Millions of people suffer from irritable bowel syndrome (IBS), a condition characterized by bloating, diarrhea, and abdominal pain after eating certain foods. A recent study published in Nature sheds light on one of the mechanisms that lead to this condition.
Have you ever had abdominal pain after eating a type of food, even though you are not allergic to it or do not have celiac disease? It may be irritable bowel syndrome (IBS), a disease that is not severe but disabling when it becomes chronic. It is estimated that IBS affects up to 15% of the US population. Although not a new condition its causes are still poorly understood and are likely multifactorial. A gastroenterologist from the University of Leuven, Belgium, has identified one of the mechanisms underlying the occurrence of this diet-related digestif system condition.
A disease that occurs after an infection
In a healthy gut, immune cells are not stimulated by the presence of food. In an IBS-affected gut, certain foods stimulate mast cells, cells of innate immunity that secrete histamine, the molecule responsible for abdominal pain.
To determine the origin of this disorder, doctors assumed that many people suffer from IBS as a result of an intestinal infection. Therefore, they proposed that the immune system became sensitive to food in the gut at the same time as the infection.
To test their hypothesis, they simulated an intestinal infection in mice. The mice were infected with a bacterium and simultaneously fed ovalbumin, an egg protein commonly used as a food antigen. After the infection was thwarted by the immune system, the doctors fed the animals the egg protein ovalbumin again.
They then observed in previously infected mice mast cell activation, histamine release, and abdominal pain, while the mice that were not infected with the bacteria remained pain-free.
In irritable bowel syndrome, the abnormal immune response is local and not systemic, as in a classic food allergy; histamine is released only in the area destabilized by the bacterial infection. Medical researchers have observed the same phenomenon in humans.
“At one end of the spectrum, the immune response to a food antigen is very local, as in irritable bowel syndrome. At the other end of the spectrum is food allergy, which involves a generalized state of severe mast cell activation with effects on respiration, blood pressure, etc.,” says Professor Guy Boeckxstaens, the author of this paper.