Food Sensitivity Testing
Updated: May 2019
Tests provide specific “answers,” which gives patients hope and control. Unfortunately, every test gives a different answer.
Each company claims their test is the right one, and the others are wrong. I would love to have a valid test that would accurately pinpoint my clients’ food triggers. It would be wonderful to give clients definitive answers and make exact meal plans for them. As an evidence-based health professional, I cannot recommend food sensitivity testing to my clients just because it will make my job easier.
Why does testing often lead to symptom improvement?
There are several reasons why symptoms may improve following a diet based on a non-validated testing method.
- Treatment and placebo effect: Patients often feel better when starting new treatments, because there is a sense of hope.
- Restricting common food triggers: Most testing methods will pinpoint several foods, including common food triggers, such as gluten, milk, tomatoes, etc. If a person is sensitive to gluten, and they get a list of 25 foods to avoid (including gluten), their symptoms would improve because of the gluten restriction, not the other 24 foods.
- Natural fluctuations: Symptoms tend to get better and worse for unknown reasons. People usually seek treatment when their symptoms are bad, and they may have naturally improved without any treatment.
- Healthier Diet: Typically, people have poor diets – skipping meals, processed foods, etc. These habits often improve when they start a new diet plan. The healthier diet, not the restriction, may be the reason for symptom improvement.
Valid laboratory tests
Useful laboratory tests are developed over many years of careful research. The process starts with understanding the pathology of a disease and figuring out what compound could be measured to detect the disease. Research is needed to see if this theory works. In most cases, several universities conduct research and publish their findings in peer reviewed journals, allowing university researchers to learn from each other and develop a strong body of knowledge. Over time, a consensus is hopefully reached about the precise technique to conduct the test and interpret the results. In many cases, the research does not support the theory and the test is not used in clinical practice.
Companies convince patients and practitioners their tests are valid
With clever marketing, companies can make their unresearched tests sound valid. Unfortunately, there are no regulations. The terms “accredited lab” or “awarded patents” are business terms and have no relation to research. Companies will often list several research articles on their website, but the research does not have much to do with the actual test (see examples below). In other cases, the company will list the research that loosely supports their testing method, but completely ignore the research that does not. Finally, companies often report open or non-blinded studies. People usually feel better when they start a new treatment, regardless of the effectiveness of that treatment (placebo effect). Good research studies include a placebo group to counteract this. The treatment is successful if the subjects in the treatment group improve more than the subjects in the placebo group. Open or non-blinded studies only have one group – the treatment group. The results are not meaningful. When companies report this information, it is a “group testimonial,” not a real study.
Why don’t companies validate their tests?
Companies can make a lot of money without the effort of doing research, and a proper research study would probably not support their test. I’m often approached by companies to promote their food sensitivity testing to my clients and colleagues. When I ask companies to provide published research, they usually say that research is too expensive. A basic research study would be inexpensive. People with a certain condition or symptom(s) could be divided into two groups. One group would get their own food sensitivity testing results, and the other group’s results would be mixed up (a subject would get someone else’s results). If the first group, improves significantly more than the second group, there would be objective evidence that the testing method is helpful. I would be happy to promote a testing method if a company could provide any objective evidence that it works.
Different Testing Methods
I’ve listed some brief information about common tests below.
When a patient reports immediate allergy symptoms after eating a specific food, the physician will likely use blood or skin tests to determine if the patient’s immune system is producing IgE to that food. These tests are important tools to help diagnose IgE food allergy. Unfortunately, panel tests that include several foods are often used. The high rate of false positives often leads to unnecessary dietary restrictions. See IgE Food Allergies (subheading – IgE Food Allergy Diagnosis) for more details.
IgG is a different antibody than IgE. Patients can access food specific IgG testing through a health professional or directly from a lab (the lab will send a special cardboard that the patient drops blood on and mails back). IgG testing has been popular for many decades. Fairly recently, several research studies have shown it to be ineffective. In fact, IgG4 increases with food tolerance (which is the exact opposite of the theory of this testing). Despite the recent studies, the popularity continues. See above: Companies Convince Patients and Practitioners Their Tests are Valid.
A few years ago, I was doing some research for a presentation at the Dietitians of Canada conference. I talked with the chief chemist at a large lab that ran combined IgE/IgG blood testing. I was expecting an argument when I said that this test does not make sense, but the chemist agreed with me and said that they have been using the same technology for over 40 years! Antibody testing has progressed over the last few decades. Forty-year-old technology is no longer valid. When I asked why they are still selling this test, she responded with, “It is very popular with practitioners.” In other words, they’re making money.
Furthermore, the technique to measure IgG is not standardized. If the same blood sample was sent to different laboratories, the results would be different. I called several laboratories during my research, and each laboratory said they had the right technique, and the other laboratories were wrong.
This testing is part of the LEAP program. The theory is based on the science of immunology, so it sounds impressive and is very appealing to people with mast cell activation (because tests mediator release). The home page states that MRT is the gold standard for food sensitivity testing and anti-inflammatory eating. Here’s a screen capture from the home page on June 17, 2015. In the research section of the company’s website, I found general articles on immunology, but nothing about the testing method. I contacted the company and asked for the research to support their claims about the University of Miami. The company sent two newsletter articles with testimonials from doctors. When I asked specifically for well conducted research, I did not hear back.
This test measures a combination of IgG4 and IgE to a variety of foods. Research clearly shows that as IgE decreases, IgG4 increases – so it does not make sense to combine the results.
Moreover, the sample report on the website states:
Basically, the company is admitting that a negative result is not accurate. Food specific IgE has very low rates of false negatives. When combined with IgG4, it is no longer valid.
2 Responses
Good morning Wendy, I’m so glad I found your site. It’s wonderful and so helpful. I’ve been told to adhere to a Low FODMAP diet as well as a low histamine diet. Do you know of an app that tells you if foods are both low histamine and Low FODMAP. It’s quite difficult figuring out what to eat and what not to eat. Any help would be greatly appreciate it. Thank you in advance!
Please let me know if you have any questions.