The Role of Polyphenols in Respiratory and Gut Health: From the Perspective of Gut-Lung Axis.

The gut-lung axis constitutes a dynamic, multidirectional communication platform between the gastrointestinal and respiratory tracts. Its complexity arises from the integrated crosstalk among the microbiota, immune system, and redox homeostasis, collectively influencing disease susceptibility and progression. The gut microbiota directly impacts pulmonary inflammation through immune modulation and oxidative stress regulation. Conversely, disturbances in lung homeostasis, including shifts in the local microbiota, can in turn reshape gut microbial communities, establishing a bidirectional feedback loop. Polyphenols, a class of bioactive compounds abundant in plant-based foods, have emerged as key modulators of this bidirectional network. The primary objective of this review is to systematically synthesize current knowledge on the mechanisms by which polyphenols orchestrate gut-lung axis. We critically examine how they modulate gut and lung microbiota, redox homeostasis, and immune responses, thereby impacting the progression of respiratory and gastrointestinal diseases. This review aims to highlights the translational significance of polyphenols as dietary components and therapeutic candidates, while identifying key knowledge gaps, such as dose optimization and combination strategies, to guide future research aimed at harnessing the gut-lung axis for disease prevention and treatment.