Impact of iron depletion without anemia on performance in trained endurance athletes at the beginning of a training season: A study of female collegiate rowers
 
 
Journal Title (Medline/Pubmed accepted abbreviation):  Int. J. Sport Nutr. Exerc. Metab.
Year: 2012
Volume: 21
Page numbers: 501-506

Summary of background and research design:
Background: Iron deficiency is one of the most common nutrient deficiencies in the US, and is higher among women, especially female athletes. Among pre-menstrual women in the US, anemia affects 3-5% and iron-deficiency without anemia affects about 16%. Rowers train at 75-80% of their VO2max, where iron is essential for oxidative metabolism.

Hypothesis: Iron deficiency with and without anemia decreases performance.

Subjects: Collegiate rowers were recruited over 3 seasons from 5 colleges. There were 165 who completed the study. They were 19.7 ± 1.2 yrs old.

Experimental design: observational

Protocol: The participants completed a questionnaire about demographics, dietary supplement use, health, menstruation status, physical activity, height, weight, and best time to complete a 2 km simulated race from the previous season (2-3 mos prior). Best times were validated in a subset of the rowers (n = 48). To measure iron status, a fasted blood sample was acquired and analyzed for hemoglobin, hematocrit, red blood cell count, serum ferritin (sFER, a marker of iron stores), and soluble transferrin receptor (sTfR, elevated in iron deficient anemia).

Summary of research findings:
  • There were 16 iron-deficient anemic rowers (10%).
  • Of the non-anemic rowers, 33% were iron deficient.
  • For rowers with sFER < 20.0 µg/mL (iron deficient), their average 2 km time was 21 sec slower (combined average 469 ± 25 sec).

Key practice applications

Iron deficiency is very common among female college athletes and it may be hindering their performance. It may be useful to screen athletes at the beginning of the season to identify those who have or are at risk for iron deficiency so they can adjust their diets accordingly. All female athletes should be aware of the prevalence of iron deficiency and assure they consume an iron-replete diet.

Limitations

Most of the data here are self-reported (best time trials, height, weight, etc.), which is typically not as accurate as direct measurements. Also, the authors have found a correlation between iron status and time trial times but did not determine causation. For example, those that had low iron status may have other dietary/lifestyle factors that are causing their slower performance that is not related to iron status. In other words, increasing iron status will not guarantee faster rowing times.

It would have been interesting if the authors performed a correlation between iron status and performance times. Is there a "threshold" iron status that will facilitate (or prevent) certain performance characteristics?

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