Mental health is a state of emotional, psychological, and social well-being that influences our thoughts, feelings, and behaviors (Manwell et al., 2015).

Mental illness is a health problem that impairs a person’s cognition, emotions, and behavior, such as depression, anxiety, schizophrenia, etc. (Malla et al., 2015).

Metabolic psychiatry explores the connections between metabolic factors—such as glucose metabolism, insulin resistance, and inflammation—and mental health. It examines how these factors can influence the development and progression of psychiatric disorders, and it investigates their potential role in both the onset and treatment of conditions like depression, anxiety, and other mental health challenges.

Metabolism refers to the set of biochemical processes that occur within an organism to sustain life. It involves the conversion of nutrients from food into energy and the synthesis and breakdown of molecules necessary for cellular function.

Metabolites are the by-products of chemical reactions within cells that are stimulated by different enzymes and used in different metabolic processes. For example, the breakdown of food produces byproducts such as fat, glucose, or amino acids, which are required for growth, development, and reproduction.

Metabolomics is the study of the complete set of metabolites in a biological system, such as cells, tissues, or organisms. It involves analyzing small molecules involved in metabolic processes to understand disease mechanisms, health conditions, and the impact of diet and lifestyle.

Methylation is a biochemical process involving adding a methyl group (one carbon atom and three hydrogen atoms) to specific molecules, such as DNA, proteins, and neurotransmitters. This process regulates gene expression, cellular functions, and various metabolic pathways.

MGBA communication carriers consist of gut peptides, neuroactive chemicals, hormones, and signaling molecules released by various organs interlinked with the MGBA mechanism and participate in both top-down and bottom-up communication mechanisms.

‘Cross-talk’ refers to the bi-directional communication between the gut, its microbiome, and the brain through intricate neuro-immuno-endocrine communication pathways. MGBA cross-talk facilitates many functions, such as digestion, stress regulation, immune system modulation, and cognitive processes.

Microbial diversity measures the variety of species in the gut microbiota. Higher diversity indicates a healthy microbiota because it contains a diverse range of species, each performing a different beneficial function for the host.