Acute Carbohydrate Consumption On The Iron-regulatory Response To Exercise In Elite Keto-adapted Endurance Athletes

Abstract

PURPOSE: To investigate the impact of CHO re-introduction in athletes previously adapted to a LCHF diet on subsequent inflammatory and hepcidin responses to exercise. METHODS: In the three weeks prior to the exercise trials, twenty-three elite race walkers adhered to either a CHO-rich (n=14) or LCHF diet (n=9). A 19-25 km race walking protocol was performed while the race walkers were still adhering to their allocated dietary intervention (Adapt). A second exercise test was performed three days later, where the LCHF consumed CHO 2 h prior to, and during the exercise protocol (in line with sports nutrition guidelines) for the first time in 3.5 weeks (CHO Restoration). Venous blood samples were collected pre-, post- and 3 h post-exercise and analysed for serum ferritin, interleukin-6 (IL-6) and hepcidin-25. RESULTS: Serum ferritin concentration was similar between trials (p=0.48) and dietary groups (p=0.93). The post-exercise IL-6 increase was greater in LCHF (p<0.001) during both Adapt (LCHF: 13.1-fold increase; CHO: 8.0-fold increase) and CHO Restoration (LCHF: 18.5-fold increase, CHO: 6.3-fold increase); outcomes were not different between trials (p=0.84). Hepcidin-25 levels increased 3 h post-exercise (p<0.001), however, they did not differ between trials (p=0.46) or diets (p=0.84). CONCLUSIONS: Strenuous exercise undertaken following chronic adaptation to a LCHF diet is associated with a greater post-exercise IL-6 response than when exercise is undertaken with high CHO availability. The elevated IL-6 response in athletes adapted to a LCHF diet is not attenuated by an acute increase in exogenous CHO availability. Despite diet-induced differences in IL-6 responses, no differences in hepcidin levels were evident, suggesting IL-6 is likely not the primary factor determining the magnitude of post-exercise hepcidin levels. Baseline iron status may be a more dominant factor regulating this response. Increased IL-6 levels may negatively influence other body processes, and the long-term impact of adhering to LCHF on other health outcomes warrants further investigation.