Benefits of Gut Bacteria and Their Surprising Role in Human Health

Heather Campbell
 min read

The benefits of gut bacteria are numerous, and we’re just beginning to understand more about it.

Benefits of Gut Bacteria and Their Surprising Role in Human HealthDid you know that bacteria are not just harmful microbes? Indeed, those in our digestive tract, forming part of our intestinal microbiota, are vital to our health.

As a whole, gut bacteria are essential to the immune system and understanding how they work could also offer new avenues for treatment. Microorganisms that make up the intestinal microbiota provide immune, digestive, neurological, and metabolic functions and are wonderfully unique to each individual.

Let’s discover together the benefits of these intestinal bacteria.

Benefits of gut bacteria: Introduction

The intestinal flora or bacterial flora that we often hear about is better known as “microbiota” and corresponds to the crucial bacterial population that our body shelters, mainly the one found in the digestive tract.

According to some estimates, there are between 15 and 100 bacteria per cell, which proves that we have a lot of bacteria in our bodies, but what are these bacteria used for?

Are they really good for our bodies? What are the benefits of gut bacteria? Read on for more.

Understanding the role of the intestinal microbiota

A microbiota is defined as the set of microorganisms (bacteria, viruses, parasites, and non-pathogenic fungi) that live in a specific environment.

In our body, there are different microbiota: in the skin, mouth, vagina, lungs, etc.

The intestinal microbiota is the most “populated” of them, as it harbors approximately 1000 microorganisms and is mainly located in the small intestine and the colon.

It is distributed between the digestive tract cavity and the protective biofilm formed by the intestinal mucus that covers its inner wall.

The stomach’s acidity is not favorable to the presence of most microorganisms and that’s why our stomach has a hundred million times fewer bacteria than the colon.

For over a century,  humans have known about microorganisms in the intestine, and studies have assumed a symbiosis between our body and this flora.

Unfortunately, the technical means available to study the details of this interaction were limited. For example, only a minority of bacterial species of the gut microbiota can be easily cultured in vitro.

Developing high-throughput sequencing of genetic material gave new life to this research.

Although still imperfect to thoroughly analyze such a large number of genomes, this approach allows for obtaining a good deal of information on the global composition of a microbiota and is often combined with lipidomic and metabolomic analyses to identify the substances produced by this ecosystem.

Thus, researchers can describe in more detail the nature of host-microbiota interactions: those of the microorganisms between themselves and their impact on the organism’s functioning.

As a result, the benefits of gut bacteria is becoming increasingly well known and it is known to play a role in digestive, metabolic, immune, and neurological functions.

Moreover, dysbiosis, a qualitative and/or functional alteration of the intestinal microbiota, is a good way to explain certain diseases, including those underpinned by autoimmune or inflammatory mechanisms.

The viruses that infect bacteria (called “phages”) are also very numerous in our microbiota. Indeed, they can modify the bacterial populations, their genetic heritage, and the latter’s expression.

To each his own microbiota

The characterization of all the microbial genomes found in the intestine by high-throughput sequencing has made it possible to identify many different species, most of which correspond to bacteria.

The intestinal microbiota is unique in quality and quantity and specific to each individual.

Of the 150 species of bacteria that make up the average healthy individual’s microbiota, only half are commonly found from one individual to another.

However, there is a common base of about 20 species present in all human beings, in charge of the essential functions of the microbiota.

A unique ecosystem created from birth

The development of a child’s good health would directly depend on the microbiota. Indeed, it is thought that the mother’s microbiota plays a determining role in fetal development.

A person’s microbiota is gradually built up from birth: first in contact with vaginal and fecal flora after a vaginal delivery or in contact with environmental microorganisms in the case of a c-section.

Bacterial colonization occurs gradually and in a specific order:

  • First of all, the first intestinal bacteria need oxygen to multiply.
  • Then, by consuming the oxygen present in the intestine, they favor the implantation of bacteria which increase only in the absence of oxygen.

During the first years of life, the composition of the intestinal microbiota will evolve in quantity and quality under the influence of several factors:

  • Food diversification
  • Genetics
  • The level of hygiene
  • Medical treatments received
  • And the environment.

Secondly, this composition remains pretty stable, although this stability varies from one person to another.

