Updated: Mar 15, 2022
Our immune system is our first line of defence when we are exposed to a virus, like Covid-19. A healthy immune system depends on many factors, like nutrients and vitamins and our general health. A healthy intestinal flora is essential to our immune system, and the interaction between the two often defines the body's responses to infection.
What is the immune system?
The immune system includes cells, molecules, antibodies, and physical barriers, such as skin and intestinal mucosa. Its primary role is to define what belongs to us and what does not belong to us. It serves as our body's central communication system with the environment.
When a pathogen enters our body, the immune system detects it, recognizes it, and starts chain reactions to fight it. In the case of a viral infection, the immune system's appropriate answer aims to stop virus duplication and decrease the viral load.
When our immune system is healthy and works well, these reactions create a natural and adapted inflammation producing mild symptoms, and leading to a full recovery. When it is insufficient, the virus duplicates more and more in different cells, creating massive tissues damages injuring our body in different ways. Finally, when our immune system is impaired and overreacting, the cytokines production and inflammation get out of hand, creating severe symptoms.
More than 70% of immune cells are found in the gut. Historically, food contained many pathogens, and the intestinal mucosa is an important centre for our protection against the environment. The gut is then the front line of defence for our body.
What is the intestinal flora?
The intestinal microbiota is a vast and diverse population of more than 10,000 billion microorganisms. It is mainly composed of 800 to 1000 different species of bacteria and a small number of yeast, virus and parasites, all living in harmony in our intestines.
There are no bacteria in the mother's womb, so the baby's first contact with microorganisms happens at birth. From this first contact, bacteria colonize the intestines, the skin and other mucous membranes to create different microbiomes. The gut microbiome fully develops during the first three years of life, influenced by diet, environment and drug treatments. At three years old, our intestinal flora is fully defined. There is great diversity in the flora composition between individuals. Our gut microbiome's profile is specific to each of us, like a fingerprint.
The first role of the microbiota is to help digestion. Scientists thought it was its only role in our body for a long time. A few decades ago, they discovered that bacteria produce molecules that act as messengers for our various organs while digesting foods. These molecules, called postbiotics, have been intensely studied since then, showing the complexity and the essential role of the intestinal flora in our body. These discoveries have led us to call our gut "the second brain", emphasizing its critical role in our health.
Why does a strong immune system need a healthy gut?
The relationship between the immune system and the intestinal flora is complex and essential. The healthy bacteria don't belong to us. We need our immune system to recognize them, tolerate them as if they were part of our body, and differentiate them from other pathogens we are exposed to.
The development of the immune system occurs in the first years of life, at the same time as the intestinal microbiota is growing, allowing them both to develop in symbiosis during early childhood. While the immune system accepts the bacteria colonization in our gut, the bacteria, in return, develop capacities to calibrate and support the immune system.
The intestinal flora protects us in two ways. First, bacteria colonize and occupy the space on the intestinal mucosa surface, preventing other organisms from growing, and invading us through the guts. They also secrete molecules and messengers to support and stimulate the immune system. In the early stages of an infection, the cooperation between the gut and the immune system partly defines the appropriate response.
As most of the immune cells are present in the gut, what is happening there influences our immune system's overall response. When the intestinal flora is unbalanced, what we call a dysbiosis, the messages sent from the bacteria to the general immune system get through badly. The immune response can be affected and inadequate. When inflammation occurs in our gut, the local immune system reacts to it. While it is busy fighting there, it is distracted and has fewer resources to protect our body from pathogens. It explains why people suffering from gut inflammation and dysbiosis can be more susceptible to infections.
How do you know your intestinal flora is out of balance?
Many factors influence gut health. An unbalanced diet, lack of exercise, stress, or hormonal changes can be the starting point of a gut imbalance. A dysbiosis leads to various symptoms, from bloating, digestive disorders, or food intolerances to skin problems or even anxiety and mood disorders.
Researchers have recently found that some species are essential to support the immune response. Several studies have shown a real correlation between the deficit of certain species (Bifidobacterium bifidum, Bifidobacterium longum, lactobacillus adolescentis, Faecaibacterium prausnitzii) and the severity of symptoms among patients infected by the virus Covid-19. It is now possible to perform a simple qPCR test of the microbiome to analyze and highlight a dysbiosis.
Restoring the intestinal flora is often a long process and requires a holistic approach. It combines a balanced diet rich in fibres with probiotics and prebiotics. Practising regular exercise stress and anxiety management directly improve the intestinal flora. Complementary medicine such as lymphatic drainage, reiki, acupuncture, osteopathy, or even hypnotherapy, can all be a real help in restoring our microbiota and thus strengthening our overall health.