When people think of nutritional deficiencies, they probably picture women with goiters due to lack of iodine or other newsworthy examples. In reality, the most common nutritional deficiency in the United States is iron deficiency. Iron Deficiency (ID) is especially common in endurance athletes, especially female athletes.
|Start of 2013 Roy Griak Invitational Cross Country Meet at |
the University of Minnesota. Photo courtesy of Jennifer Larson.
Iron is the metal in humans that allows oxygen to be carried in our bloodstream to all of our other organs. Without enough iron, less oxygen is taken to the muscles and other organs that need it. People with anemia (iron deficiency) may experience fatigue, weakness, and dizziness. Scientists Irena Auersperger, from the University of Ljubljana in Slovenia, Branko Skof and Bojan Leskosek, both from the University Medical Centre in Ljubljana, Slovenia, Ales Jerin, from the University Clinic Golnik in Golnik, Slovenia, and finally Mitja Lainscak, from Campus Virchow-Klinikum in Berlin, Germany asked how iron levels affect performance levels in female runners and whether or not intensified training impacts various iron parameters.
Fourteen moderately active women were chosen to participate in the study. In order to be enrolled they had to have regular menstrual cycles, eat animal products on a regular basis, and not be taking forms of medication except birth control. Each woman was put into one of two groups based on her ferritin levels. (Ferritin is a protein that stores iron). Anyone with ferritin levels greater than 20 micrograms per liter was put in the Normal group (for normal iron stores). Anyone with ferritin less than or at 20 micrograms per liter was put into the Depleted group (for depleted iron stores).
The study took place during a training period leading up to the International Ljubljana Marathon. During the eight week training period, runners had routine tests consisting of a 2400 meter (1.5 miles) time trial on a standard 400 meter outdoor track. Blood samples were taken at three different times: once before the eight week training period, once after the training period, and once more ten days after the marathon. These measurement times will be referred to as baseline, training, and recovery, respectively. Height, weight, and body fat percentage were measured during baseline and at recovery. Each woman then ran on a treadmill so researchers could measure her maximum speed, maximum oxygen consumption (VO2 max), and heart rate. Blood samples were taken at baseline, training, and recovery points to measure various blood parameters and iron parameters.
Both Normal and Depleted groups had similar body measurements, VO2 max, and heart rates. Both groups had improvements in their endurance measurements, however, only the Normal group had endurance improvements that could be documented as significant while the Iron Deficient group’s endurance improvements were less. By the end of the experiment, most of the runners were anemic. Both groups experienced a decrease in iron levels during the training and recovery periods compared with the baseline levels. Overall, both groups’ iron levels decreased in all areas during the training phase, even though they were both getting stronger and faster. The group that started out with lower iron levels did not show as great of an improvement as the group with the normal iron levels at baseline. Even after the 10 day recovery period, iron level parameters were still considered low. With this data, the researchers agree that Iron Deficiency decreases performance levels of female athletes.
Even though most people consider running to be a very healthy pastime, it can have undesired negative effects as well. All endurance athletes, especially female athletes, should have their iron levels checked regularly, and should make a conscious effort to incorporate iron into their hopefully already healthy diet by eating any enriched grains and a healthy amount of red meat. With consent of a physician, iron supplements can also be a good way to keep iron levels in check.
Auersperger I, Škof B, Leskošek B, Knap B, Jerin A, & Lainscak M (2013). Exercise-induced changes in iron status and hepcidin response in female runners. PloS one, 8 (3) PMID: 23472137