Timing Your Iron

By Dr. Cathlin Fitzgerald, PT, DPT, CSCS

Iron deficiency is a common problem, is even more common among endurance athletes. Iron is lost through sweat, urine, the GI tract, and menstruation. Athletes need more iron than the average person; the more efficient the athlete, the more sweat is produced, and so more iron is lost. It has been shown that high intensity and endurance exercise can increase iron losses by 70%. Add in a vegan or vegetarian diet and the risk increases even more because the iron in plants is less absorbable. 

Common symptoms of iron deficiency include a decrease in exercise or athletic performance, general fatigue and low energy, a higher heart rate than typical during exercise, and shortness of breath during exercise. It’s important to remember that these symptoms are more pronounced and more often seen when an athlete has developed iron deficiency anemia. This when the iron deficiency starts to affect the quality of your red blood cells.

Once blood tests confirm an iron deficiency, athletes typically start on iron supplements to help replenish their stores. There is evidence showing that when you take the iron can make a difference. Studies have shown that hepcidin, a protein that regulates iron absorption, increases with exercise. This typically indicates lower iron absorption after exercise. However, a recent study looked at hepcidin levels and iron absorption in 16 endurance trained runners and found that iron absorption - despite some increase in hepcidin - was at its highest during breakfast after a morning run. This indicates there is a small post-exercise window to promote greater iron absorption. 

If you’ve been experiencing any symptoms of fatigue or a decrease in performance, having your iron checked by a doctor is a great idea. If been prescribed iron supplements, remember that timing is everything! Try taking them with breakfast after your morning run to maximize your iron absorption.

McCormick R Moretti D Laarakkers CM. “The impact of morning vs afternoon exercise on iron absorption in athletes”. Med Sci Sports Exerc. 2019; May 1, ahead of print.