For elite athletes competing internationally, crossing multiple time zones may pose a physiological threat that extends well beyond fatigue. Circadian desynchronization doesn't just disrupt sleep — it may fundamentally alter the gut microbiome's rhythmic functions in ways that impair metabolism, inflammation control, and muscle recovery, raising questions about how training science addresses travel as a genuine performance variable.
This narrative review in Nutrients synthesizes evidence on what the authors term "gut jet lag" — a state in which rapid time-zone transitions disrupt the synchronized daily oscillations of both the central circadian clock and the gut microbiota. The loss of this synchrony is associated with reduced production of short-chain fatty acids (SCFAs) — specifically acetate, propionate, and butyrate — microbial metabolites that serve as direct energy substrates for skeletal muscle and modulate glucose uptake, lipid oxidation, and glycogen replenishment. Beyond metabolic disruption, circadian misalignment is linked to increased intestinal permeability and systemic inflammation, compounding impairments in sleep quality and cognitive performance. Travel-related stressors including dehydration, psychological stress, and dietary shifts toward processed foods were identified as further accelerants of dysbiosis and beneficial taxa depletion. The review proposes mitigation strategies including timed light exposure to reset the suprachiasmatic nucleus, chrono-nutritional meal timing to re-entrain peripheral clocks, and targeted synbiotic supplementation.
This review arrives at a moment of growing scientific interest in the gut-clock axis, a relatively nascent field that has rapidly expanded since foundational murine work by Thaiss et al. demonstrated diurnal microbial oscillations. What distinguishes this analysis is its application to a high-stakes practical context — the 2026 FIFA World Cup, where teams will navigate intercontinental travel schedules. However, the narrative review format limits causal inference; most underlying evidence derives from animal models or small human studies with heterogeneous methodologies. The proposed synbiotic interventions, while mechanistically plausible, lack robust randomized trial support in athlete populations specifically. Nonetheless, the synthesis represents a valuable conceptual framework, and the SCFA-muscle recovery pathway in particular warrants targeted human investigation. For sports medicine practitioners, this review signals that travel protocols may need to integrate microbiome-aware strategies alongside conventional chronobiological approaches.