The Interplay Between Redox Status, Exercise Intensity, and Mucosal Immunity: Toward Context-Dependent Antioxidant...

Exercise simultaneously challenges redox homeostasis, neuroendocrine regulation, metabolism, and immune function. The response is strongly dependent on exercise dose, recovery, nutritional status, and individual characteristics. This perspective updates the evidence on the relationship among exercise intensity, redox biology, and mucosal immunity, with particular emphasis on salivary secretory immunoglobulin A (sIgA) and antioxidant strategies. Current evidence supports a hormetic interpretation: exercise-derived reactive oxygen and nitrogen species (ROS/RNS) are not intrinsically harmful and participate in adaptive signaling, whereas excessive or poorly recovered exposure can contribute to oxidative damage, inflammation, impaired recovery, and transient changes in immune function. A 2024 randomized crossover study in 12 untrained young men found that the 75% VO₂max condition produced a significantly lower percentage change in sIgA secretion rate compared with the 55% VO₂max condition, while lower-intensity or shorter-duration trials did not. Importantly, this finding should be interpreted as a protocol-specific observation rather than evidence of a universal biological threshold. Salivary oxidative-stress evidence is also heterogeneous, and the quality of evidence remains low. Contemporary antioxidant guidance increasingly favors food-first approaches and selective supplementation for nutrient inadequacy or periods of unusually high training stress rather than routine high-dose antioxidant use. Evidence for specific interventions is mixed: astaxanthin, β-glucans, sesame, and polyphenol formulations show promising but still limited human evidence, while a 2024 trial in adults with obesity illustrates that melatonin, a pleiotropic redox-modulating molecule, can produce context-dependent effects. The most defensible personalized framework therefore combines training load, recovery, dietary adequacy, mucosal-immune monitoring, and-where clinically justified-redox phenotyping. Genetic and multi-omics approaches remain research tools rather than established clinical decision rules.