Like our gut microbiota, our immune system is established from birth. The delivery method and breastfeeding play an important role in the development of our immunity. The gut microbiota of a baby born by vaginal delivery is more varied than that of one born by caesarean section. This difference explains why two babies of the same weight and size have different levels of immunity. However, this difference gradually disappears, and from the age of 3 onwards, children’s microbiotas are identical, whatever the delivery method.
The immune system protects us against external pathogens. But sometimes it reacts inappropriately.
For example, it can trigger a chronic inflammatory process (when the immune system maintains inflammation although there is no enemy to fight), with numerous consequences for our health. The immune system can also become over-sensitive to certain antigens (foreign substances pinpointed by the body’s defence system, which then produces an antibody to destroy it), triggering an allergic reaction.
The disruption of the immune balance also reduces our tolerance to food, leading to the development of food allergies or intolerances. Some people who always ate fruit without any problem will suddenly develop digestive symptoms (bloating, abdominal pain, etc.). This is explained by an imbalance in the gut microbiota and the resulting breakdown in immune tolerance.
Another example: we know that the symptoms of gluten intolerance (coeliac disease) do not appear in all people with a genetic predisposition; the existence of an associated intestinal dysbiosis is the factor that triggers the onset of the disease.
With the skin, there is a relationship between the skin microbiota and atopic eczema.
The skin microbiota present from birth is a dynamic system that evolves throughout our lives. Adults’ skin microbiota contains various permanent germs and others that are transitory, with wide variations. It is the least stable of all the microbiotas in the human body, and changes under the effect of various factors such as pollution, UV rays from the sun, smoking, stress, antibiotics, household products, etc. All these kinds of external stress create flaws in the skin flora, making it less effective in protecting us. This creates an imbalance (dysbiosis), which plays an important role in the development of diseases like atopic eczema.
When the microbial balance in the skin is disrupted, the bacteria contained in our skin flora become opportunistic pathogens and are perceived by the body as foreign substances (allergens) which lead to the formation of IgE-type antibodies. Chemical mediators (such as histamine) are then released, causing symptoms like redness in the skin.
It is possible to alleviate this disease by balancing the gut and skin microbiotas.
The gut microbiota: the boss in charge of the human body
The gut microbiota is the best-known of all our microbiotas, and the most extensive, containing 39,000 billion microbes divided into 2,500 bacterial species, which fall into two main groups: a “commensal” flora and a pathogenic flora. Every human being has a unique gut microbiota; I call this the microbiotic fingerprint.
The presence of microbes in the intestine has been known for over a century, and it was soon thought that there was a close relationship between the body and the gut microbiota. When this relationship is harmonious, we speak of eubiosis. When the balance is disrupted, we speak of dysbiosis.
Three main factors influence the health of our bacterial flora:
- Exposure to substances that kill the bacterial colonies or disrupt their composition. These include chemical molecules in our environment, certain foods (sugar, ultra-processed foods) and medicines such as antibiotics.
- An insufficient intake of the nutrients that help keep our gut microbiota healthy.
- Stress, which leads to excess production of cortisol (the stress hormone), with harmful effects on the gut microbiota.
How can you tell if you have intestinal dysbiosis?
It is important to understand that there is no single form of intestinal dysbiosis, but an imbalance specific to each pathology. The imbalance of the gut microbiota is not the same in cases of Irritable Bowel Syndrome, obesity or chronic stress, for example. In other words, if you have a chronic or recurring pathology, there is a corresponding intestinal dysbiosis. Work carried out by researchers on humans has revealed a correlation between a characteristic intestinal dysbiosis and a given pathology. In microbiotic medicine, this guides the choice of one or more probiotic strains.
How can we maintain and repair our gut microbiota?
In our gut microbiota, which is an ecosystem in itself, beneficial bacteria live side by side with harmful ones. However, this balance can deteriorate. In this case, we can restore the balance by reseeding our intestinal flora with strains of « good bacteria » called probiotics. But to avoid upsetting the balance, we need to look after our gut microbiota by giving it fibre.
Prebiotics
These are substances, like inulin, which are present in plant fibres and are not digested by our bodies. Prebiotics work by stimulating the activity and growth of certain groups of bacteria, such as bifidobacteria and lactic acid bacteria.
Food probiotics
These are live bacteria or yeasts found in various foods (yoghurt, fermented milk, kefir, fermented vegetables, the rind of certain cheeses, sourdough bread, etc.).
Probiotics in capsules
To treat a pathology, the patient needs to take one or more appropriate strains of probiotics. These strains are available in capsule form, for example Hafnia alvei HA4597 for obesity, or Lactibacillus plantarum 299V for irritable bowel syndrome.
This article is excerpted from one of the files of the PRO BTP Health Observatory: Allergies. You can find other resources related to this study file here.
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