When I was first introduced to the underlying concepts of Functional Medicine, I was a proponent of IgG based Food Sensitivity Tests. I mean, why wouldn’t I be? It made my job exponentially easier. Allergic Rhinitis, GI disorders, brain fog, and migraines could all be chalked up to food sensitivities and a basic elimination diet was the elixir. I was completely oblivious.
For clarity’s sake, let’s start by discussing the difference between an Allergy, Intolerance, and “Sensitivity”. These terms are often used interchangeably, and it is imperative to understand that there is a significant difference between these terms. Food Allergies are a result of an immune mediated response to food and can be extremely dangerous. A Food Intolerance on the other hand is the bodies inability to process food.
These tests that claim to accurately diagnose food sensitivities are the food IgG test. This test is available to consumer through multiple lab companies and claim that the removal of IgG foods is a cure for all health ailments. Some Food Sensitivity companies even report that utilizing these tests can help treat irritable bowel syndrome, autism, cystic fibrosis, rheumatoid arthritis and epilepsy.
There is very little literature supporting the use of IgG food sensitivity testing and the few research papers I found were outdated and not peer reviewed. That is why both the American Academy of Allergy, Asthma and Immunology as well as the European Academy of Allergy and Clinical Immunology found that there was an overwhelming lack of evidence to support the use of IgG Food Sensitivity tests in clinical practice and that IgG based reactions were likely attributable to a normal physiological response.
So why then do some individuals feel better on IgG Elimination Diets? Outside of a strong placebo effect patients will usually see some improvement on an Elimination Diet, especially when taking out things like Wheat, Diary, Eggs, Nuts, and Fish-which are all common food allergies. Stricter glycemic control and possibly incorporating more phytonutrient dense food into the diet may also contribute.
About a year ago I started challenging some of the science behind the foundations of a Functional Medicine approach including the fallacious notions of Adrenal Fatigue, Heavy Metal Toxicity, and most importantly-IgG Food Sensitivity Testing. The overwhelming lack of evidence to support tests like this were frustrating for a new provider and for patients who had spent north of a thousand dollars for tests that have negligible clinical utility.
Dr. Tanner Wilson, DC, IFMCP is a Functional Medicine Doctor in Kansas that specializes in the treatment of Chronic Disease.