By: Dr. Dominique Vanier ND

Food Sensitivity Testing is a popular blood test that tests for sensitivities to food. It does this by looking at specific IgG antibodies in the blood to a wide range of foods, like dairy products, gluten and gluten-free grains, veggies, fruits, and animal proteins.

I see many patients who have reactions to various foods, symptoms like bloating, abdominal gas, pain, burping, and changes to bowel movements like diarrhea and constipation. Many of these patients have already cut out some foods from their diet, such as gluten or dairy, before seeing me in an appointment in an attempt to investigate if food elimination makes a difference in their digestion.

Often at this point in their journey, patients come to their first appointment requesting food sensitivity testing. It’s my role to educate patients on food sensitivity testing and other options so they can make the most informed choice that is best for them.

Food sensitivity testing has some pros. It is a quick and easy blood test that summarizes foods in ‘red’, ‘yellow’, and ‘green’ categories. The idea is that it may help take some of the guess work out of identifying ‘trigger foods’. The foods categorized as red and yellow are the ones that a patient has high or medium sensitivity to. They are removed from the diet for 4-6 weeks, then reintroduced to determine which ones someone is truly sensitive to.

For some individuals, this test can be tremendously helpful. However, there is some faulty logic with the food sensitivity testing approach in general. The larger, more important issue regarding food sensitivity testing is that the digestive system shouldn’t be sensitive to foods in the first place. This is a hallmark symptom of irritable bowel syndrome (IBS) and other functional digestive disorders, and is also common in inflammatory bowel disease and in unmanaged Celiac disease. ‘Cutting all the foods’ may help in the short-term to alleviate some symptoms, but is not a long-term strategy. The diversity and function of the gut microbiome is dependent on a wide variety of foods in the diet, in particular dietary fibre. There is also evidence that a restricted diet over the long-term can, in fact, worsen digestive symptoms — in essence, making the food sensitivity test obsolete.

There are also questions about the validity of IgG antibodies as a marker of food sensitivities. Rather than indicating a food sensitivity, IgG antibodies may actually show that a person is tolerant of the food, or in other words, has been exposed to the food. This means the test likely has many false positives and makes it confusing to hone in on which foods are truly causing a sensitivity.

Cutting out all the food sensitivities may also lead to an overly restrictive diet. And in the population of people with IBS and other disorders of the brain-gut connection, research has shown that restrictive dietary practices can progress and increase risk for development of disordered eating patterns

This is why it is imperative that patients with digestive challenges work with a skilled gut practitioner who has experience in swiftly identifying food sensitivities while providing a plan for both food reintroduction and gut microbiome modulation and support. As an evidence-based practitioner, I regularly recommend a short-term (i.e., two- to six-week) implementation of the low-FODMAP diet with a plan to reintroduce foods and identify which foods remain as trigger foods, and using other supportive approaches like prebiotics and probiotics. The low-FODMAP diet has over 380 research papers and 50 clinical trials to support its use and utility. In contrast to the food sensitivity test, there is little-to-no research supporting IgG food sensitivity testing (and it is costly!).