Fluctuating sex hormones (testosterones and estrogens) can have an impact on the composition of the gut microbiota, as can:

  • Diseases
  • Medical treatments
  • Changes in lifestyle or diet

All this can indeed modify the microbiota in a more or less lasting way.

Let’s take the example of an antibiotic treatment: it will reduce the quality and quantity of the microbiota over several days to several weeks. Species present before treatment can recover largely, but differences may persist.

When the microbiota does the body a favor

The intestinal microbiota ensures its own metabolism by drawing on our food (including dietary fiber). Moreover, the microorganisms that compose it play a direct role in digestion:

  • They help assimilate nutrients thanks to a set of enzymes that human cells do not have.
  • They ensure the fermentation of substrates and non-digestible food residues.
  • They participate in synthesizing specific vitamins (vitamin K and B vitamins) and three essential amino acids: valine, leucine, and isoleucine.
  • They ensure the hydrolysis of starch, polysaccharides, and cellulose.
  • They regulate several metabolic pathways: the absorption of fatty acids, calcium, magnesium, etc.

Studies have been conducted on animals raised without microbiota (so-called axenic or germ-free animals). The results show that these animals have energy requirements 30% higher than those of a normal animal.

The microbiota acts on the global functioning of the digestive tract: axenic animals have a slowed down digestive tract transit.

Indeed, the differentiation of their intestinal wall cells is incomplete, while the blood network that irrigates it and the local network of immune cells are less dense than in animals with a gut microbiota.

This vascular system has a vital role in nutritional and hormonal metabolism and the docking of immune cells within the intestinal wall.

The intestinal microbiota is also fully involved in the functioning of the intestinal immune system, which is essential for the barrier role of the intestinal wall.

From the first years of life, the microbiota is necessary for the intestinal immunity to learn to distinguish friendly species (commensal) from pathogens.

Studies have shown that the immune system of axenic mice is abnormal. Indeed, their Peyer’s patches, which induce immunity at the intestinal level, are immature and their lymphocytes, which are effectors of immune reactions, are in reduced number.

Their spleen and lymph nodes, major organs for the body’s overall immunity, also have structural and functional abnormalities.

Moreover, it seems that bacteria such as Escherichia coli fight directly against the colonization of the digestive tract by pathogenic species, competition, and production of bactericidal substances.

Microbiota and inflammation

Inflammation is an essential biological process that is closely related to immunity, namely:

  • A physiological level of inflammation is vital for immune activation and control of the microbiota.
  • And important inflammatory reactions are triggered in the presence of pathogenic species.

The latter mechanism relies on the presence of inflammatory bacterial components, such as lipopolysaccharides (LPS), present on the surface of certain bacteria.

These antigens provoke an immune response that leads to the production of pro-inflammatory mediators (cytokines) by macrophages in the intestine.

Local inflammation is triggered, and the permeability of the intestinal wall increases. As a result, LPS can then pass through the latter, enter the bloodstream, and cause an inflammatory phenomenon in other target tissues.

The intestinal microbiota in figures

Generally, most of the bacteria in our digestive system are found in the colon.

In total, we have 70 oz of bacteria in our digestive tract, and the colon has the most bacteria, with 100 billion bacteria in 0.03 oz of stool!

The microbiota is not innate, i.e., we are not born with it. During the first years of life, a child will build up its bacterial population from the bacteria in its environment (through contact with the microbiota of the skin of adults, through food, etc.).

By the age of two, each of us has an “adult” microbiota. Then, the microbiota changes throughout our lives, renewing itself and becoming more fragile as we age.

Consequently, each person has their own microbiota, their own bacterial signature, resulting from their personal history, depending on their diet, age, sex, body type, lifestyle, etc.

Two-thirds of the intestinal bacteria are specific to each person, and the last third is common.

What is the purpose of our intestinal flora?

One might ask, what is the purpose of the billions of bacteria that inhabit our bodies? It is essential to know that they have four main functions:

  • Degradation of food compounds (such as fiber)
  • The development of the digestive tract
  • The production of vitamins (K, B12, B8…)
  • And especially the immune defense.

The microbiota acts as an antimicrobial barrier that prevents the implantation of harmful bacteria. Therefore, our bacteria interact with immune system cells for an efficient response.

Without microbiota, the immune system is atrophied. In fact, this interaction is significant in stimulating the immune system.

During our childhood, contact with microorganisms different from the microbiota can positively influence the maturation of the immune system.

