Food allergies and intolerances are an interesting beast and to be honest, the whole topic is confusing. Part of the problem is that there is a lot of misinformation out there when it comes to food allergies and sensitivities, including controversy over their existence.
I decided to tackle this topic due to an influx of clients coming in with “ food allergy” or “food sensitivity” blood test results, panicking over what to eat given their new, long list of ‘off limit’ foods. What I find most interesting and also frustrating about this scenario is when asking clients if they’ve been symptomatic to these foods, or if they’ve been feeling better/different since eliminating them, the answer is typically “no”.
So the question is, if you’re not feeling sick eating them, is there any good reason to eliminate them?
The blood test in question measures specific IgGs (immunoglobulin G or IgG antibody). You may have heard of them or maybe have even been sucked into the trap! Don’t be ashamed, I would be too, as the promises sound awesome, and unless you’re an immunologist, it also sounds pretty scientifically legit.
Advertisements for this test lead patients to believe that the test will help them diagnose their food allergies and sensitivities. There’s a plethora of reasons why people are enticed by these tests. Frustration with bothersome health symptoms is common. In some cases, people are genuinely trying to get to the bottom of what they think is a food intolerance and hoping for some more concrete clues. Rightly so! Not only do these tests claim to diagnose food sensitivities, but I’ve also heard claims that the results will lead to weight loss, resolution of chronic fatigue, skin problems, GI upset, and my favourite; generalized ‘inflammation’. I have yet to find any client that actually knows quite what that means, but it sure sounds important.
Unfortunately, these tests are not scientifically sound, not administered by medical practitioners, and can cost anywhere from $400-$700. They are definitely not covered by OHIP.
The truth is, these IgG antibodies are found in normal, healthy people WITHOUT any food sensitivities. And, those with serious food allergies may have low or undetectable levels of food specific IgG. Yikes.
Dr. Lauren Segal, a Board Certified Allergist and Clinical Immunologist, practicing in Ottawa, Ontario contributed to this article and was happy to help me set the record straight about this topic. She too is frustrated by these inordinately expensive tests as they are invalidated, and pose a risk to patients, taking advantage of people looking for answers. Dr. Segal described this scenario: A patient who is severely allergic to a food, say peanuts, gets a result back saying that he/she has very low levels of peanut specific IgG. This is because serum IgGs are the wrong test to diagnose food allergies. Food allergies are when the immune system ‘overreacts’ to proteins in foods, causing the release of inflammatory chemicals and can result in skin rashes, swelling, itching, wheezing, and even anaphylaxis. They are diagnosed by history and confirmatory skin prick testing or a blood test measuring serum specific IgE (immune globulin E, a different type than IgG). In this case, the misleadingly low IgG may incorrectly suggest to the patient that he or she could safely eat peanuts - putting them at great risk if consumed.
Dr. Segal says that many not-for-profit medical organizations that advocate for patients and evidence based practices have actually come out with strong position statements against the use of food specific IgG testing. One such organization is The Canadian Society of Allergy and Clinical Immunology, an organization composed of the majority of Canada’s allergists. Their statement discouraging specific IgG testing can be found here: https://aacijournal.biomedcentral.com/articles/10.1186/1710-1492-8-12
While food intolerances and food sensitivities are NOT allergies, they ARE a huge nuisance. Although there’s not a whole lot of good evidence or diagnostic procedures for them, they can affect the quality of peoples lives, often leading to symptoms like bloating, gas, lack of energy, pooping problems, and more. They are difficult to diagnose because so many conditions present similarly, including poor diet, stress, food borne illness, reflux, IBS, and the list goes on. Celiac disease, incidentally is not an allergy or a sensitivity, but classified as autoimmune disease that can be confirmed through IgA (yet another type of immune globulin) blood test and endoscopy, (as long as gluten has not yet been eliminated). Some of the more common food intolerances include gluten and lactose (the sugar found in milk). Lactose intolerance can be tested for with a specific lactose tolerance test. Gluten intolerance, although still only a nebulously defined entity, and other suspected food intolerances are still best diagnosed by the good ol' elimination diet. Done properly, with the right re-introduction techniques this remains the most conclusive and evidence-based method for diagnosing ANY food sensitivity or intolerance. None of these techniques rely on IgG testing.
Given the complexity and challenges of diagnosing both food allergies, and food intolerances, it’s always a good idea to track symptoms and patterns and see your family doctor. If appropriate, a referral to a gastroenterologist or allergist will help to determine the best course of action, and a dietitian may also be able to help guide you in making safe food choices, meeting nutritional needs, and with symptom recognition.
Bottom line: If you or someone you know is offered the IgG food sensitivity test, JUST SAY NO!