The gut microbiome has emerged as a pivotal area of research due to its significant influence on the immune system and cognitive functions. Cognitive disorders, including dementia and Parkinson’s disease, represent substantial global health challenges. This review explores the relationship between gut microbiota, immune modulation, and cognitive decline, with a particular focus on the gut-brain axis. Research indicates that gut bacteria produce metabolites, including short-chain fatty acids (SCFAs), which affect mucosal immunity, antigen presentation, and immune responses, thereby influencing cognitive functions. A noteworthy correlation has been identified between imbalances in the gut microbiome and cognitive impairments, suggesting novel pathways for the treatment of cognitive disorders. Additionally, factors such as diet, environment, and pharmaceuticals play a role in shaping the composition of the gut microbiome, subsequently impacting both immune and cognitive health. This article aims to clarify the complex interactions among gut microbiota, immune regulation, and cognitive disorders, evaluating their potential as therapeutic targets. The goal is to promote microbiome-based treatments and lay the groundwork for future research in this field.

The global rise in obesity rates has prompted a thorough evaluation of dietary strategies that may alleviate this metabolic issue. Fermented tea, a beverage rich in polyphenols and catechins, has emerged as a viable therapeutic option for obesity management. This review discusses the role of fermented tea in modulating the gut microbiome, a critical factor in energy regulation and obesity. We explore how the bioactive components in fermented tea influence gut health and their implications for metabolic health. Fermented tea may inhibit weight gain and fat accumulation in obese animal models, likely by promoting beneficial bacteria and suppressing harmful species. Changes in the production of short-chain fatty acids and improvements in gut barrier integrity are linked to enhanced insulin sensitivity and reduced inflammatory markers, essential for effective obesity management. However, barriers remain in applying these findings in clinical settings, such as the need for standardized fermentation techniques and accurate dosage assessments. This review underscores the therapeutic potential of fermented tea in obesity treatment and advocates for further research to enhance its integration with public health initiatives.

The interplay among diabetes, cognitive decline, and the gut microbiome represents an emerging field of scientific inquiry. The gut‐brain axis serves as a crucial communication network between the gastrointestinal system and the central nervous system, playing a significant role in diabetes‐related cognitive deterioration. Fermented tea, enriched with bioactive constituents, offers a promising therapeutic strategy by modulating this axis. Specifically, compounds including catechins in fermented tea positively modulate gut microbiota composition, promoting commensal bacteria while suppressing pathogenic strains. This microbial shift enhances the production of short‐chain fatty acids, which may strengthen gut barrier integrity, attenuate systemic inflammation, and thereby influence cognitive health via the gut‐brain axis. Concurrently, the antioxidant properties of tea polyphenols and catechins mitigate oxidative stress, a key pathogenic factor in diabetic cognitive impairment. Furthermore, the anti‐inflammatory effects of fermented tea may potentially ameliorate chronic low‐grade inflammation in diabetes, offering a plausible pathway for cognitive improvement. This systematic review, conducted through comprehensive searches of PubMed, Web of Science, CNKI (China National Knowledge Infrastructure), and Wanfang databases, synthesizes evidence supporting fermented tea as a natural intervention to preserve cognitive function in diabetic individuals by targeting the gut microbiome and the gut‐brain axis. Notably, it also explores the potential application of Chibi Green Brick tea as a regionally specific intervention for diabetes‐related cognitive dysfunction. Collectively, these insights underscore the necessity for rigorous mechanistic investigations and robust clinical validation to fully elucidate therapeutic mechanisms of fermented tea and translate these findings into clinical practice.