Celiac disease is the other end of the food allergy and intolerance spectrum. Celiac disease does not involve IgE, it involves IgG and IgA. These immunoglobulins don’t cause itching, they are the immunoglobulins that your body uses to attack bacteria, viruses, and sometimes microbes. They don’t trigger histamine release, which means they don’t cause itching. But they do trigger inflammation.
IgA and IgG are part of a larger immune response that you know all too well. When you have a cold, the flu, or a bad case of food poisoning, part of your symptoms are really due to the immune system and how it’s attacking the virus or bacteria that is attacking you. IgA and IgG are the bulk of your immunoglobulin response to these infections.
IgA is present mostly in the gut while IgG is present in the gut, breastmilk, and your blood. Foods, from the moment they touch your lips, are having their proteins digested and assimilated by your body as nutrients. These proteins do cross the gut lining, whether in the mouth or the small intestine, and can provoke an immune response, and therefore inflammation, anywhere along the gut, from entrance to exit. These immune responses, however, may not be noticeable. They may start moments or hours after eating. They may include responses anywhere along the length of the gut, whether it’s a headache triggered as soon as you eat the food or one that comes on hours after you’ve eaten it. Maybe it isn’t a headache, but abdominal pain. Maybe it isn’t pain at all, but diarrhea, gas, or constipation. It may also be that these symptoms are due to interactions between the food and the microbiome, rather than your immune system and the food itself (more on that in the next section).
IgA and IgG are powerful stimulators of the immune response. When they are being triggered, they’re also simultaneously triggering the body’s stress responses. This can lead to a vicious cycle in which the food, which you keep eating, constantly stresses your system, robbing your immune system of its power to fight the real threats to your health, and even leading to confusion in the immune system that causes it to destroy your own tissues.
I explain how things go wrong in, “How does your immune system work, and how do things go wrong?”
If IgA and IgG target foods that you keep eating, you essentially turn your gut into an area that your immune system thinks is an infection. If you think that sounds like a problem, you’re right. What happens next is all too predictable — your body stops trying to digest your food and starts trying to kill it.
That means producing lots of immunoglobulins to the gut, where they turn acute inflammation into chronic inflammation.
Not only do IgA and IgG mediated responses cause inflammation in the gut, they can cause inflammation elsewhere, which means symptoms far away from the gut.
So many of our food intolerances, whether the symptoms are abdominal pain, headaches, diarrhea, constipation — the list goes on — are due to these IgA and IgG-mediated responses.