Sufficient iron availability is necessary to support the work involved in strenuous exercise by trained athletes. However, this population tends to exhibit lower iron status, with the rates being higher among females than males. The levels of IL-6 are known to increase after an exercise bout along with an increase in circulating hepcidin concentrations between 3 and 6 hours after exercise. Although hepcidin decreases iron absorption, no work has been done to determine iron absorption during the period of elevated hepcidin concentrations. Barney and colleagues conducted a study to explore this issue and report their results in the September 2022 issue of The Journal of Nutrition.
Male and female cross country runners (n = 28; serum ferritin = 21.9 ng/mL) consumed a stable iron isotope with a standard meal 2 hours after a prolonged run and blood was collected 1 hour later. Two weeks later the same protocol was used to collect samples, however, the subjects were in a state of rest at the time of meal consumption. Isotope enrichment in red blood cells was determined 15 days after the exercise and rest periods.
Exercise led to a 51% increase in hepcidin and fractional iron absorption was reduced by 36%, compared to the rest period. Exercise also led to an increase in IL-6 concentrations in plasma. Although sample numbers were limiting, the response may be occurring in males, but not females. These observations led the authors to conclude that prolonged exercise increases hepcidin and decreases iron absorption in trained athletes with low iron stores. They suggest further work is needed to determine if there are sex differences in the hepcidin response.
In an editorial, Peeling indicates the work by Barney and colleagues have advanced our understanding of the potential mechanisms underlying iron deficiency in athletes. Peeling suggests that knowing the timeline of transient increases in hepcidin and decreases in iron absorption relative to an exercise bout should facilitate the planning of meals with higher iron content.
References
David E Barney, Jr, James R Ippolito, Claire E Berryman, Stephen R Hennigar, A Prolonged Bout of Running Increases Hepcidin and Decreases Dietary Iron Absorption in Trained Female and Male Runners, The Journal of Nutrition, Volume 152, Issue 9, September 2022, Pages 2039–2047, https://doi.org/10.1093/jn/nxac129.
Peter Peeling, Towards an Understanding of the Acute Impacts of Exercise on Iron Absorption in Athletes, The Journal of Nutrition, Volume 152, Issue 9, September 2022, Pages 2013–2014, https://doi.org/10.1093/jn/nxac149.
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