This aligns with the hygienic theory developed around 1980 that strict hygienic conditions in childhood would lead to diseases in adulthood. For example, one could say that a bit of dirt can’t hurt your child.

Sensitive to our personal history, our microbiota evolves continuously and can also become fragile.

Although its functioning remains partly mysterious, studies suspect that an imbalance of this microbiota could be at the origin of various pathologies such as:

  • Inflammatory diseases (including Crohn’s disease)
  • Irritable bowel syndrome
  • Functional intestinal disorders
  • Obesity.

Related postGut Microbiome and Obesity, Gut Dysbiosis and Metabolic Syndrome: Are They Linked?

Antibiotics unbalance our intestinal microbiota

According to some research, it has been shown that the microbiota can promote fat storage.

Therefore, obese people would have a higher ratio of Firmicutes to Bacteroidetes (i.e., a lower proportion of Bacteroidetes) than slim people.

It is thought that during evolution, the human microbiota can extract as much energy as possible from food. At the time, this property allowed to optimize the little food available. However, at present, it would play against us and would be one of the factors of the high prevalence of obesity.

Several factors can contribute to these imbalances, including taking antibiotics (which kill bacteria), eating a high-fiber diet, and having a colonoscopy.

Tip: Check our other article to learn all about How to Maintain a Healthy Gut Microbiome with Antibiotics, Probiotics, Prebiotics, Symbiotics and Others

Bacterial groups in the microbiota

The study of this microbiota is recent, and the bacteria that compose it are far from having revealed all their secrets.

Researchers are far from having identified all the species present and do not know much about their mode of operation.

The main difficulty in studying them concerns access to these intestinal bacteria. Indeed, 85% of the microbiota is not cultivable in vitro (most of them die very quickly in the presence of oxygen).

At the beginning of the century, alternatives were put in place to accurately determine the gut microbiota: determination of the species present, quantity, etc.

Then, oxygen-free (anaerobic) culture systems were created but could not identify all bacteria.

Sequencing of their genome seems useful in characterizing them. Metagenomics is the sequencing of all the bacterial genomes of a microbiota. It is mainly thanks to this new approach that scientists will be able to learn more.

The bacterial signature of our intestines

Researchers have recently discovered the existence of three bacterial groups or enterotypes that characterize each individual which help us understand the benefits of gut bacteria.

Indeed, the human population can be divided into three distinct bacterial groups, independent of the place of residence, sex, health status, or the age of the individuals.

To reach this conclusion, the researchers studied the intestinal bacteria of more than 40 people of European, American, and Japanese origin.

As a result, they were able to determine the existence of:

  • Enterotype 1, where Bacteroides bacteria are the most numerous.
  • Enterotype 2, where Prevotella are found.
  • Enterotype 3, with Ruminococcus.

These results would lead to a classification while opening the door to new diagnostic tools and even treatments for pathologies related to the microbiota, such as obesity or Crohn’s disease.

Intestinal bacterial flora and probiotics

It seems that food is the first ally of our microbiota. Indeed, the bacteria naturally present in yogurts and other fermented milks positively affect our bodies.

In particular, bifides are present in fermented milks and seem to affect the speed of transit of food, bloating in adults, and infantile diarrhea.

These living bacteria correspond to the official definition of probiotics of the World Health Organization (WHO), namely that they are “living microorganisms which, when administered in adequate quantities, produce a health benefit for the host.”

But beware: probiotics cannot restore the intestinal flora, as the promotion of certain foods may suggest.

Most probiotic strains are lactobacilli and bifidobacteria. They could help us fight certain digestive disorders and strengthen the interaction of the microbiota with the immune system.

Benefits of gut bacteria: Conclusion

It is essential to have a balanced microbiota if you want a healthy body.

Indeed, knowing more about our microbiota can help increase our knowledge about the mechanisms at work in many pathologies such as obesity, chronic inflammatory diseases, etc.

We can find good bacteria in our food and thus promote a healthy microbiota and enjoy the benefits of gut bacteria.

These microorganisms that make up the intestinal microbiota provide immune, digestive, neurological, and metabolic functions.

And finally, let’s also stress that the microbiota of each individual is absolutely unique.

About Heather Campbell

As a nutritionist, my field of specialization is science-based nutritional advice but more importantly, it is my goal to share capturing and inspiring stories, examples and solutions which can help plus-size individuals overcome their specific difficulties. Read More