Many people seek out my clinic wondering if their intestinal symptoms are related to food allergies. They want to know if they should be avoiding certain foods to improve their health or help treat certain diseases. Food allergies and food intolerances can be a confusing topic, and this article is designed to help you understand the difference between allergic food reactions and food sensitivities (aka intolerances) and whether you might benefit from food sensitivity testing.

To understand this topic, it is helpful to understand a little about our IgA, IgE, and IgG immune responses. IgA, IgG and IgE refer to immunoglobulins (aka antibodies). These antibodies are our immune system’s response to things we come into contact with on a daily basis. Our bodies make antibodies to foreign substances like bacteria and viruses, but antibodies can also respond to foods, dust, dander, and pollen.

IgA and IgG reactions are known as delayed hypersensitivity reactions, while IgE responses are immediate and are considered a true food allergy. IgA and IgG reactions often do not happen immediately, but instead develop between 2-24 hours after eating a particular food. They can cause a great variety of symptoms including rashes like eczema or psoriasis, headaches, fatigue, brain fog, joint pain, as well as numerous intestinal symptoms. The most common GI symptoms people can experience with an IgA or IgG reaction are reflux, gas, bloating, abdominal pain, constipation and/or diarrhea.

IgE Antibodies:

IgE allergic reactions often present with symptoms like hives, itching of the mouth, and throat swelling. Other symptoms can include wheezing, coughing, a runny nose, vomiting, swelling of the lips or tongue, or even a weak pulse and loss of consciousness if the allergy is severe (anaphylaxis). While it is possible to have intestinal symptoms with an IgE allergy, this is less common.

IgA Antibodies:

IgA immunoglobulins are present in organs lined with mucus membranes. This includes your mouth, throat, stomach, intestines, and urinary tract. IgA antibodies increase when the foods we eat cause inflammation, and these antibodies can also respond to stress, infectious disease, or alcohol.

IgG Antibodies:

An IgG reaction to food proteins can suggest a variety of scenarios. Low IgG elevations may simply mean that a person has a tolerance to that food due to regular exposures. But higher IgG reposes can indicate inflammation and immune reactivity to a particular food throughout the body.

Testing for Food Allergies and Intolerances:

You can test for IgE allergic reactions with skin prick or patch testing as well as through blood testing. IgA and IgG reactions to foods can be tested in the blood as well, though there is some controversy of the accuracy of this testing. This is why insurance typically covers IgE testing but not IgA and IgG analysis. Part of the controversy is due to the fact that not all labs that offer IgG and IgA tests produce reproducible results (i.e. the same person given the test multiple times recieves different results). Additionally, the IgG molecule likely has more than one function in the body, and science is still figuring out the complexity of different types of IgG reactions in the body.

As a naturopathic practitioner, I have had experience with laboratories that provide results that are both reproducible and also correlate with patient symptoms, and I have also seen other labs that did not. Therefore, the quality of the lab is of upmost importance for patients considering food intolerance testing. The lab I work with is US Biotek, though there are other reputable labs as well.

While food intolerance testing can be incredibly helpful in identifying which foods may be causing uncomfortable symptoms and underlying many disease processes, I agree that the science in this area is not 100%. For this reason, I typically advise an experimental/therapeutic elimination diet for patients once testing has been completed. We remove all foods with higher than a mild IgG or IgA elevation according to their lab results, and the patient remains on this diet for six weeks. At that time, we have a follow up and discuss which symptoms improved or didn’t improve. At that point, I have the patient eat one food at a time off of their intolerance list to test for a reaction. I typically advise that they eat one serving of that food twice a day for two days in a row to significantly challenge their system. If the patient has any return in symptoms, then this food is likely a long-term intolerance and should be avoided. If no reaction, then it is likely that this food is not actually causing inflammation and can be added back into the diet.

This re-trial of eliminated foods is equally if not more important than the removal part of the diet. After this period of elimination and re-trial has been completed, patients usually have a great degree of clarity about which foods actually are worsening their health and which foods they are free to eat without worry. That is probably the thing I like most about this testing: it gives patients such confidence to learn how to listen to their bodies and learn how to interpret symptoms to take care of their own health. It can be difficult to trust symptoms before the testing/elimination period because often patients are eating multiple intolerances at once and their reactions are blurred together.

While it is possible to get these results from a more traditional elimination diet, I much prefer food intolerance testing as it typically gives us clarity much faster and also helps patients avoid having to drastically limit the diet for long periods of time. Often with elimination diets (which remove almost everything from the diet besides meat and vegetables), patients give up before completing the elimination/retrial period because they find the diet too restrictive.

Dr. Katie Nuckolls is a naturopathic physician and owner of Thrive GI: Natural Digestive Medicine in Vancouver, Washington. She currently sees patients that live in Washington, Oregon, and Arizona using telemedicine. For more information, visit our contact page or schedule a free 15-minute consultation online.  

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