The gut microbiota

What it is, what functions it performs, and how we can take care of this important ally of our health.

From here and there on the Web and in magazines we have probably come across this somewhat edgy term. Gut microbiota. I can imagine eyebrows furrowing in puzzlement, eyes scrolling through the first line of the article until halfway through and then listlessly moving on to the next article.

I realize that, microbiota is not an attractive term. It sounds like something boring, distant, that doesn’t affect us-but there is nothing more false. In recent years the gut microbiota has been the focus of much study and research: what has emerged is that if he is healthy then he has beneficial effects on our whole body as well.

In this article, we therefore do justice to the populous community of little creatures living in our digestive tract. We will find out together what it is, what benefits it provides, and how we can take care of our gut microbiota.

The gut microbiota: what is it?

In advertisements we can easily recognize it: it is commonly – and improperly – called bacterial flora!
Here is a simple definition:

The gut microbiota is the set of microorganisms that populate the digestive system, found mainly in the intestines.

Fun fact: We tend to forget, but it is important to remember that there are plenty of “foreign” living things colonizing our bodies! So we are not only talking about the digestive tract but also intimate areas and skin, for example. It is estimated that in a healthy individual the number of cells in the microbiota is almost equal to the number of cells in our body! Not just peanuts, in short.

These microorganisms are our allies: they perform important functions in our bodies, such as protecting us from pathogens and helping regulate our sleep-wake rhythms. What kind of microorganisms populate our intestines? We are talking about more than a trillion bacteria, viruses, fungi and protozoa that communicate with each other continuously and act as one organism. A little creepy said like that, isn’t it? But no fear, we must be grateful to have them with us!

The origin of the microbiota

The moment we are born and the first few years of life are important in laying the foundation for a microbiota that, in the long run, influences overall health and can determine the occurrence of certain types of disease. Natural childbirth is an important occasion: it allows a greater exchange of microorganisms between mother and newborn, with the development of a richer microbiota.

Contact with the mother’s microorganisms also occurs during cesarean delivery, but only with those that inhabit her skin; only natural childbirth allows exchanges with the intestinal and vaginal microbiota. By the same principle,breastfeeding is an important step in the formation of the microbiota.

Not only from mom!

As we will see in the next section, the maternal microbiota is not the only influence on microbiota formation. Contact with environmental microorganisms is also important, and contributes to the development of a good immune system in the newborn. They come from animals, the natural environment, other people or food.

Is the microbiota the same for everyone?

The gut microbiota changes depending onage and several factors such as environment and diet, which, over the course of a day, can transiently change much of its composition. An important characteristic is its resilience, that is, its ability to adapt to changes in environment or diet in order to perform its functions properly.

Everyone’s microbiota is for all intents and purposes “unique” precisely because it depends on many factors. Suffice it to say that not even homozygous twins have the same gut microbiota! The diversity of microorganisms and the quantity of the different species that make up the gut microbiota depend on several factors:

  • the people he comes into contact with
  • the place where he lives
  • his genetic makeup
  • The type of childbirth and breastfeeding she experienced
  • the eating style that follows
  • The lifestyle (sports, smoking, alcohol, drug use…)

What functions does the microbiota perform?

Thehuman being and the microorganisms in his gut have entered into a permanent cohabitation contract. We are in effect symbionts: we are the tenant who works to bring home food, while they do the housework, helping us so much that we are indispensable to our health.

Let us see what the functions of the microbiota are, but without claiming to be complete. If we wanted to go into detail, the functions would be so many that it would be too long. My intent here is to summarize the main roles, which can be divided into three categories:

Metabolic functions

Bacteria are of great help during digestion:

  • help in the final stages of carbohydrate and protein metabolism, converting them into substances useful to the body
  • produce vitamins K and B12
  • synthesize amino acids, the building blocks used to make proteins

Structural functions

Microorganisms in the microbiota help build villi and intestinal wall cells, which are critical for body protection and digestion.

Protective functions

By colonizing the intestinal walls, the microbiota helps us fight pathogens. It also produces substances that can protect us from inflammation and the occurrence of certain types of cancer. The intestinal walls are also lined with a thick layer of mucus, which prevents potentially dangerous bacteria and other foreign matter from entering the bloodstream. Our immune system is then closely linked to the gut microbiota: in fact, 70-80% of our body’s immune cells are found in the gut.

The microbiota then also has effects on different organs distant from the gut because of the substances it produces that, through the bloodstream, reach the different districts of the body. Examples include the liver, cardiovascular system, nervous system, and endocrine system.

I will leave you here with a couple of other functions performed by the microbiota:

  • Certain fatty acids produced by gut bacteria keep the gut healthy by protecting it from inflammation and theonset of cancer.
  • Certain substances produced by the gut microbiota appear to be involved in appetite regulation andweight gain.

Gut microbiota and the brain: what relationship?

It is no coincidence that thegut-or belly-is said to be our second brain, but what is the relationship between microbiota and brain? The gut microbiota is influenced by many factors including diet, exercise and medication intake. In turn, the microbiota produces substances that act on the Central Nervous System. Through the vagus nerve and blood system these substances reach the brain, where they can influencemood and some instinctive behaviors. Several studies note that they can act on fear, stress, and eating behaviors such as anorexia and obesity.

Studies in rodents and humans suggest that changes in the composition of the gut microbiota may influence cognitive function. Administration of probiotics, particularly Bifidobacterium and Lactobacillus, appears to have had promising effects on stress, anxiety, and depression in both animal and human studies. Several studies are currently examining whether the composition of the gut microbiota can help predict an individual’s susceptibility to stress. However, these researches need time to see more clearly.

How to take care of the microbiota?

Let’s cut to the chase: what defines a healthy microbiota? In general, a high diversity of the gut microbiota, that is, the presence of many different microbial strains, is a good indicator of health. Remember, however, that there cannot be an ideal microbiota that is the same for everyone because of individual characteristics, including genetics.

Diseases such as obesity and inflammatory bowel disease, as well as immunological and metabolic diseases, have been associated with states of imbalance in the gut microbiota. While studies are still ongoing to understand how much these conditions may be the cause or the consequence, we can try to take care of the community of microorganisms that inhabit us. How to do it? Here are some general guidelines:

  • Following a diet rich in vegetables and fruits, and generally taking a proper intake of all food groups is definitely the first step
  • Limiting high-fat foods is a good way to prevent inflammatory bowel states, enemies of the microbiota
  • play sports, have an active lifestyle
  • Try to avoid smoking and alcoholic beverages as much as possible
  • use of probiotics and prebiotics can be an ally in this balanced scenario, along with proper use of antibiotics (and then only by prescription)

⦁ Y. Ogawa et al., 2020. ⦁ Gut microbiota depletion by chronic antibiotic treatment alters the sleep/wake architecture and sleep EEG power spectra in mice. Sci Rep 10 (1).
⦁ John F. Cryan et al. 2019 ⦁ The microbiota-Gut-Brain Axism.

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