Wow! I've heard far too many stories from clients, friends and strangers that they have erroneously invested in these "diagnostic tests" and ended up no more healthier, if not left worse off than before taking the test... My point I'm going to get across is clear from the title of this post, because I just can't stand to see another poor soul sucked into the expensive black hole of IgG-mediated food intolerance testing.
Below I list the pros (few) and cons (many) of a specific kind of food intolerance test sold in many drugstores in Canada, by a number of naturopaths, and even some other health professionals who teach nutrition.
Food allergies are reaction to food proteins. There are a few different types:
Immunoglobulin E (IgE)–mediated (immediate) reactions
Non–IgE-mediated (delayed) hypersensitivity reactions
Mixed reactions (both IgE and non-IgE at the same time)
IgE-mediated reactions are the ones we worry about when we hear about a “food allergy”: flushing, itchy skin, wheezing, vomiting, throat swelling, and even anaphylaxis. These reactions can occur immediately following exposure, and are the result of the interaction of allergens with IgE located on mast cells. The interaction causes the release of inflammatory chemicals like histamine and leucotriene, triggering the allergic response which is typically skin related (itchiness, swelling and rash) but may be anaphylactic as well.
Not all reactions follow this cascade. Non-IgE-mediated allergic reactions can cause localized (e.g., contact dermatitis) or generalized reactions, which are usually gastrointestinal or dermatological in nature. Celiac disease is a non-IgE related allergic reaction.
Finally, some allergic disorders are both IgE and non-IgE mediated, such as atopic dermatitis (eczema).
Beyond the IgE mediated reactions, there are a number of possible reactions to food, which may be termed “food intolerances”. They are not immune-system based, and they are more common than allergies. They include conditions like lactose intolerance, gastroesophageal reflux (GERD), enzyme deficiencies, metabolic conditions, infections and other processes. It’s a catch-all term by definition.
So what about IgG food intolerance testing?
IgG-mediated food intolerance testing goes by various brand names according to the company that is trying to sell you a testing kit. You'd provide a blood sample and receive a lengthy list of what you should and should not eat. IgG antibodies are molecules that mediate interactions of cells with different cellular mechanisms. IgG antibodies signify exposure to products—not allergy.
To make that clear, IgG antibodies may actually be a marker for food tolerance, not intolerance! Some research suggests children with eczema and egg or milk allergies with higher levels of IgG to milk/egg were more likely to be tolerant of these foods at a later age. The same has been found for peanut allergies - that IgG levels rise as tolerance to peanuts increases. Also, a study found increasing IgG in patients who underwent oral immunotherapy for milk or peanut allergy. Given the lack of correlation between the presence of IgG and physical manifestations of illness or symptoms, IgG testing is considered unproven as a diagnostic agent as the results lack clinical utility as a tool for dietary modification or food elimination. Furthermore, serum (blood) IgG levels do NOT respond to oral challenges, unlike IgE levels, which indicate an allergic reaction.
I'll cite a few credible associations and internationally-recognized papers here:
"IgG and IgG subclass antibody tests for food allergy do not have clinical relevance, are not validated, lack sufficient quality control, and should not be performed." - the American Academy of Allergy, Asthma and Immunology & American College of Allergy, Asthma and Immunology.
"Testing for blood IgG4 against different foods is performed with large-scale screening for hundreds of food items by enzyme—linked immunosorbent assay-type and radioallergosorbent-type assays in young children, adolescents and adults. However, many serum samples show positive IgG4 results without corresponding clinical symptoms. These findings, combined with the lack of convincing evidence for histamine-releasing properties of IgG4 in humans, and lack of any controlled studies on the diagnostic value of IgG4 testing in food allergy, do not provide any basis for the hypothesis that food-specific IgG4 should be attributed with an effector role in food hypersensitivity." - the European Academy of Allergy and Clinical Immunology.
"IgG antibodies to food are commonly detectable in healthy adult patients and children, independent of the presence of absence of food-related symptoms. There is no credible evidence that measuring IgG antibodies is useful for diagnosing food allergy or intolerance, nor that IgG antibodies cause symptoms. In fact, IgG antibodies reflect exposure to allergen but not the presence of disease." - the Australasian Society of Clinical Immunology and Allergy (ASCIA)
IgG testing is advertised as an indicator of "delayed reaction" to food, though there is no evidence to back this up. Often, a person who takes this test is left confused as to what a healthy diet looks like for themselves, and ends up eliminating a number of healthy foods which may lead to nutritional deficiencies of protein, carbohydrates, fats, or vitamins and minerals. Some of them end up in my office, seeking answers and wanting to take on their health concerns with the help of a credible professional, the sustainable way!
I rest my case.
Please share with your friends and family and spread the news! You never know who is about to waste $200 + on these kinds of things... Knowledge is power!
Wondering about how you can apply one of these tests to healthy eating if you've already got one done? Got questions about possible food intolerances and symptoms that you can't quite figure out?
Send me a quick message about your concerns and I'd be happy to help!