Advertisements have been popping up all over the internet for EverlyWell Food Sensitivity Test. (And they were on Shark Tank). The company claims, “This at-home test measures your body’s IgG response to 96 foods to help provide guidance on what foods may be the best to eliminate.” The tested foods are rated as Class 0-3, with Class 0 being the least reactive and Class 3 the most reactive.
They promote that their test and elimination diet can lead to an improvement in symptoms such as: “Dry and itchy skin, Other miscellaneous skin problems, Food intolerance, Feeling bloated after eating, Fatigue, Joint pain, Migraines, Headaches, Gastrointestinal (GI) distress, and Stomach pain1.”
But what exactly are they testing? What is IgG? And how is an IgG test different from MRT?
EverlyWell and MRT (Mediator Release Testing) both test for food sensitivities. Food sensitivities occur when the immune system, for whatever reason, identifies a harmless food as a threat. When a person with food sensitivities consumes a trigger food, their immune system reacts, leading to inflammation and symptoms, such as IBS, migraines, fibromyalgia, etc.
So what is IgG? IgG is an antibody, also known as an immunoglobulin (Ig). Immunoglobulins are proteins produced by the immune system for protection. There are several different classes of immunoglobulins – IgA, IgE, IgG, IgM. IgG is the most common type of immunoglobulin in your body, accounting for about 75% of immunoglobulins. IgE is the immunoglobulin class responsible for actual food allergies, like a shellfish or peanut allergy. Food sensitivities follow a different pathway than food allergies.
The EverlyWell test and MRT are not testing for food allergies (IgE). EverlyWell is testing to see if a person has elevated levels of IgG in response to exposure of a food. They are using the idea that the higher your IgG levels are to a food, the more reactive you are to that food, thus having more inflammatory symptoms – skin problems, GI issues, migraines, etc.
The problem with IgG testing is that the presence of IgG to a food does not always indicate a proinflammatory response. IgG can be elevated just because your body decided to flag a food for inspection, not necessarily because your immune system marked that food as harmful. Another role of IgG is to act as a memory or tolerance for your immune system, which means that elevated IgG can be protective and normal2.
IgG is considered a Type III Hypersensitivity. When IgG is elevated because the immune system has decided a food is harmful, IgG will then react with that food antigen and form an immune complex. That immune complex then fixes on tissues in your body where it reacts with white blood cells (WBC), such as basophils, monocytes, or neutrophils. The reaction of the IgG immune complex with WBC causes the WBC to release mediators, such as histamine, cytokines, or prostaglandins. The mediators are what cause symptoms.
IgG tests are cautioned against by: The Australian Society of Clinical Immunology and Allergy3, The European Academy of Allergy and Clinical Immunology4, The American Academy of Allergy, Asthma, and Immunology5, and the Canadian Society of Allergy and Clinical Immunology6.
Food sensitivities can follow pathways other than IgG. Another Type III Hypersensitivity Reaction is with IgM immune complexes. EverlyWell does not test IgM. There are also Type IV Hypersensitivities, which is a direct cellular reaction, and also is not tested by EverlyWell.
In Type IV Hypersensitivity Reactions, a food is taken up by antigen presenting cells and presented to T-cells for inspection7. T-cells are a type of WBC called lymphocytes. When the T-cells identity a food as harmful, they release mediators such as cytokines, histamines, and prostaglandins. The mediators then cause inflammatory symptoms such as migraines, IBS, skin issues, fibromyalgia, etc.
MRT does not measure IgG, IgM, or IgE. It is not a test for food allergies. MRT measures the release of mediators from WBC. Mediators are proinflammatory chemicals that cause inflammation in the body which leads to symptoms. MRT tests a blood sample against 170 different food and chemicals to see if WBCs release mediators and if so, how much mediator was released. The test does not look at what type of WBC reacted or what caused the WBC to react, or even what type of mediators are released. MRT is only testing the end result of a chain immune reaction to see if mediators are present8.
So if someone gets an IgG Food Sensitivity Test, they are only testing one possible mechanism for food sensitivities. And IgG can be elevated as a marker of protection. This would lead to a person unnecessarily eliminating foods and following a more restrictive diet than needed. IgG testing is higher up the immune response chain than mediators, so it’s missing other possible immune reactions.
If you’re considering getting tested for food sensitivities, do some research into exactly what type of test you’re getting and what immune mechanism is being tested. A Google search will tell you that food sensitivity testing, in general, is controversial. But if you’re suffering from migraines, fibromyalgia, IBS, or skin conditions and haven’t been able to get any answers from doctors, getting tested for food sensitivities might be worth a try.