GABA is an inhibitory neurotransmitter that regulates brain activity by reducing neuronal excitability. It counterbalances the effects of excitatory neurotransmitters, contributing to the overall balance of neural signaling. GABA is known for its calming effects and is implicated in conditions like anxiety and epilepsy.

The gastrointestinal tract (GIT), also known as the gut, digestive tract, or alimentary canal, is a long, twisted hollow tube that extends from the mouth to the anus and is made up of interconnected hollow organs, including the mouth, esophagus, stomach, small intestine, large intestine, and anus (Greenwood-Van Meerveld et al., 2017).

The GBA-microbiota crosstalk is a bidirectional communication system between the gut, microbiota, and brain. This communication occurs physically or biochemically and interlinks the gut with the cognitive and emotional centers of the brain, thus ensuring adequate mental health and intestinal homeostasis (Mayer, Tillisch, & Gupta, 2015).

Genes are the instruction manuals of living organisms made up of intricate DNA sequences; their function is to direct the production of specific proteins and enzymes required for survival.

The germ-free (GF) animal model refers to the study of animals raised in a sterile environment free of microorganisms (i.e., beneficial and pathogenic microbes) for research purposes (Bhattarai & Kashyap, 2016).

Ghrelin is often referred to as the “hunger hormone.” It is produced by the stomach and stimulates appetite, signaling to the brain that it’s time to eat (Pradhan et al., 2013).

A gland is a group of cells whose function is to produce and secrete a specific substance (such as hormones, digestive juices, tears, saliva, and milk) either directly into the bloodstream (in the case of endocrine glands) or through a duct or other opening inside or outside the body (in the case of exocrine glands) (Maynard & Downes, 2019).

Glucagon-like peptide -1 is a hormone the gut cells produces in response to food intake. GLP-1 reduces food intake and increases insulin secretion (Gribble & Reimann, 2016).

Glycans are sugar molecules with proteins and lipids in their chemical structure.

The Glycemic Index (GI) is a scale that measures how quickly a carbohydrate-containing food raises blood glucose levels compared to a reference food, reflecting its impact on post-meal blood sugar response.