Feeling unusually tired on your runs? Struggling to hit paces that once felt comfortable? Before assuming you need to train harder, it may be worth looking at your nutrition. Two common but often overlooked concerns for female runners are iron deficiency and Relative Energy Deficiency in Sport (RED-S). Both can quietly impact performance, recovery, and long-term health, and female endurance athletes are at higher risk because of the unique demands of training and menstruation.
Iron is essential for producing hemoglobin, the protein in red blood cells that carries oxygen from your lungs to your muscles. Without enough iron, your body can’t deliver oxygen efficiently, making even easy runs feel difficult. Female runners are especially susceptible to low iron because of menstrual blood loss, increased iron needs from endurance training, and small amounts of iron lost through sweating, the digestive tract, and the repeated foot strikes of running. Early signs of iron deficiency may include unusual fatigue, shortness of breath during exercise, decreased performance, difficulty recovering, headaches, or feeling cold more often than usual. Left untreated, iron deficiency can progress to iron-deficiency anemia, which further reduces endurance and overall well-being.
RED-S occurs when an athlete consistently consumes fewer calories than their body needs to support both daily life and training. While many people associate it with eating disorders, RED-S can also happen unintentionally. Busy schedules, increased mileage, or trying to “eat clean” without increasing calories can all result in low energy availability. Over time, this energy shortage affects nearly every system in the body. It can slow metabolism, impair recovery, reduce bone density, weaken the immune system, disrupt menstrual cycles, and increase the risk of stress fractures and other overuse injuries. Performance often suffers long before an athlete realizes what is happening.
The good news is that both iron deficiency and RED-S are preventable with proper fueling. Female runners should prioritize a balanced diet that includes enough total calories along with iron-rich foods such as lean red meat, poultry, seafood, beans, lentils, tofu and spinach. Pairing plant-based iron sources with foods rich in vitamin C, such as berries, oranges, bell peppers, or tomatoes, helps improve iron absorption. If you suspect low iron, don’t start a supplement without talking with your healthcare provider. A simple blood test can determine whether supplementation is needed, and too much iron can also be harmful.
Food is not just fuel for today’s workout. It is what allows your body to recover, adapt, build stronger muscles and bones, and continue enjoying the sport you love for years to come. Eating enough is an essential part of training. When you consistently give your body the energy and nutrients it needs, you’ll recover better, perform better, and reduce your risk of injury along the way.
Sources
- American College of Sports Medicine. Nutrition and Athletic Performance (joint position statement with the Academy of Nutrition and Dietetics and Dietitians of Canada).
- International Olympic Committee. IOC Consensus Statement on Relative Energy Deficiency in Sport (RED-S), 2023.
- Runner’s World: Low Iron Sucked so much Joy out of my Running