2024-01-15 16:43:11
If France is one of the main players in agriculture in Europehowever, it faces growing challenges in food production and of crop protection once morest pests and “weeds”.
In this quest to meet the needs of a growing world population, the use of phytosanitary products has long been considered the saving solution. However, the environmental impact of these chemical compounds (which are part of pesticides) is revealed public health concernwhich gives rise to a lively debate on their use, as evidenced by the recent excitement around the question of renewal of glyphosate.
But this molecule is not the only one to pose a problem. Another emblematic case is that of chlorpyrifos. Banned in France since 2020, we still find a certain quantity in the soil of our country. What do we know regarding its effects on health, and in particular on our intestinal microbiota?
Omnipresence of pesticides and health
Despite the regulations put in place to limit their use, the exposure of the French population to pesticides remains significant, particularly in the Hauts de France region. These products are in fact found in the air we breathe, in the water we drink and in our diet more generally.
This omnipresence represents a risk for humans, because the toxicity of these substances does not stop at targeted organisms. For several years, a question has been asked with increasing insistence: might it be that certain harmful effects observed in humans, or even the occurrence of certain diseases, are linked to a exposure to pesticides ?
Some studies indeed seem to have found evidence of the possible role of exposure to pesticides in the occurrence of human diseases such as cancers, Alzheimer’s disease, Parkinson’s disease, attention deficit hyperactivity disorder, autism, birth defects and infertility.
In such a context, the question of chronic exposure to a mixture of pesticide residues becomes a major health issue. This is all the more important when this exposure takes place during the perinatal period because pregnancy is a particular period of life, marked by a certain vulnerability of the mother but also of the unborn child.
However, in 2021, the expertise of the National Institute of Medical Research (Inserm) “Pesticides and effects on health”, indicated that analyzes carried out on meconium samples (the first stools of the newborn) collected from ‘around fifty healthy newborns revealed “the presence of chlorpyrifos, diazinon, propoxur and isoproturon in the majority of samples. »
What is chlorpyrifos?
The chlorpyrifos is an insecticide that has been largely used in agriculture for several decades.
This insecticide is part of the organophosphate family, molecules that target the nervous system of insects. Due to its neurotoxicity and harmful effects on the environment and health, restrictions have been placed on its use. Works evaluating environmental risk factors for neurodegenerative diseases have indeed revealed that exposure to chlorpyrifos is associated with cognitive impairment, oxidative stress and neuronal damage.
In 2020, a ban on the use of this pesticide was announced, with a deadline set in 2022, in favor of the transition towards more sustainable and environmentally friendly agriculture. However, in 2023, a certain quantity of chlorpyrifos residues will still be found in French soils.
Chlopyrifos molecule.
NEUROtiker/Wikimedia
This varies depending on several factors, such as environmental conditions, previous agricultural practices, and natural decomposition processes. Indeed, chlorpyrifos, applied for several decades and in large quantities, binds to plants, soil particles or sediments. After a certain time, its main fraction is either volatilized, hydrolyzed, or biodegraded depending on the physicochemical properties of the pesticide. Volatilization depends on concentration, temperature and soil properties. As for its biodegradation, it depends on the type and mixture of microorganisms inhabiting the soil.
All these factors mean that the half-life of this pesticide (the time taken for a substance to lose half of its activity) is not constant: it can be of a hundred days like persisting up to 17 years.
The ban on chlorpyrifos did not, moreover, include all organophosphate pesticides. A range of other molecules, which we do not talk regarding, belonging to this same family, are used such as diazinon, malathion and parathion. If the main effect of these molecules is neurotoxicof the recent studies demonstrate that these molecules also act on the stress response provided by the intestinal microbiota, and on its involvement in carbohydrate metabolism.
This is why research into the health effects of organophosphate pesticides, and chlorpyrifos in particular, continues. Work has revealed worrying results regarding its impact on the intestinal microbiota.
The intestinal microbiota, a “symbiotic organ”
The intestinal microbiota is not a simple community of microorganisms colonizing our digestive tract. Nowadays, it is rather seen as playing the role of an organ essential to various functions of our body. Notably, this is our body’s first physical barrier to contact with food contaminants such as chlorpyrifos.
However, it is not an organ like any other, but rather a “symbiotic organ”: the micro-organisms which compose it (mainly bacteria), establish a symbiosis with our body, in other words an intimate association , sustainable, and in this case, mutually beneficial.
Indeed, the intestinal microbiota is not isolated from the rest of our body. The microorganisms that compose it participate in the digestion of food, play a role in the synthesis of certain vitamins, intervene in immune defenses, and, via the molecules that they produce while doing all this, regulate certain metabolic pathways (absorption fatty acids, calcium and magnesium in particular).
