Not a week goes by without a scientific article dealing with the microbiota. And we often hear that understanding the microbiota is explaining our illnesses.
But what is exactly the microbiota and how does it influence our condition?
An introduction to our inner forest or what is more commonly called our second brain...
But why is it called "second brain" in the first place?
Because there is a close connection between our brain and our belly:
- a nervous system lining the walls of our intestine (an enteric nervous system made up of neurons) and helping the digestion process. Back into human prehistory and thanks to the invention of fire by Homo erectus, the intestine works less, consumes less energy and allows our brain to use this energy to develop itself
- 95% of the body's serotonin is produced in the belly and then goes up to the hypothalamus, which is involved in the management of our emotions
- it is now possible to make an early diagnosis of neurodegenerative diseases (Parkinson, Alzheimer...) thanks to the analysis of minimally invasive intestinal biopsies.
So we finally understand this second brain, from an evolutionary point of view, should be qualified as the primary or first brain!
But when is the microbiota starting to get organized within our body?
It all starts when our mother gives birth. When we come into the world, through the genital tract, we swallow a number of bacteria that will then become the basis of our intestinal flora or microbiota. A bacterial capital that will accompany us throughout our lives provided that we take the greatest care of it.
For a long time, the belly has remained a black box, with science giving pride to the brain and the rest of our immune system. And it's true that studying the microbiota is not a very satisfying thing to do. The only way to study it is by analyzing the stool. But if you extract the DNA from the bacteria in the stool, you will find that 100,000 billion bacteria live in our intestine. No less than 10x more than in all the cells of our body!
The biggest deforestation of our time
Yet we are not all equal in front of microbiota, and many differences exist between individuals, whether they are healthy or sick. For example, 25% of the population has a depleted microbiota (having lost many microbial populations) and are more susceptible to the development of obesity, Type 2 diabetes, and other autoimmune diseases. This is the case, for example, of babies born by cesarean section who did not have the chance to inoculate their mother's bacteria on the day of delivery.
But the causes of this real deforestation are not only to be found on the side of birth. The analysis of populations living in remote and isolated regions of the modern world, and still having a diet based on hunting and gathering (South America and Africa regions), shows that our modern inner flora is nowadays reduced by 50%!
Researches tend to prove that several factors are involved:
- Low-fiber diet. In only 4 generations, mice feed in the laboratory with such a diet have lost more than 50% of their bacterial diversity.
- A large number of food additives (E433 and E466 emulsifiers widely used in the food industry to mix fats and non-fats components) which are currently being studied in humans
- Heavy use of antibiotics that indiscriminately kill good and bad bacteria. And even a short disturbance of the microbiota has a long-term impact on our metabolism (experiment on mice): increased obesity, allergies, asthma and diabetes.
As a result, we have lost diversity. But have we also lost function?
Unfortunately, we have. The bacteria in our digestive tract, in counterpart for the food we provide them, produce short-chain fatty acids with remarkable anti-inflammatory properties. But not only. Also, by depleting the mouse microbiota with antibiotics, Prof. Zitvogel's team has shown that the response to cancer immunotherapy treatments is much less effective, with the bacteria of the genus Akermansia appearing to be the determining factor.
What solutions are available to us then?
To recover missing gut bacteria, a fecal transplant is a potential solution. This technique has already saved patients infected with Clostridium difficile and proved to be a cure (remission within 24 hours with 94% of patients permanently cured during clinical trials). The US-based company OpenBiome has thus created the largest stool bank in the world for future treatments.
Less invasive (and more delicate :-), new generations of prebiotics are being developed, based on capsules containing stool extracts.
But this is only the beginning of the next great adventure of biotechnology!