Irritable bowel syndrome (IBS) is an extremely painful condition that affects about 20 percent of the world’s population. But too often, when their doctor can find no allergic responses to any of the foods they’re eating, people who suffer the very real pain and cramping of IBS are told that it’s “all in their head.” If you have IBS, you know that the pain is all too real. Now, researchers have discovered the mechanism that causes IBS, and this is opening the door to more efficient treatment of the condition, as well as ways to treat other food intolerances.
An allergic reaction… sort of
People with IBS often report that their symptoms began after a gastrointestinal infection, such as food poisoning. This fact led scientists at a research university in Belgium to look for the connection between the two… and, they found one. It seems that IBS is a food allergy — sort of. Professor Guy Boeckxstaens is a gastroenterologist and lead author of the study. He and his team started with the idea that an infection that occurs while a particular food is present in the gut might sensitize the immune system to that particular food.
The researchers infected mice with a stomach bug, and at the same time fed them ovalbumin, a protein found in egg white that is commonly used in experiments as a model food antigen (a molecule that causes an immune response). The mice reacted with the release of histamine, as well as digestive intolerance and abdominal pain. Once the infection cleared, the mice were given ovalbumin again, to see if their immune systems had become sensitized to it during their illness. Indeed, they had. Much in the way that we humans often come to form an association between two things that are randomly placed together, the mice continued to release histamines that caused a painful abdominal reaction, even in the absence of infection. Apparently, the digestive systems of the mice were “suggestible.”
And, significantly, this immune response only occurred in the part of the intestine that had been infected by the bacteria. It did not produce more general symptoms of a food allergy. So, a piece of the digestive system had become “allergic” to ovalbumin.
Hope for better IBS treatments
The researchers then went on to see if people with IBS would react in the same way. For a long time, scientists and doctors have wondered why a gluten-free diet, as well as other elimination diets, provides relief to IBS patients when they are not actually allergic to the foods in question and do not have celiac disease, an autoimmune disease caused by a reaction to gluten. When food antigens associated with IBS (gluten, wheat, soy, and cow milk) were injected into the intestine wall of 12 IBS patients, they produced symptoms of IBS: stomach pain, cramping, and diarrhea.
As in the mice, though, these symptoms were limited to the area of the injection and did not affect the rest of the intestine or other organs. Apparently, IBS is a localized food allergy. As a result of these findings, a larger clinical trial of an antihistamine treatment for IBS is currently underway. Dr. Boeckxstaens is hopeful. “ … knowing the mechanism that leads to mast cell activation is crucial, and will lead to novel therapies for these patients. Mast cells release many more compounds and mediators than just histamine, so if you can block the activation of these cells, I believe you will have a much more efficient therapy.”