A few figures allow us to understand the importance of this association: our intestinal microbiota is composed of approximately 1014 microorganisms, or 100,000 billion cells, in other words a number that exceeds that of the cells in our own body. It is estimated that the microbiota contains 3 million genes, while our own genome only contains approximately 23,000. One wonders if we are not more “bacterial” than human…
The Escherichia coli bacteria is present within the intestinal flora (scanning electron micrograph, in false colors). National Institute of Allergy and Infectious Diseases/National Institutes of Health
This intestinal microbial ecosystem has become an important subject of research due to its involvement in numerous pathologies, such as obesity, type 2 diabetes and colon cancer. We know that it differs in pregnant women.
Indeed, hormonal variations (estrogen and progesterone) and alterations in the immune system that occur during pregnancy influence the bacterial composition as well as the functions of the intestinal microbiota. This leads to metabolic disturbances which can lead to obesity or so-called “gestational” diabetes.
In such a context, the question of a possible increased sensitivity of pregnant women to food contaminants therefore arises acutely.
Chlorpyrifos and disruption of the intestinal microbiota
Recent studies showed that the ingestion, by pregnant rats, of foods containing pesticides, and in particular chlorpyrifos, was associated with alterations in the composition of the intestinal microbiota.
A decrease in populations of certain beneficial bacteria and an increase in potentially pathogenic species in mothers and offspring were observed. Alongside these microbiological consequences, the results showed a disruption of the lipid and glycemic profile by chlorpyrifos, hence its link with the occurrence of obesity and type 2 diabetes.
Chlorpyrifos spread on crops can end up in our body. Maria Abou Diwan, Provided by the author
As we have seen, our intestinal microbiota is in constant dialogue with our body. And in particular with two very important functional barriers to protect us from invaders: the intestinal barrier and the blood-brain barrier, which protects the brain. This connection is defined as the microbiota-gut-brain axis.
However, it has been demonstrated that chlorpyrifos not only acts directly on the nervous system, but that it also disrupts the microbial environment of the intestine. Which has consequences that go beyond our digestive tract alone.
Disturbances of the intestinal microbiota which can have remote repercussions
Deregulation of the microbiota is grouped under the term “intestinal dysbiosis”. The consequences of such disturbances include modifications in the composition of the cocktail of molecules produced during the functioning of the intestinal microbiota, which can have an impact on other organs.
We know, for example, that changes in the production of short-chain fatty acids, produced by “beneficial” bacteria in the microbiota, impact the permeability of the intestinal barrier and induce inflammation of the intestine.
This will also allow the passage of microorganisms and potentially harmful substances into the bloodstream and, ultimately, to the brain across the blood-brain barrier, whose waterproofing is impacted by chlorpyrifos.
This phenomenon, which we call “bacterial translocation”might contribute to the development of maladies chronic inflammatory bowel disease (IBD), metabolic diseases and neurological problems, such as anxiety or depression.
These results indicate that this insecticide might thus completely disrupt communication within the microbiota-intestine-brain axis, and therefore have effects on several organs of the body.
With this in mind, it seems necessary to continue studies on this molecule and pesticide residues in general in order to better understand their involvement in long-term diseases and propose effective nutritional preventive strategies.
How can we prevent these effects and protect our intestinal microbiota?
These pathological phenomena, although alarming, seem to be able to be countered. Recent studies, including those from our laboratory, PeriToxshowed that some prebiotics might be beneficial in the treatment of intestinal dysfunction, reducing the risk of inflammatory diseases and colorectal cancer.
THE prebiotics are nutrients that have the capacity to promote the growth of “good bacteria” present within the intestinal microbiota (referred to by the generic term “probiotics”). Concretely, these are elements on which these beneficial bacteria will be able to feed.
Prebiotics can be provided through food. Examples include dietary fibers such as fructo-oligosaccharides (FOS) (like inulin), galacto-oligosaccharides (GOS), trans-galacto-oligosaccharides (TOS) and resistant starch found in many fruits, vegetables (such as chicory and endives), cereals and milk. They can also be taken as a supplement.
Furthermore, diet can also provide probioticslike the bacteria found in yogurt (Lactobacilli).
Supplementation with probiotics and prebiotics is now considered a promising approach to mitigate the negative effects of food contaminants. Studies carried out at the PériTox laboratory have, for example, shown that inulin supplementation (a dietary fiber with a prebiotic effect) hinders the effects of chlorpyrifosby restoring the balance within the intestinal flora.
Promoting a diet low in pesticide residues, called “organic”, might also reduce our exposure. Indeed, according to the latest report from the European Food Safety Authority (EFSA), foods of plant origin from organic farming have lower levels of pesticide residues.
Thinking carefully regarding our diet, especially during pregnancy, is therefore the key to protecting the health of our intestinal microbiota and that of our unborn child from food contaminants. While waiting for alternative strategies to the use of pesticides in agriculture which are beginning to emerge, to gain momentum…
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