Do microbiota rhythms influence cognitive performance? - A narrative review

The gut microbiota exhibits diurnal oscillations that are increasingly recognized as important modulators of host physiology, including brain function. Increasing evidence suggests that diurnal oscillations in microbial composition and activity may play a role in shaping cognitive performance. Microbiota and host circadian systems are tightly interconnected through feeding-fasting cycles, light-driven central clock signaling, and peripheral metabolic regulation, leading to coordinated rhythmicity across physiological systems. Disruptions to these rhythms, such as irregular eating patterns or circadian misalignment, have been associated with alterations in microbial profiles and impaired cognitive outcomes. Microbiota-derived metabolites, including short-chain fatty acids, tryptophan metabolites, and bile acids, serve as key signaling molecules that mediate communication along the gut-brain axis and influence processes such as memory, attention, and executive function. Emerging data support the existence of an integrated microbiota-circadian-cognition axis, in which microbial rhythmicity contributes to the regulation of neural and behavioral functions. Although current findings point to a meaningful association between microbiota rhythms and cognitive function, the evidence remains largely indirect and heterogeneous, showing that the time-related links between the microbiota and the brain are complex and not easy to explain. The aim of this narrative review is to synthesize current evidence on the relationships between microbiota rhythmicity, circadian regulation, and cognitive function, with a focus on possible mechanisms and potential clinical applications.