Friday, May 16, 2014

Iron and Exercise Performance

Iron status is usually the last thing athletes think of when exercise performance is the topic. However, an iron deficiency can actually impair performance. In short, iron gives hemoglobin (a protein in red blood cells) and myoglobin (a protein in heart and skeletal muscles) the ability to carry oxygen. When an iron deficiency is present, oxygen delivery to tissues such as the muscles becomes limited. This can result in shortness of breath and fatigue – especially with exercise. Therefore, iron status plays a large role in exercise performance.
Iron-deficiency anemia is not as frequent in athletes as suboptimal serum ferritin levels – the amount of iron stored in the body. All athletes can be prone to suboptimal serum ferritin levels, but women of reproductive age are at a larger risk due to menstrual blood losses and diets deficient in iron.
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Iron can be obtained in the diet from heme or nonheme sources. Heme iron is present in meat such as beef, pork, and seafood. Whereas, nonheme is present in select plant foods like spinach and kidney beans. Unlike the readily absorbed heme iron, nonheme iron absorption is hindered by several dietary factors. For example, the oxalic acid found in spinach or the polyphenols in tea or coffee bind nonheme iron and reduce its absorption.
However, when iron losses – from menstrual blood losses, or gastrointestinal bleeding – exceed iron intake from food, tissues and iron stores become deficient.
This brings us to the question, does iron supplementation benefit physical performance in women of reproductive age?

Pasricha et al. performed a systematic review and meta-analysis – which was recently published in Journal of Nutrition – to address this question.
While, I’d love to tell you details about the meta-analysis – let’s cut it short and jump to the findings.
Women who were given an iron supplement showed improvements in maximal oxygen consumption. Additionally, daily iron supplementation enabled women to perform an exercise using a lower heart rate with greater efficiency. The improvements in maximal and submaximal exercise performance from daily oral iron supplementation were clearest in iron-deficient and trained women.
According the Pasricha et al., this is the first published meta-analysis providing evidence of beneficial effects of iron supplementation on physical performance.
Athletes should always remember to consult with a registered dietitian prior to taking any dietary supplement to assess any risks.

Gavin Van De Walle is an ISSA Certified Fitness Trainer, a NANBF Natural Competitive bodybuilder, a nutrition columnist for “The Collegian,” and a dietetic student at South Dakota State University. Once Gavin becomes an RD, he will aim to achieve the distinguished Certified Specialist in Sports Dietetics (CSSD) credential.

1.       S.-R. Pasricha, M. Low, J. Thompson, A. Farrell, L.-M. De-Regil. Iron Supplementation Benefits Physical Performance in Women of Reproductive Age: A Systematic Review and Meta-AnalysisJournal of Nutrition, 2014; DOI:10.3945/jn.113.189589