What if the origin of Crohn's disease was in the soil?

What if the origin of Crohn's disease lies in the soil?

January 24, 2025

What if IBD (such as Crohn's disease and ulcerative colitis, see the box below), conditions on the rise that affect 200,000 people in France, were linked to soil pollution? This is the question underlying an original research program called CROPS (CRohn's disease and Pollution of. Soils) currently underway in northern France.

On the program of the first day dedicated to research on IBD and the environment organized in early January 2025 at the General Directorate of Health (Paris) by the patient association afa Crohn RCH France, its first results were presented to the scientific community by its coordinator, Professor Annabelle Deram (University of Lille, civil engineering and geo-environment laboratory, LGCgE).

Crohn's disease: northern France particularly affected

To fully understand this work, it is important to know that in France, the number of new annual cases of Crohn's disease is between 4 and 5 per 100,000 inhabitants.

However, in the north of France, which already has some sad records in terms of public health, we have known for several years that the incidence is higher there (5.7 cases per 100,000 inhabitants). Data from the Epimad register set up at the Lille University Hospital in 1988, a valuable aid which has since enabled researchers and doctors to monitor all patients suffering from IBD in four departments (Nord, Pas-de-Calais, Somme, Seine-Maritime).

But, faced with these conditions whose origin remains unknown and which mainly affect young adults (15% children), recent work by Epimad published in the fall of 2024 in the journal The Lancet showed, in a large-scale study carried out over 30 years, that their incidence continued to increase, particularly in the north of France, especially among children and young adults. For Crohn's disease, the incidence has thus increased from 5.1/105 in 1988-1990 at 7.9/105 in 2015-2017.

In addition, in the four departments covered by Epimad, different geographical areas, local clusters of over and under incidence of IBD, have been identified. It is this territorial heterogeneity that caught the attention of the researchers of the HEROIC consortium, including Professor Deram, an environmentalist far removed from gastroenterology and Crohn's disease, about which she admitted knowing nothing when she began her work.

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“ The soil, we breathe it and we eat it”

Because beyond the influence of air and water on our organisms, perhaps we must also take into account our interactions with the soil. The soil, we breathe it and we eat it”, summarizes the specialist. Three modes of contamination are described: inhalation of dust and gases emitted by the ground, direct skin contact and finally ingestion, either of contaminated food or that, voluntary or involuntary, of particles.

In the end, " It is estimated that an adult ingests an average of 23 mg of soil (the equivalent of about a grain of rice) per day, but it is 100 times more for a child, or 208 mg per day", says Professor Deram.

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Once formed, the project's multidisciplinary team (geologists, chemists, engineers, sociologists, historians, biologists, statisticians, etc.) was able to establish a map of seven different environmental profiles (ranging from the densest urban centers to the least artificialized spaces). Different samples were taken there and now, the aim is to analyze the data to see if links can be established with the clusters of over and under incidence of IBD and the type of environmental profile.

For the moment, the very first results have found an association between clusters of over-incidence of IBD and areas of intensive agriculture (areas of sugar beet and endive cultivation) and historical industrial pollution by metals (arsenic, zinc, copper).But be careful, correlation does not mean causation", warns Professor Deram.

The work must therefore continue with new field campaigns to search for conventional pollutants but also, more originally, for so-called emerging ones (drug residues and endocrine disruptors). Funding must be found, then all that remains is to dig.

What are IBD (inflammatory bowel diseases)?

This term groups together Crohn's disease (CD) and ulcerative colitis (UC), two digestive diseases characterized by inflammation of the wall of a part of the digestive tract, due to a deregulation of the immune system. They mainly affect young adults and develop through inflammatory flare-ups, in a manner that varies greatly from one patient to another, alternating with phases of remission.

In Crohn's disease, inflammation can affect all segments of the digestive tract (from the mouth to the anus), but is most often located in the intestine and frequently affects the terminal ileum, with or without colonic involvement.

In ulcerative colitis, the inflammation always affects the lower part of the rectum and goes up more or less into the colon, but the intestine is never affected.

For more information:

– consult the Inserm file on MICI

– go to the association’s website afa Crohn RCH France

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