Feeling Tired? Check Your Iron Levels
The basic goal of aerobic training is to increase the blood's ability to carry oxygen to working muscles. That’s why it’s called aerobic, meaning with oxygen. Physiology 101 tells us it the red blood cells that carry oxygen. So in essence, aerobic training is about increasing the red blood cell (RBC) volume or hematocrit.
How to Raise Your Red Blood Cell Count
Athletes aim to raise their hematocrit as high as possible, but in legal manners. Indeed, the banned drug erythropoietin (EPO) does just this thing - raises hematocrit so more oxygen is provided to the muscles.
There are a couple ways to raise the RBC volume through training, but both are based around reducing oxygen saturation. Long slow distance increases base fitness by increasing RBC, and minimalist coaches like myself use anaerobic intervals to elicit the same response. Anaerobic work (work done without oxygen) triggers the brain to release erythropoietin from the kidneys. Yes, the same hormone that is illegally injected.
The irony, though, is that while training causes the body to need more red blood cells and to release the hormone to trigger their creation, there is one more building block that is commonly deficient in an athlete’s diet: iron.
EPO doesn’t trigger the release of red blood cells, as such. It triggers the release of erythrocytes that bind with an iron atom to produce a red blood cell that contains hemoglobin. Hemoglobin is the actual oxygen-carrying component of the red blood cell. At the nucleus of hemoglobin is an iron atom. Thus, without iron an athlete cannot produce oxygen carrying red blood cells.
How Much Iron Do I Need?
Plants vs. Red Meat
- 400g of Broccoli is a lot - close to five cups. 100g of red meat is very little. Most vegetarians don’t eat this much broccoli every day and the average serving of red meat is closer to 300g.
- Bioavailability. Just because a food contains a nutrient doesn’t mean your body can absorb it. Vegetable-sourced Iron (also called non-heme iron) is only around one quarter as well absorbed as meat-based iron (heme iron). To match a 300g piece of grass-fed beef, you would need to eat close to five kilograms of broccoli.
Seek out good, bioavailable iron sources. For vegetarians, choose chickpeas, legumes, and eggs. For omnivores, include grass-fed red meat in your diet.
So plants are not only a poorer source of bioavailable iron but also block its absorption, making the iron even less available. Phenolic acid found in apples, peppermint, and some herbal teas, and tannins found in black teas, coffee, cocoa, spices, walnuts, and fruits such as apples, blackberries, raspberries and blueberries all have the ability to inhibit iron absorption. Polyphenols have not been shown to have the same inhibitory effect on heme iron.
The ultimate irony is that for those training to become an Ironman they are commonly missing just that. So it’s time to put the iron back in Ironman.
1. Hurrell RF., Reddy M., Cook JD., "Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages." Br J Nutr. 1999 Apr;81(4):289-95.