Food & Nutrition Science

Top Key Gut Health Terminology 

Whether you are learning about gut health as part of a structured course or are learning more about gut health on your own, it can take time to look up key terminology.  

Here, we’ve pulled together the most important terminology related to gut health in an easy-to-read glossary. Throughout the blog below, you will find links where you can learn more about the topic, and at the end, you will find a comprehensive list of research articles to explore.  

Happy learning!

Gut Health (Biomedical Perspective) 

Gut health is defined by an absence of a set of biomarkers, namely gastrointestinal symptoms (e.g., abdominal pain, diarrhea), disease (e.g., inflammatory bowel disease, colon cancer), increased intestinal permeability, mucosal inflammation, and the deficiency (or even excess) of short-chain fatty acids.  

Gut Health (Wellness Perspective) 

Gut health is the active process through which people become aware of a more successful existence that benefits the gut and all health elements associated with it. 


Wellness is an active process through which people become aware of, and make choices toward, a more successful existence. 

Gastrointestinal Diseases 

Gastrointestinal diseases affect the gastrointestinal (GI) tract from the mouth to the anus. Some examples include nausea, heartburn (GERD), lactose intolerance, diarrhea, gallstones, irritable bowel syndrome (IBS), and Chron’s disease. Many gastrointestinal diseases have a component related to the gut microbiome.  

Functional Nutrition 

Functional nutrition is the practice of considering every aspect of health, diet, and overall lifestyle when giving nutrition recommendations. It aligns with the ideologies of functional medicine. Gut health and wellness are a cornerstone of functional nutrition.  


The microbiota comprises all living members forming the microbiome. Most of the microbiota are bacteria, but they also include fungi, helminths, and viruses.  


The microbiome is a community of bacteria, fungi, and viruses that live in and on the human body. The gut microbiome refers to the community of microbiota or microbes that live in the gut.  

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The way in which organisms live together for their mutual, and therefore, intrinsic benefit. In reference to the human body, symbiosis is a beneficial relationship between the host (the human body) and the microbes that inhabit in and on it. The gut microbiome is described as a “symbiotic relationship” between microbes and humans. There is symbiosis when there is a population of gut microbes that support health.    


Dysbiosis can be defined as a reduction in microbial diversity and a combination of the loss of beneficial microbes in the microbiome, either in number or type. It is called dysbacteriosis when it refers specifically to bacterial populations.  


Biofilms are aggregates of bacteria, fungi, and other microorganisms that live in communities. Biofilms are made up of starchy matrices that protect the microorganisms from the environment. Depending on whether they house pathogens or commensals and probiotics, they can be beneficial or harmful.    

Digestive System 

The organs that take in food and liquids and break them down into substances that the body can use for energy, growth, and tissue repair.  


The complex process of turning the food you eat into nutrients, which the body uses for energy, growth, and cell repair needed to survive. The digestion process also involves creating waste to be eliminated.  


Also called the cephalic phase, or simply “eating,” ingestion refers to the entry of food into the gastrointestinal tract. 

Epithelial Cells  

Epithelial cells are those lining the lumen of the stomach and small intestine.   


Pathogens are microbes that make us sick through infection.  


Pathobionts are members of the microbiota that exert specific effects on the host’s mucosal immune system associated with the development of clinical disease. They are low-virulence microbes.  

Commensals (Commensal Microbes) 

Commensals refer collectively to the normal bacteria in the gut. They enhance the digestion of macronutrients and synthesize short-chain fatty acids and vitamins. 


Also called probionts, probiotics are symbiotic bacteria that provide a benefit to the host by making vitamins and regulating immune function. Probiotics confer health benefits by the same mechanisms as your commensal bacteria. 


Prebiotics are food substrates that nourish and stimulate the growth of microbes that support human health while also reducing disease-causing bacteria. Prebiotic-rich foods feed the microbes, which in turn create multiple substrates, including short-chain fatty acids (SCFA). 


Supplements in which prebiotics and probiotics are found together.  


Psychobiotics are beneficial bacteria (probiotics) or support for such bacteria (prebiotics) that influence bacteria–brain relationships and have an impact on mental health. 


Postbiotics are bioactive compounds made when the gut microbiota digest and break down prebiotics. They are also referred to as microbial metabolites.  

Short-Chain Fatty Acids (SCFA)* 

*As they relate to gut health 

SCFAs provide fuel sources to the colon. 


Pharmaceuticals that eliminate pathogenic bacteria to treat infections. Often, antibiotics are not specific to pathogenic bacteria, so they can also eliminate commensal bacterial, changing the balance of intestinal microbes.    

Enteric Nervous System (ENS) 

The ENS, also referred to as the intrinsic nervous system, is one of the main divisions of the gastrointestinal tract. In fact, the enteric nervous system (ENS) is often referred to as the “second brain” because it is capable of acting independently of the sympathetic and parasympathetic nervous systems, although it may be influenced by them. 

Vagus Nerve 

The vagus nerve is the main nerve of your parasympathetic nervous system. This system controls specific body functions such as digestion, heart rate, and immune system. These functions are involuntary, meaning you can’t consciously control them. 

Gut-Brain Axis (GBA) 

The GBA is the pathway for bi-directional communication between the gut, via the enteric nervous system, and the brain, via the central nervous system.   

Microbiome-Gut-Brain-Axis (MGB Axis) 

The role of the microbiome in modulating gut-brain signaling has become more apparent in recent years, giving rise to the concept of a microbiota-gut-brain axis (MGB axis).  The MGB axis is the pathway for bi-directional communication between the microbiome, the gut, and the central nervous system.  

Hypothalamus-Pituitary Axis (HPA Axis) 

The hypothalamus-pituitary axis (HPA axis) is one of the most important components of the MGB axis. It provides a primary biological response to stressful stimuli. The gut microbiota plays an important role in shaping brain functions and behavior, including the activity of the HPA axis. 

Increased Intestinal Permeability 

The intestines are semi-permeable. The mucosal layer absorbs water and nutrients from the food, as well as metabolites and other chemicals from gut microbiota. However, some people have an impaired mucosal barrier function as a result of inflammation or infection, initiating factors that lead to increased permeability. With chronic inflammation, there are persistent changes in the mucosal barrier function, and it opens the door to the development of diseases that affect the GI tract and the entire body.  Sometimes, it is called “leaky gut syndrome.”  

Bacterial Translocation 

Bacterial translocation is defined as the passage of viable bacteria from the gastrointestinal (GI) tract to extraintestinal sites 

Inflammation and Chronic Inflammation 

Inflammation is the immune system’s natural response to an irritant. If the immune system is successful at protecting and healing the area, inflammation will go down, and the area will no longer hurt. However, in some cases, inflammation is not helpful to the body. Some conditions, called autoimmune diseases or chronic inflammatory diseases, attack the body’s cells by mistake. This causes inflammation that is harmful to the body. 


Cytokines are small proteins that are crucial in controlling the growth and activity of other immune system cells and blood cells. Inflammatory cytokines, or pro-inflammatory cytokines, are markers of inflammation.  


Antinutrients are components found in food that affect the body’s ability to absorb nutrients or convert those nutrients into substances the body can use. They are naturally found in plant foods, especially grains, pulses, and legumes, but also leafy vegetables. 

Therapeutic Diet 

A therapeutic diet is a meal plan that controls the intake of certain foods or nutrients. It is part of the treatment of a medical or nutritional condition.

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