As a sports dietitian (CSSD), I talk about iron values, iron sources and iron absorption, frequently. Adequate iron levels, for all athletes, but especially for endurance athletes, are critical to produce oxygen transporters, hemoglobin and myoglobin. As I describe to athletes, if you don’t have enough iron, then you don’t have enough oxygen, and NO ONE wants to be in oxygen deficit when they are trying to train and recover optimally. For the science geeks, hemoglobin carries oxygen from the lungs to bodily tissues and myoglobin is within the muscle cells patiently storing oxygen for use when called upon during activity.
Athletes are particularly susceptible to iron deficiency anemia due to low consumption of highly absorbable forms of iron, stress, overtraining or even hemolysis, which is the breaking of blood cells when an athlete’s foot hits the ground (impact forces) or during the constriction of blood vessels during heavy training (1). The scary news is that it is suggested that 20%-50% of female athletes and 4% to 50% of male athletes have depleted iron stores, which suggests that many athletes could benefit from an intervention that addresses this issue (2). Obviously, females are more susceptible than men due to monthly menses and some sports are more at risk than others, namely those in endurance sports such as swimming, running, rowing, triathlon, soccer and basketball (3).
Additionally, athletes who partake in a vegetarian or vegan lifestyle, have low overall calorie consumption, low animal protein consumption, and those who have medication interactions that lead to less iron absorption are also at higher risk. These athletes should be monitored more closely by health professionals and coaches for adverse symptoms.
Symptoms of Poor Iron Stores
- · Early exercise fatigue
- · Shortness of breath
- · Decreased training adaptations
- · Increased RPE (rate of perceived exertion)
- · Delayed wound healing
- · Poor condition of skin, hair or nails
- · Difficulty swallowing or sore tongue
Requesting blood work can seem daunting. Ideally, you will work with a professional, such as a certified sports dietitian in conjunction with your physician, to make sure that you not only order the correct markers of iron deficiency, but to also help you interpret this information. Some key things to note are that blood should be drawn 24 hours post-training or during a recovery period to make sure it is as accurate as possible.
The athlete should have blood and urinary markers such as:
- · CBC (complete blood count)
- · Serum ferritin
- · Serum iron
- · Transferrin saturation
- · TIBC (total iron binding capacity)
- · Reticulocytes
- · Urine specific gravity (USG)
The intervention will depend on the results of this blood work and the specific lifestyle factors of the athlete. Iron supplementation should never be blindly administered, as it’s toxic in high amounts or with specific conditions.
Athletes should note, there are two types of iron within food sources, heme and non-heme, with heme iron being much readily absorbed by the body. Heme is found in animal sources such as lean beef, eggs, lean pork/ham, tuna, salmon and chicken breast. Non-heme iron is found in plant foods and its absorption can be improved when consuming sources of vitamin C concurrently (think strawberries, oranges, peppers or tomatoes). The problem is most people think spinach is wonderful for iron, and while it’s a good non-heme source, certain types of fiber (oxalates) inhibit the absorption of non-heme iron, so you’re going to be hard pressed to make those sources a significant part of your diet and still meet your needs.
The DRI (dietary reference intake) for iron is currently 18mg/day for females ages 18-50 years, and 8mg/day for males. This is the amount needed for those who already have adequate iron status, not for those who are found to be deficient and require repletion. Specific populations (i.e. pregnancy, lactation, vegetarians and those out of the age ranges listed above) often require additional iron. Obtaining this amount won’t happen by accident, so consumption of lean beef (3.5oz per serving) is an excellent option to increase your daily iron and meet your protein needs. An easy salad is spinach, sirloin tip steak, walnuts, cranberries, blue cheese and a raspberry or balsamic vinaigrette. I have it often and feel full and satisfied from the fiber and protein, which helps me stay on track! Just the beef portion alone has 3.8mg, so you’re headed toward your daily needs and it tastes wonderful as well.
Other sources of heme-iron include oysters (surprised on that one? I was!), eggs, lean pork/ham, tuna and salmon or chicken breast. I hope you enjoyed learning a bit more about your iron needs as an athlete! Work with a sports RD to get some specific advice and tailor your plan to meet your individualized needs!
1 (1) Selby, G. B., & Eichner, E. R. (1986). Endurance swimming, intravascular hemolysis, anemia, and iron depletion. The American Journal of Medicine,81(5), 791-794. doi:10.1016/0002-9343(86)90347-5
(2) Malczewska, J., Raczynski, G., & Stupnicki, R. (2000). Iron Status in Female Endurance Athletes and in Non-Athletes. International Journal of Sport Nutrition and Exercise Metabolism,10(3), 260-276. doi:10.1123/ijsnem.10.3.26
(3) Hinton, P. S. (2014). Iron and the endurance athlete 1. Applied Physiology, Nutrition, and Metabolism,39(9), 1012-1018. doi:10.1139/apnm-2014-0147