Chronic Adherence to a Ketogenic Diet Modifies Iron Metabolism in Elite Athletes

Purpose The short-term restriction of carbohydrate (CHO) can potentially influence iron regulation via modification of post-exercise interleukin-6 (IL-6) and hepcidin levels. This study examined the impact of a chronic ketogenic low CHO-high fat (LCHF) diet on iron status and iron-regulatory markers in elite athletes. Methods International-level race walkers (n=50) were allocated to one of three dietary interventions; i) a high CHO diet (HCHO; n=16), ii) periodized CHO availability (PCHO; n=17) or iii) a LCHF diet (n=17) while completing a periodized training program for 3 weeks. A 19-25 km race walking test protocol was completed at baseline and following adaptation, and changes in serum ferritin, IL-6 and hepcidin concentrations were measured. Results from HCHO and PCHO were combined into one group (CHO; n=33) for analysis. Results The decrease in serum ferritin across the intervention period was substantially greater in the CHO group (37%) compared to the LCHF (23%) group (p=0.021). After dietary intervention, the post-exercise increase in IL-6 was greater in LCHF (13.6-fold increase; 95% CI 7.1-21.4), than athletes adhering to a CHO-rich diet (7.6-fold increase; 5.5-10.2; p=0.033). While no significant differences occurred between diets, confidence intervals indicate 3 h post-exercise hepcidin concentrations were lower after dietary intervention compared to baseline in CHO (β=-4.3; -6.6, -2.0), with no differences evident in LCHF. Conclusion Athletes who adhered to a CHO-rich diet experienced favorable changes to the post-exercise IL-6 and hepcidin response, relative to the LCHF group. Lower serum ferritin after 3 weeks of additional dietary CHO might reflect a larger more adaptive hematological response to training. Address for correspondence: Prof David Pyne, Research Institute for Sport and Exercise, University of Canberra, Canberra, Australia, 2601. Email: david.pyne@canberra.edu.au This study was funded by a Program Grant from Australian Catholic University Research Fund, and a grant from the Australian Institute of Sport's High Performance Sport Research Fund. The authors declare no conflict of interest. The results of the present study do not constitute endorsement by the American College of Sports Medicine. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: October 2018. © 2018 American College of Sports Medicine

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