Six Days of Low Carbohydrate, Not Energy Availability, Alters the Iron and Immune Response to Exercise in Elite Athletes

Oct 25, 2021Medicine and science in sports and exercise

Six Days of Low Carbohydrate Intake, Not Low Energy, Changes Iron and Immune Responses to Exercise in Elite Athletes

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Abstract

The low carbohydrate high fat diet led to significant increases in immune and inflammatory markers after exercise in elite race walkers.

Athletes on a low carbohydrate high fat (LCHF) diet showed greater increases in interleukin-6 and hepcidin levels following exercise compared to baseline measurements.
Postexercise total white blood cell counts and cortisol levels were also significantly elevated in LCHF athletes compared to their baseline levels.
Blood glucose concentrations decreased significantly after exercise in athletes following the LCHF diet, while no changes were observed in those on a high carbohydrate/energy availability diet or low energy availability diet.
No significant differences in any biological markers were found between the high carbohydrate diet and low energy availability diet groups.

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PURPOSE: To quantify the effects of a short-term (6-d) low carbohydrate (CHO) high fat (LCHF), and low energy availability (LEA) diet on immune, inflammatory, and iron-regulatory responses to exercise in endurance athletes.

METHODS: Twenty-eight elite male race walkers completed two 6-d diet/training phases. During phase 1 (Baseline), all athletes consumed a high CHO/energy availability (CON) diet (65% CHO and ~40 kcal·kg-1 fat-free mass (FFM)·d-1). In phase 2 (Adaptation), athletes were allocated to either a CON (n = 10), LCHF (n = 8; <50 g·d-1 CHO and ~40 kcal·kg-1·FFM-1·d-1), or LEA diet (n = 10; 60% CHO and 15 kcal·kg-1·FFM-1·d-1). At the end of each phase, athletes completed a 25-km race walk protocol at ~75% V˙O2max. On each occasion, venous blood was collected before and after exercise for interleukin-6, hepcidin, cortisol, and glucose concentrations, as well as white blood cell counts.

RESULTS: The LCHF athletes displayed a greater IL-6 (P = 0.019) and hepcidin (P = 0.011) response to exercise after Adaptation, compared with Baseline. Similarly, postexercise increases in total white blood cell counts (P = 0.026) and cortisol levels (P < 0.001) were larger compared with Baseline after LCHF Adaptation. Decreases in blood glucose concentrations were evident postexercise during Adaptation in LCHF (P = 0.049), whereas no change occurred in CON or LEA (P > 0.05). No differences between CON and LEA were evident for any of the measured biological markers (all P > 0.05).

CONCLUSIONS: Short-term adherence to a LCHF diet elicited small yet unfavorable iron, immune, and stress responses to exercise. In contrast, no substantial alterations to athlete health were observed when athletes restricted energy availability compared with athletes with adequate energy availability. Therefore, short-term restriction of CHO, rather than energy, may have greater negative impacts on athlete health.

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Six Days of Low Carbohydrate, Not Energy Availability, Alters the Iron and Immune Response to Exercise in Elite Athletes

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