Caffeine Modifies the Immune and Anti-inflammatory Responses to Short Incremental Cycling Exercise Until Exhaustion in Humans: A Pilot Study

Exercise has well-documented effects on immune function with both positive and negative sequelae dependent on intensity, volume, and duration. The immunosuppressive effects of exercise are mediated, in part, by the complex interaction of cytokines, catecholamines, and nutrition. Caffeine has been reported to modulate immune function; however, the interaction with brief exhaustive exercise is not well characterized. It was hypothesized that caffeine would upregulate the cytokine response to intense exercise. Seven male students volunteered to participate in a randomized, double-blinded crossover study where they ingested either caffeine (6 mg/kg) or a maltodextrin placebo (6 mg/kg) 1 h prior to a cycling exercise. The exercise protocol started at 100 W and the intensity was increased by 50 W every two minutes until exhaustion. Serum samples were collected pre-, post-, and 1-h post-exercise and analyzed for IL-4, IL-10, and TGF-β1. Caffeine ingestion increased time to exhaustion (P = 0.005; Effect Size [ES] = 1.33), IL-4 (P = 0.004; ES = 2.34), IL-10 (P = 0.047; ES = 0.41 ± 0.57), and TGF-β1 (P = 0.013; ES = 0.76). The accentuated response of the cytokines may have important ramifications due to their potent anti-inflammatory and immunoregulatory properties. Specifically, the 6 mg/kg caffeine dose not only improved exercise performance but the cytokine data is indicative of an upregulated inflammatory response and an enhancement of the anti-inflammatory benefits of exercise.