by Lisa Keilhofer

The Intelligent Stomach - Our Second Brain.

The stomach - our second brain
The intelligent stomach – our second brain (picture: © wowow –

(Summary of a arte documentary)

In mid-November 2018, the German-French TV channel arte broadcasted a documentary called “The Intelligent Stomach – Our Second Brain”. The title was based on the finding that primal life-forms on our planet did not have a brain, but merely a digestive system guiding them. And only when humans found fire and were able to cook their nutrition, the digestive system was spared so much energy that the brain was able to develop today’s mental capacities. Strictly speaking, our “second brain” is consequently the one in our head. The first brain was our stomach.

To underline this thesis, the documentary backs it up with a series of facts and figures. Our digestive system and the brain of a cat or dog contain approximately the same number of neurones: around 200 million. Also, the structure of neurones in brain and stomach is pretty similar.

The human being as densely populated bacterial habitat.

“Trusting one’s gut”, as the popular saying goes, is not only what we instinctively do, but what is also confirmed by numerics: The human body is home to millions of bacteria. That’s a thousand times the number of stars in our galaxy and one hundred times the number of human cells in our body. Our stomach – or more precisely, our microbiome – is therefore the most densely populated ecosystem on our planet.

Stephen M. Collins, microbiome scientist at McMaster University in Hamilton (Canada) nails it: Humans are above all a vehicle for bacteria. In our body dwell 1-2 kilo of bacteria producing 30% of our calories. Our intake on food is predominantly digested by bacteria. The human uses the energy produced. As a trade-off, the human body offers bacteria home and nourishment. Besides digestion, bacteria help to classify substance as toxic or non-toxic. This makes our gut-microbiome the most important immune system in our body. We live in a symbiosis with bacteria.

How do the bacteria get into our system?

A baby is born sterile. First, the bowel is colonized by bacteria. After that, these decide which further bacteria are admitted to our system or will be defended, until the population consolidates within the first few months of life. This makes every human microbiome individual.

Peril to this complex and precious system are C-sections, replacing breast feeding by formula, excessive hygiene, or the intake of antibiotics by mother or child. What is not explicitly mentioned in the documentary, but commonly known is the fact that “normal microbiomes” are widely challenged by the influence of what we call civilization. The exact reasons are not known today, but it is clear that the microbiome loses its diversity.

Up-to-date science on microbiome

Collins believes that babies might get “vaccinated” directly after birth to receive the best combination of bacteria that is possible. This can be refreshed periodically throughout the life to preserve the microbiome’s great diversity. Today’s research focusses on what that vaccination should ideally contain.

This is the goal of scientists like Dusko Ehrlich at INRA in Jouy-en-Josas (France). His research on deciphering the microbiome found three types of genomes that he calls enterotypes. Interestingly, neither place of residence or birth, nor sex or age seem to be the crucial factor of what enterotype we are. Genes and nutrition, however, count as possible influence. That is the state of the art in science today.

Bacteria against obesity?

Scientists are trying to find out what role the compilation of the microbiome plays for chronical diseases as typ-2-diabetes, cardiovascular diseases, and so on. Read more about the effects of a disturbed microbiome.

Patrice Cani from Université de Louvain (Belgium) made an interesting finding. He examined the intestinal flora of overweight people and found they are lacking the bacterium Akkermansia muciniphila. In a test series, he fed mice with the bacterium and found that the infected individuals showed a lower gain of weight after high-fat diet than the comparison group without the bacterium. The infected mice obviously extracted and saved less energy from the food. The relevant bacterium dwells in the mucus surrounding and protecting our intestinal cells and communicates with these.

This finding calls for attention: Could we simply take A. muciniphila as medicine or dietary supplement? Scientists say, no. 10% of our possibility to digest fat is genetics, 10% regulated by bacteria and the remaining 80% a consequence of what we eat and how much we move.

Is our brain the master of our personality or is it influenced?

But Stephen Collins also draws another interesting conclusion from his tests: He chose two groups of mice, one quiet, one aggressive (so-called Swiss Mice). Then he exchanged the group’s microbiomes. And guess what: Their personalities changed accordingly. The calm mice turned aggressive and vice versa. This proves that our microbiome influences our brain. This finding was received with great attention in science worldwide.

The relevant question, of course, is in how far these results can be transferred to humans. We could cure depressions or aggressions simply by diets or vaccinations. Today’s studies on nutrition supplements like probiotics, however, urge us to act with restraint. The settling of specific bacteria can in no way be vaccinated, but supported in the best case.

At the same time there are studies that are clearly proving that probiotic nutrition can deactivate certain areas of the brain and thus calm negative emotions like stress. Scientists warn to draw conclusions to early, but in any case, it is proven that probiotics have a positive influence on our brain and health.

Do bacteria form a third intelligence in our systems?

Collins summarizes it like this: we are not controlled by bacteria, but they clearly have an influence on what we are and how we behave. According to Collins, besides the brain in our head and the brain in our stomach, we have third form of intelligence in our bodies, the bacteria. This finding leads to a shift of paradigms in science. There is obviously no clear border between the self and the outside, but a complex system of reality, consisting of not-yet explored networks of thousands of genes, millions of neurones, and hundreds of millions of bacteria. The complexity is – yet – beyond our means of understanding.

Lisa Keilhofer
Lisa Keilhofer

Lisa Keilhofer studied at the University of Regensburg. She works in internationalization and as a freelance editor.

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