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Gastrointestinal Tract 101


What is the gut barrier, how does it impact your health, and what can you do to protect it?


Your gastrointestinal (GI) tract contains many connected organs across a long, twisting tube that starts at your mouth and ends at your rectum. The hollow organs that make up the GI tract are your mouth, esophagus, stomach, small intestine, large intestine, and anus. The GI tract is part of the digestive system that also includes solid organs such as your liver, pancreas, and gallbladder. 


The primary role of the GI tract is to enable the passage of the food you eat to your stomach, to control the breakdown of that food, to facilitate the digestion and absorption of the nutrients in the food, and then to excrete all things considered waste. 


The gut barrier: why is it so important?

Although your gut is designed to facilitate food processing and the separation of important nutrients from wasteful products, its role extends much further than that. Your gut barrier, or gut lining, arguably may be the most important organ in your body.


Your gut lining protects you from pathogens entering your system, helps maintain a healthy relationship between your body and the microorganisms that reside in your intestines, and coordinates your immune response.1,2


These functions are performed across your gut barrier, a multi-layer functional unit of your gut that has two main components: a physical barrier and a deep, functional barrier. The physical barrier is mainly composed of a large community of microorganisms (bacteria, viruses, fungi) otherwise known as the microbiota. The functional barrier consists of the innate and adaptive immune cells that form the gut-associated lymphoid tissue, which is responsible for immune response.


The gut barrier: how does it impact your health?

Both the physical barrier and the functional barrier are maintained and modulated by intestinal microorganisms and host immune cells. These cells are responsible for protecting your gut barrier, controlling inflammation, and preserving gut homeostasis.3


For example, short-chain fatty acids (SCFA) are gut microbial metabolites that are typically produced during the digestion of dietary fibers. SCFAs are used to produce energy and balance your gut-brain axis.4  SCFAs also contribute to immune regulation by enhancing mucus production and promoting the development of regulatory T cells (your body’s fundamental immune response cells). 


Your gut barrier can become compromised with acute stress – such as heat, intense exercise, psychological stress, and antibiotic use – or chronic stress such as occurs with chronic autoimmune conditions and GI, neurological, and metabolic diseases. A compromised gut barrier can manifest as an alteration in the gut microbiota (dysbiosis) and damage to the gut epithelial layer. In turn, subsequent damage to the gut barrier can result in the leakage of harmful microorganisms from the GI tract into the bloodstream, which can further compromise immune response or complicate metabolic disorders such as obesity or diabetes.5


Protecting the physical barrier and deep functional barrier is fundamental to your health, not only for increased energy and nutrient utilization but also to ensure foreign substances and inflammation do not compromise your health or your immune responses.6


The gut barrier: what can you do to protect it?

There are several ways you can protect the integrity of your gut barrier. Specific diet7 and nutritional supplements (probiotics/prebiotics/synbiotics)8 can help, but so can consistent moderate exercise,9 stress management,10 avoiding excessive or unnecessary antibiotic use,11 and regular gut testing.12


If these interventions seem very general, it’s because they are. Every individual should have an individualized plan of care for achieving and maintaining good gut health.


Onegevity’s GutBio at-home test provides a comprehensive gut health assessment so you can understand your gut health status today. Although it doesn’t measure direct gut barrier cell health, the insights from GutBio’s in-depth report identifies and measures the microorganisms associated with risks of having inflammation, constipation, and diarrhea. Each GutBio report provides personalized and actionable diet, supplementation, and lifestyle recommendations based on your bacteria counts and ratios that will help you optimize your gut community and maintain gut health, nutrient absorption and utilization, and immune health.


1.     Viggiano D, Ianiro G, Vanella G, et al. Gut barrier in health and disease: Focus on childhood. Eur Rev Med Pharmacol Sci 2015;19(6):1077-1085.

2.     Turner J. Intestinal mucosal barrier function in health and disease. Nat Rev Immunol 2009. doi:10.1038/nri2653

3.     Okumura R, Takeda K. Maintenance of intestinal homeostasis by mucosal barriers. Inflamm Regen 2018;38(1):5. doi:10.1186/s41232-018-0063-z

4.     Dalile B, Van Oudenhove L, Vervliet B, Verbeke K. The role of short-chain fatty acids in microbiota–gut-brain communication. Nat Rev Gastroenterol Hepatol May 2019:1. doi:10.1038/s41575-019-0157-3

5.     Chelakkot C, Ghim J, Ryu S. Mechanisms regulating intestinal barrier integrity and its pathological implications. Exp Mol Med 2018;50(8):103. doi:10.1038/s12276-018-0126-x

6.     Vancamelbeke M, Vermeire S. The intestinal barrier: a fundamental role in health and disease. Expert Rev Gastroenterol Hepatol 2017;11(9):821-834. doi:10.1080/17474124.2017.1343143

7.     De Santis S, Cavalcanti E, Mastronardi M, et al. Nutritional keys for intestinal barrier modulation. Front Immunol 2015;6:612. doi:10.3389/fimmu.2015.00612

8.     Schrezenmeir J, de Vrese M. Probiotics, prebiotics, and synbiotics – approaching a definition. Am J Clin Nutr 2001;73(2):361s-364s. doi:10.1093/ajcn/73.2.361s

9.     Monda V, Villano I, Messina A, et al. Exercise modifies the gut microbiota with positive health effects. Oxid Med Cell Longev 2017;2017:3831972. doi:10.1155/2017/3831972

10.     Mayer E. The neurobiology of stress and gastrointestinal disease. Gut 2000;47(6):861-869. doi:10.1136/gut.47.6.861

11.     Spiller R. Hidden dangers of antibiotic use: increased gut permeability mediated by increased pancreatic proteases reaching the colon. Cell Mol Gastroenterol Hepatol 2018;6(3):347-348.e1. doi:10.1016/j.jcmgh.2018.06.005

12.     Bischoff S. Gut health: a new objective in medicine? BMC Med 2011;9:24. doi:10.1186/1741-7015-9-24