Gut microbiota composition refers to the specific types and proportions of microorganisms that comprise the community in the gut. The composition can vary from person to person, and it plays a crucial role in various physiological functions, including digestion, immune regulation, and even mental health.

Gut microbiota diversity refers to the variety of different microorganisms, including bacteria, viruses, fungi, and other microbes, present in the gastrointestinal tract. A diverse gut microbiota typically includes a wide range of microbial species, which is associated with better overall health.

The gut lumen is the hollow interior space inside the gastrointestinal tract (GIT), starting from the mouth and extending to the anus. It is the region of the GI tract where ingested food and liquids are mixed with digestive secretions and undergo chemical and mechanical digestion. The gut lumen is surrounded by the other parts of the intestinal wall: the mucosa, the submucosa, the muscularis, and the serosa. It is also home to diverse microbial species known as gut microbiota.

Gut peptides are small protein-like molecules released by the gut and are structurally composed of 36 amino acids. Gut peptides exert biological effects on various organs, including the brain and the gut. Examples include PYY, CCK, and GLP (Holzer et al., 2012).

Gut-associated lymphoid tissues are the gut’s largest mass of lymphoid tissues and immune cells (such as B and T-cells, neutrophils, mast cells, macrophages, and dendritic cells). GALT is critical in maintaining gut health and protecting it from potentially harmful pathogens (Ruth & Field, 2013