gut microbiota in health and disease

Role of the Gut Microbiota in Health and Disease

There are hundred times more microbial cells than human genes in our body. The gut microbiota, with the highest density of microbial cells in our organism, shows to have a huge impact in our health. In this post, we talk and discuss the role of gut microbiota in health and disease.

What's the gut microbiota? How is developed and shaped? How does the gut microbiota affect our health?

The answer of these and more, on this article! Go and scroll down!

What’s the Gut Microbiota?

The gut microbiota, also known as gut microbiome, is the community of microorganisms inhabiting your digestive tract (source). These microorganisms have established, through evolution, a symbiotic relationship with the host (humans). This is, both the host (human), and parasite (microorganism), benefit from each other (study)

The gut microbiota plays a big role in health and disease (study). From mouth to colon, there are microorganisms all around our digestive system. But it's in the colon where we are more interested in.

With the highest density of microbial cells (1012  cells/g), the gut microbiota in the colon has a lot to say about your health status. Metabolizing compounds, improving your inmune system, or even regulating your brain function (study)

But before getting into the role of microbiota in health and disease, let's talk more about how these microorganisms got into our gut.

gut microbiota

The Symbiotic Theory of the Gut Microbiota

The gut microbiota maintains a symbiotic relation with humans (study). They provide benefits to our metabolism, and in return they have a place to live and survive. But how did the microorganisms first get into our gut?

Microorganisms have been alive for much longer than humans. They are present everywhere. From the most remote places you can think of (vulcanos, north pole,...), to the most routinary and casual places (your desk, floor, lamp, car,...)

Microorganisms are also present in foods, water, and very close to us. Although all interactions with the environment could trigger the first microorganisms to enter our gut, it seems like the ingestion of foods containing microrganisms is what marked the "conquest" of our digestive tract. 

gut microbiota

The repeated ingestion of food and water containing microorganisms and our interaction with the environment established our gut microbiota. From there, part of the gut microbiota was vertically transferred generation by generation (study).

The gut microbiota was formed one, and it's now here to stay with us (forever). However, each of us shows a different gut microbiota composition, which makes it part of our identity as humans (study)

Gut Microbiota Development

The composition of the gut microbiota is part of our identity. Each one of use has a unique composition of microbial communities (study).

The gut microbiota largely depends on your lifestyle, diet, physical activity, use of antibiotics... and more factors of your every day life (study)

But here the question arises: How is the gut microbiota developed? If everyone has a different microbiota, how is it that we are able to shape and develop these microorganisms?

Factors Modulating Gut Microbiota

The gut microbiota is developed during the first years of life. The very start point is, in fact, the mode of delivery. Caesarean born children have a more slowly diversifying microbiota (study). The balance between Bifidobacterium and Clostridium species was also affected by the mode of delivery. This ratio is, in fact, a good marker of a healthy microbiota.

After 6 years of life, the gut microbiota is almost fully established. From there, the composition of the gut microbiota can be disturbed, but changes won't be ultimately permanent. 

Role of the Gut Microbiota in Health and Disease

The gut microbiota plays an important role in our health. It's considered by many an"essential organ", and we wouldn't be able to survive without it.

From metabolizing compounds, favouring digestions, providing inmunity, improving the function of the central nervous system.... In the next 5min, the role of the gut microbiota is health and disease

The Gut Microbiota Acts as a Defense Barrier

The intestinal barrier is our first defense against pathogens (study). The gut microbiota is, thus, the army ready to attack and stop any pathogen willing to infect us.

The microorganisms forming the gut microbbiota sit along the mucosa of the intestinal barrier (study). When pathogens come and the risk of infection is high, the gut microbiota secretes antimicrobial compounds that kill the pathogens (study). This is a mechanism of auto-defense that can largely favour our inmunity towards microbial infections.

Gut microbiota and intestial barrier

Dysbiosis of the gut microbiota, can, on the same way, affect the function of the intestinal barrier (study). Harmful bacteria in your intestine release enterotoxins, increasing the permeability of the intestine.

In other words, what wasn't able to pass through the intesinal barrier now is. This means a higher risk of microbial infection, and increased inflammation to fight the pathogens entering our system.

The Gut Microbiota Modulates the Inmune System

The microbiota plays a big role on the induction, training and function of the host immune system (study). There's a direct connection between the inmune system of the host and the gut microbiota.

The symbiotic relationship established between both the microorganisms and humans means that our inmune system has been able to adapt to the presence of the gut microbiota. Instead of activating the inmune response and trying to fight it, our inmune system is satisfied with the gut microbiota, and doesn't trigger any inmune response

Gut Microbiota and Inmunity

The gut microbiota trains our inmune system. By identifying the gut microbiota at a molecular level, our inmune system is able to distinguish between "own" and "foreign" microorganism.

The presence of pathogens and production of their metabolites active the inmune system. By means of T-cells, Dendritic cells, or macrophages, the cascade of inmune response is triggered.

Metabolic Functions of the Gut Microbiota

The main and most important role of the gut microbiota; metabolization of compounds we are not able to metabolize.

The gut microbiota is integral to host digestion and nutrition (study). It can synthesize nutrients from substrate we are not able to break down and metabolize. These include xyloglycans, non-digestible fibre. In fact, everything that is not readily digested in the upper digestive tract could be a potential substrate for the gut microbiota (study).

Gut microbiota and SCFAs

The gut microbiota uses this substrate to stay alive, grow, and produce benefitial compounds for the host. For instance, the metabolization of dietary fibres by the gut microbiota produces Short-Chain-Fatty-Acids (SCFAs) (study). These compounds can help you regulate hunger and appetite, improve energy metabolism, and regulate inflammation (study)

Gut Microbiota and the Gut-Brain Axis

There's a lot more to know in relation to the gut-brain axis and the role the gut microbiota plays here, but one thing is clear: a healthy gut microbiota can improve your brain function and neuro-endocrine systems (study)

The gut and the brain are in direct contact. The intestine, considered by many a "second brain", is reponsible of producing a large amount of neurotransmitters and molecules affecting your mood. Furthermore, the bowel relies on the same systems and connections as the brain does (study)

gut microbiota affects the gut-brain axis

The gut microbiota determines, to some extent, the function of the endothelial cells (study). The connection between the gut microbiota an intestine is clear. Therefore, the gut microbiota is considered part of the gut-brain axis. It improves brain function, and regulates other neuro-endocrine systems such as stress, anxiety, and memory (study)(study)


The gut microbiota refers to the microbial communities inhabiting our digestive tract. Living in a symbiotic relation with humans, the gut microbiota has a big word in our health status.

In this post, we have talked about the role of the gut microbiota in health an disease. Metabolic function, inmunity, cognitive function, and much more upcoming in these years of research!


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  1. Pingback: What are Probiotics - How to Improve your Gut Microbiota - TBS

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