Mechanistic and hormetic insights into the interaction between dietary bioactive compounds and gut microbiota in modulating human health

• The gut microbiota is a complex ecosystem and is crucial for human health. • Dietary bioactive compounds promote the growth of beneficial bacteria. • Bioactive compounds alleviate dysbiosis and causes health benefits. The gut microbiota, a complex ecosystem of microorganisms, plays a pivotal role in maintaining host physiology and preventing disease. Emerging evidence indicates that specific dietary bioactive compounds can modulate gut microbial composition and function, thereby influencing systemic metabolic, immune, and neurological health outcomes. This review focuses on major classes of bioactive substances—carotenoids, phenolics, and terpenoids—and critically examines their interactions with the gut microbiota. Unlike previous reviews that broadly address diet–microbiota relationships, this work adopts a compound-specific and mechanistic approach, linking individual bioactives to microbiota-driven physiological pathways that collectively contribute to the prevention and management of chronic diseases such as obesity, diabetes, and cardiovascular disorders. Notably, many of these bioactive–microbiota interactions exhibit hormetic dose–response behavior, wherein moderate exposures activate adaptive cellular defense mechanisms, while excessive intake may induce metabolic stress. By integrating mechanistic and hormetic perspectives, this review provides novel insights for the development of plant-based therapeutic interventions and functional foods. The innovative framework presented here distinguishes this work from existing reviews and advances the field toward evidence-based, microbiome-centered nutrition and disease prevention strategies.