Running Into the Ground: Iron Basics
Reasons Why Runners are Often Low in Iron:
1. Foot Strike Hemolysis—red blood cells are destroyed by runners’ feet pounding on the ground. You literally squish them as you strike the ground. This loss can be even more intense at altitude.
2. Sweat & Urine—small amounts of iron are lost in sweat and urine and these amounts can add up over time and worsen in hot weather.
3. GI & Menstrual Bleeding—small amounts of iron are lost due to bleeding in the gastrointestinal tract that is common with intense training/racing, while larger amounts can be lost through a regular menstrual cycle. If your cycle is causing you to lose more significant amounts of blood due to an extended length, heavier flow or increased frequency, you should report this to your doctor so that she can try to find the cause.
4. Low Iron Intake—runners who follow the traditional high-carb/low-fat endurance diet often do not consume much red meat, which is the best absorbed source of dietary iron. Many runners also tend to under eat in an effort to maintain an artificially lower weight. There is evidence that this type of calorie restriction lowers metabolic functioning and over the long term may lead to a sluggish thyroid or hypothyroidism.
Key terms:
Hematocrit— the percentage of red blood cells in the blood
Ferritin— the body’s stored iron (primarily in bone marrow, liver, and spleen)
Iron-Deficiency Anemia—clinically low hemoglobin or hematocrit levels
(B12 deficiency can cause another type of anemia, more common in vegetarians than meat eaters because B12 is difficult to get from a vegan diet)
Iron Depletion—low ferritin levels (for running purposes 30)
What exactly is ferritin again?
For one thing, different people seem to require different levels to feel good. One athlete may perform best as long as her ferritin is over 40, while another may require double. When fine-tuning for performance enhancement, it is best to track ferritin levels over time, that way you can get a baseline level of what might be normal for you. Unfortunately, few people think to go in for blood tests when they are feeling fine. Some sports medicine docs and coaches like an athlete’s ferritin to be above 100. It is commonly accepted in the running community that a score under 30 means you should be pumping some iron into your system, in whatever form necessary.
Serious female runners should have their iron levels checked a minimum of twice (preferably four times) per year. Competitive male runners should be tested annually, and those with a history of iron depletion (or vegetarians) should be tested at least twice per year. To ensure consistent results, always have your blood tested before running (i.e., when you are well-hydrated), because dehydration will make your iron levels appear higher than they are. Again, the major iron status tests of interest to runners are: hemoglobin, hematocrit, red blood cells and ferritin. And, depending on how savvy your doc is, you may have to specifically request the ferritin to be checked. Unfortunately, it is still not a commonly performed test by many family practitioners.
More on iron supps and common signs of deficiency in another post.
