Dietary Supplements for Runners: Iron
Guest Post
Contributed by Becca Addison, RD, CSSD
Read Becca’s advice on other dietary supplements:
Becca Addison is a registered dietitian with a specialist certification in sports nutrition. Her resume includes working at Harvard University in varsity athletics. She is also my friend and former professional running training partner!
Iron and Endurance Training
Iron is a nutrient often associated with endurance training. Around 70% of the iron in our bodies is found in hemoglobin, which carries oxygen within red blood cells to working muscles (fun fact - iron is what makes the red blood cells red)!
More oxygen to muscles means more energy to run long distances, because oxygen converts fuel (mainly fats and carbohydrates) to energy. If a runner is low or iron deficient, they’ll become fatigued more quickly because there isn’t as much oxygen available to provide muscles with the fuel they need.
People with Higher Risk of Iron Deficiency:
Foot Strike Hemolysis refers to the breaking of red blood cells that happens with repetitive striking of your feet on the ground. These damaged red blood cells are lost as waste products, reducing the iron pool in the body.
Menstruating women, due to increased blood loss
Athletes running higher mileage, around 30-40 miles per week or more, due to a phenomenon called foot strike hemolysis. Inflammation from hard workouts, such as interval training, may also reduce absorption of iron in the digestive tract.
Those over the age of 65, due to reduced absorption in the digestive tract
Athletes following a plant-based diet, since plant sources of iron are much less easily absorbed than animal sources. To illustrate how iron from plant sources is poorly absorbed, look at chicken vs tofu in the example below.
Tofu contains more iron than chicken, but a much smaller percentage is absorbed.
Testing for Iron Levels
If you’re experiencing symptoms of low iron such as fatigue or a sudden unexplained drop-off in training, and have at least one of these risk factors, you should consider an iron test. If you have at least 2 of these risk factors, I recommend an iron test before starting a training program.
It’s extremely important to get an iron test before beginning supplementation and to regularly monitor blood levels alongside supplementation. Iron overload is a dangerous condition.
There’s a difference between iron-deficiency anemia (low levels of hemoglobin in the blood) and iron deficiency without anemia (where hemoglobin is normal but iron stores, known as ferritin, are low). There is plenty of evidence to suggest that iron deficiency without anemia still impacts performance, so even if your ferritin is in the low end of the normal range, your training could still be negatively affected.
Running performance starts to be negatively impacted when ferritin drops below 30-50 ng/mL, and likely varies based on the individual. It’s important to find a level where you feel your best. Make sure to ask your doctor specifically for ferritin level in your bloodwork. If your iron or ferritin levels are low, ask your doctor for guidance on dosage for supplementing.
Important Note: Acute inflammation from hard exercise can temporarily affect ferritin levels, so avoid having bloodwork done for testing right after doing a hard workout!
Tips for Iron Supplementation:
Choose a ferrous form of iron (ferrous fumarate, ferrous sulfate, or ferrous gluconate), which are best absorbed.
Avoid consuming iron supplements alongside dairy, tea, or coffee - all inhibit absorption.
Like with blood tests, avoid supplementation within 6 hours after a workout due to decreased absorption levels related to acute inflammation.
Take alongside vitamin C, such as a glass of orange juice, because Vitamin C enhances absorption of iron in the digestive tract.
Iron supplements can cause stomach upset (diarrhea and/or constipation). To avoid these side effects, stay hydrated and try taking your iron supplement at night so you sleep through any issues. If you experience ongoing issues, switch to a gentler form called Blood Builder (by Mega Foods.)
There’s evidence that taking iron every other day is just as effective as taking it daily. Talk to your doctor or dietitian about this strategy, especially if you deal with digestive issues.
Be consistent! As part of your daily (or every other day) routine, supplementation typically reverses iron deficiency in 3 to 6 months.
Avoid Contamination in Your Supplements
Make sure your supplements are third-party tested! Supplements aren’t regulated by the FDA, and are often contaminated. Look for NSF Certified for Sport, Informed-Sport, or USP verification on the bottle.
Some third-party tested brands I recommend are:
Thorne
Klean
Ritual
Care/of
Smarty Pants
Garden of Life
Rainbow Light
Olly
Centrum
Mega Foods (especially for Iron)
Nature Made
Are you looking for individualized guidance on anything nutrition related?
Whether it’s learning how to optimize your nutrition and hydration for recovery, understanding how food can impact your performance, or simply taking the stress out of nutrition choices, be sure to find a Registered Dietitian. “Nutritionist” is not what we’re looking for.