Scientists find a big cause of irritable bowel syndrome

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In a new study, researchers found the mechanism that explains why some people experience abdominal pain when they eat certain foods.

The finding paves the way for more efficient treatment of irritable bowel syndrome and other food intolerances.

The research was conducted by a team at KU Leuven.

Up to 20% of the world’s population suffers from irritable bowel syndrome (IBS), which causes stomach pain or severe discomfort after eating. This affects their quality of life.

Gluten-free and other diets can provide some relief, but why this works is a mystery, since the patients are not allergic to the foods in question, nor do they have known conditions such as coeliac disease.

In the study, the team found a mechanism that connects certain foods with activation of the cells that release histamine (called mast cells), and subsequent pain and discomfort.

Earlier work showed that blocking histamine, an important component of the immune system, improves the condition of people with IBS.

In a healthy intestine, the immune system does not react to foods, so the first step was to find out what might cause this tolerance to breaking down.

Since people with IBS often report that their symptoms began after a gastrointestinal infection, such as food poisoning, the researchers started with the idea that an infection, while a particular food is present in the gut, might sensitize the immune system to that food.

The researchers were then able to unpick the series of events in the immune response that connected the ingestion of ovalbumin to activation of the mast cells.

They found this immune response only occurred in the part of the intestine infected by the disruptive bacteria. It did not produce more general symptoms of a food allergy.

The team speculates that this points to a spectrum of food-related immune diseases. At one end of the spectrum, the immune response to a food antigen is very local, as in IBS.

At the other end of the spectrum is a food allergy, comprising a generalized condition of severe mast cell activation, with an impact on breathing, blood pressure, and so on.

The researchers then went on to see if people with IBS reacted in the same way.

When food antigens associated with IBS (gluten, wheat, soy and cow milk) were injected into the intestine wall of 12 IBS patients, they produced localized immune reactions similar to that seen in the mice. No reaction was seen in healthy volunteers.

The relatively small number of people involved means this finding needs further confirmation, but it appears significant when considered alongside the earlier clinical trial showing improvement during treatment of IBS patients with antihistaminics.

A larger clinical trial of the antihistamine treatment is currently underway.

The team says mast cells release many more compounds and mediators than just histamine, so if doctors can block the activation of these cells, they will have a much more efficient therapy.

One author of the study is Professor Guy Boeckxstaens, a gastroenterologist at KU Leuven.

The study is published in Nature.

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