Photo: Mychele Daniau Agence France-Presse
Life on the farm and the contact with the animals offer a real training program for the immune system.
The measures of hygiene and low exposure to bacteria keep germs and infections away, but they would make us also more vulnerable to certain diseases. Have we become too clean ?
“This is not bad to be clean. Hygiene measures have helped increase the life expectancy of 20 to 30 years and infant mortality has declined significantly, ” said Philippe Bégin, allergist at CHU Sainte-Justine and CHUM. Except that at the same time, cases of allergies, asthma and autoimmune diseases have skyrocketed. Can we really establish a link ?
It is by comparing certain regions of the world that the observation is striking. In most western countries, the prevalence of food allergies among preschool children is 10 %. In China and in several asian countries, the rate is maintained under the… 2 %.
Our immune system is a well-oiled machine, but who need learning and to be exposed to some germs to have an appropriate response to the threats. When our environment becomes too sanitized, this exposure declines dramatically.
“We entered in an era where everything must be sterile and antimicrobe. Now, in the grocery store, there are stations of antibacterial soap. One handles the fruit and hand-washing. It reduces our exposure, ” says Emilia Liana Falcone, infectious diseases physician and director of unit of research on the microbiome and the defenses mucosales of the clinical research Institute of Montreal (IRCM).
Have we pushed our immune system to be lazy by exposing it to too few threats ? In fact, it is rather the opposite happened : it became too effective ! In the Face of the organisms, or foods harmless, it deploys now a cargo of soldiers ready for war. “We are seeing more and more auto-immune diseases, where it is downright our body defends itself against itself,” observes Dr. Falcone.
We can also think of the allergies, caused by an inappropriate response of our immune system. “In the case of food allergies, for example, there is a confusion of our defense system in the face of what we should tolerate. The normal response against food, this is obviously to do nothing and let it pass without reacting to it ! “recognizes the allergist Philippe Bégin.
The ” old friends “
This hygiene hypothesis is superimposed over another that may better explain why these diseases are caused by an immune system out of whack explode in industrialized countries : the theory of old friends.
According to Graham Rook, the first researcher to have exposed this theory in 2003, a regular exposure to the organisms without danger early in life could teach our immune system how to react appropriately to real threats to our health. For him, the immune system works like a computer. It is necessary to provide data — here, an exposure to a variety of microbes — for it to learn to identify what it should attack, but also what he must tolerate.
This would explain why children raised on dairy farms are less likely to develop an allergic reaction or asthmatic. Life on the farm and the contact with the animals offer a real training program for the immune system.
Many families would also have a protective effect on children with a maximum exposure to microbes of all kinds. The elders of the family would be more sensitive to infections than the younger. Same thing for children born by caesarean section, which would not have benefited from the exposure to the vaginal flora during birth.
Certainly, the contact with nature has dwindled, we have definitely changed our diet, but it is the misuse of antibiotics which is also shown the finger. “As an infectious diseases physician, the antibiotics are of course my main weapon, but it is necessary to have a judicious use of these drugs. It kills the pathogens but it also kills the bacteria that are beneficial, ” says Dr. Falcone.
Good bacteria sought
In fact, many bacteria inhabit our body and make us valuable services. They constitute what is called the microbiome. We understand its close link with our immune system.
“The microbiome, this is the heart of our immune system, do not hesitate to say Emilia Liana Falcone. There is a constant dialogue between the two and they develop at the same time during our first two years of life. “
Now our colony of good bacteria suffers from a problem of diversity, which would make it less efficient. This would not be a stranger to the rising cases of autoimmune diseases, asthma and allergies.
“When people develop these problems, one often notices a decrease in diversity of the microbiota. If we have a greater variety of bacteria, there is more chance to find good friends, ” says Dr. Falcone.
Why not act on the microbiota by offering just good dating bacterial from childhood ? It is a feasible option in the Dr. Falcone. “Where it has the most impact, it is with the children under two years of age. We try now to determine how we can change from the beginning of their life to support education long-term immune “.