberry, broccoli, spinach, kale, bell peppers (especially yellow), cabbage, cauliflower, brussels sprouts, tomatoes, sweet potatoes) → increases absorption by 2–9 times
Cooking in cast-iron cookware can increase the iron content in food by ~15%
Eat iron-rich foods from animal and plant sources together → this improves absorption by ~1.5–3 times
Soak legumes or add vitamin C to “block” the effects of phytic acid (which inhibits iron absorption).
Time your coffee and tea strategically. Wait ~60 minutes before and after meals to drink your coffee or tea. This is especially relevant at breakfast, which is often when runners eat iron-containing foods like eggs, fortified cereals, or wholegrain toast.
If you're plant-based, build iron redundancy into your meals. Spread iron-containing foods throughout the day. Example: lentils at lunch, fortified oats at breakfast, pumpkin seeds as a snack, and edamame in your dinner.
Avoid
Consuming large amounts of calcium-rich foods (milk, cheese, yogurt, etc.) with iron—rich foods. Doses of 300–600 mg of calcium (~2 glasses of milk) can reduce iron absorption by 20–50%
Remember that monitoring haemoglobin and serum ferritin levels is recommended for runners (especially female athletes) to prevent deficiencies.
Many standard blood panels check haemoglobin but not ferritin. You can have a "normal" haemoglobin result while your iron stores are already depleted.
This week, take a look at your meals and see if they include iron-rich foods. Also, check to see if you’re doing what you need to do to increase your iron absorption.
Is there a cup of tea or coffee? Swap it to before or well after the meal. Is there a vitamin C source? If not, add one.
Just one week of this small, but intentional shift can make a measurable difference to how much iron your body actually uses from the food you're already eating.
Product of the Week
This week's Product of the Week is the Xtratus Super Beet.
This is a supplement I used for a while, and I noticed a big difference in my performance.
The beetroot nitrate and watermelon citrulline work together as complementary vasodilators, improving the flow of oxygen and nutrients to the muscles.
→ It’s best to take it 1.5 to 2 hours before exercising. And avoid taking it right before brushing your teeth, because it destroys the beneficial bacteria in your mouth necessary to convert dietary nitrates into nitric oxide.
Of the few nitrate supplements I've tried, this was one of the tastiest. It tastes like watermelon juice.
Since I’m a partner with Xtratus, they gave me a discount coupon to share with my clients and readers. Coupon: ANAPAULAALONSO10
Track of the Week 🎧️
This week's Track of the Week is a remix of a really old classic. I discovered it the other day and loved it. This one’s sure to liven up your summer runs!
I’ve chosen Jamaican (Bam Bam) by HUGEL, SOLTO
Any questions or something you would like to share, drop me an email
Wishing you a great weekend and week ahead!
Here’s to health and good runs⚡️
Ana Paula Alonso