Bacteria, however, make up 98% of the microbiota population, and each type has its own role. For example, there is a type of bacteria that produces short-chain fatty acids, SCFAs, which nourish the cells of the colon and have an anti-inflammatory function, or bacteria that regulate the absorption of various nutrients, and so on.
In short, the bacterial population of our microbiota has a function that is proving ever more central in our body. According to various studies carried out on mice, the microbiota may even influence our behaviour. Mice deprived of a microbiota, known as germ-free, which were kept in sterile environments from birth, were seen to behave more impulsively than mice with a microbiota.
Moreover, it seems that our bacterial friends may also play a role in our choice of foods: since different bacterial populations exist, it is theorised that some of them, by feeding on certain foods more than others, “request” that food, sending signals that push us to eat it.
Still on the gut–brain axis, it has been observed that when the microbiota of people suffering from depression was transplanted into mice, the latter displayed behaviour typical of the symptoms of depression. So we are increasingly seeing how our mind is influenced by our gut and vice versa.
The potential consequences for obesity are also hugely important. Germ-free mice were seen to remain lean despite high-calorie diets. The microbiota of a lean mouse was then introduced into some of these mice, and that of a heavier mouse into another germ-free mouse, and it was seen that, on the same diet, the lean mouse stayed lean while the heavier one tended to put on weight. The explanation is that the microbiota is fundamental in how nutrients are assimilated. This could be a new frontier in the treatment of obesity.
But how does the microbiota form? It begins at birth, with passage through the birth canal, then with breastfeeding, and then with everything the baby comes into contact with. Then, of course, diet is extremely important. This is why each of us has a microbiota that is, in some respects, different.
The microbiota is also fundamental in modulating the immune system and in immunity in general. So much so that researchers are studying the correlations between autoimmune diseases and various allergies and differences in exposure to the various bacteria that go on to make up the microbiota, such as caesarean or natural birth.
The microbiota is influenced by many factors: first of all diet and lifestyle habits, then infections, medicines, hormonal changes, the immune system, intestinal permeability and the enteric nervous system. With diet, we must always bear in mind that we are feeding certain bacterial species more than others, which is why we should try to prefer a diet made up as far as possible of unprocessed foods, fruit, vegetables, little sugar and so on, because these substances will have different effects on our microbiota.
In predisposed people, alterations of the microbiota can lead to irritable bowel syndrome, ulcerative colitis, Crohn’s disease and so on, so be careful what you eat. There are foods that are known to be pro-inflammatory, such as sugars, and anti-inflammatory foods, such as vegetables.
To look after our microbiota there are probiotics and prebiotics, which can be used when there are alterations, such as when taking an antibiotic and there is a risk of intestinal dysbiosis. Probiotics are the bacterial strains themselves, while prebiotics are the nourishment given to certain bacteria. There are also postbiotics, which are the substances produced by the bacteria themselves, and synbiotics, which are formulations of prebiotics and probiotics together. Naturally, supplementation should be considered on the advice of a professional.
In short, taking care of our diet and our lifestyle means taking care of our microbiota, which is like a conductor of the orchestra of our overall health.
