Gut–brain axis, mental health, and Unani diet therapy (Ilaj-Bil-Ghiza): A narrative review

Abstract

The gut–brain axis (GBA) represents a bidirectional communication system linking the gut microbiota, enteric and central nervous systems, and neuroendocrine and immune pathways. Emerging evidence indicates that alterations in gut microbiota influence neurotransmission, neuroinflammation, and mood regulation. Unani medicine emphasizes ‘Ilaj bi’l-Ghiza (Diet therapy) as the primary mode of treatment and attributes mental health to balanced digestion, liver function, and mizāj (temperament). To integrate modern understanding of the GBA and mental health with Unani diet therapeutic principles, highlighting convergences and potential research directions. A narrative review was conducted using PubMed, ScienceDirect, and Unani classical sources. Literature on gut microbiota, diet, mental health, and Unani Diet therapy was analyzed and conceptually mapped to modern physiological mechanisms. Modern evidence demonstrates that microbial metabolites such as short-chain fatty acids and tryptophan derivatives modulate neurochemical and inflammatory pathways, influencing mood and cognition. Unani literature emphasizes the importance of digestive and hepatic health in maintaining Quwwat Ḥāfiẓa (the memory faculty) and Sukūn-e-nafs (mental tranquillity). Traditional diet therapeutic regimens, such as dahi, laban (fermented foods), Sikanjabīn (oxymel), Ma’ al-Jubn (whey), Ābkāma and Murabbā (preserved fruits), aim to balance (humours) Akhlāṭ and enhance both digestive and cognitive function. Integration of these perspectives suggests that Unani Diet therapy may beneficially modulate the GBA. The convergence between Unani dietary principles and modern gut–brain science offers a promising foundation for culturally relevant interventions in mental health. Future clinical studies integrating Unani diet therapy with microbiome and neurophysiological assessments could pioneer holistic, evidence-based approaches to mental well-being.