The Quiet Conversation between Two Brains: Exploring Gut-Brain Axis: From Classical Unani

The gut?brain axis (GBA) is a bidirectional communication system connecting the gastrointestinal tract and the brain through neural, neuroendocrine, immune and metabolic pathways. Modern research has highlighted the role of the enteric nervous system, vagus nerve, autonomic nervous system, enteroendocrine signalling, intestinal barrier and gut microbiota in this communication. The relationship between gastrointestinal function and the brain is also described in classical Unani literature. Ibn al-Quff, in Kitab al-Umda fi al-Jarahat, described neural relationships involving the gastrointestinal organs, while Ibn Rushd, in Kitab al-Kulliyat, discussed the influence of gastrointestinal disturbances on the brain in relation to Mizaj, Nafs-e-Dimagh and A'saab. Allama Kabeeruddin, in Al-Akseer, described the stomach as an organ capable of producing distress in the brain and discussed conditions such as Suda' and Sara'. Akbar Arzani, in Tibb-e-Akbar, also described headaches associated with gastric dysfunction, abnormal temperament and morbid matter. These classical descriptions provide a historical perspective on the relationship between gastrointestinal and neurological functions. Contemporary research has identified several mechanisms that may contribute to gut?brain communication, including vagal signalling, microbial metabolites, intestinal barrier function, immune activation and neuroendocrine pathways. Some of these mechanisms provide areas for comparison with observations described in classical Unani literature. However, concepts such as Bukharat, Akhlat, Sawda and Kayl?s should not be considered direct equivalents of modern microbial metabolites, immune mechanisms or neuroendocrine pathways. Instead, they can be examined as historical physiological concepts that may provide a basis for generating research questions. This review discusses the gut?brain relationship from both contemporary biomedical and classical Unani perspectives, while maintaining a distinction between historical descriptions and experimentally established mechanisms.