“But where’s the harm?” we are so often asked. When your baby dies and has to be resuscitated in the emergency room, I’d say the harm has a Vegas-sized neon arrow above it.
An infant boy in Hong Kong had a really bad reaction to being introduced to cow’s milk at eight months of age: vomiting, difficulty breathing, and a generalized skin rash. The doctors performed an allergy test by pricking his skin and sure enough the boy was allergic to a protein in cow’s milk. Hurray for modern science.
But the boy’s mom heard about a treatment that could reverse this allergy. The problem? The treatment was homeopathic. We have covered homeopathyĚýmanyĚýtimesĚýhere: basically, an alternative to medicine propped up by nonsensical dilutions and a belief in sympathetic magic, homeopathy does not work and cannot work. Indeed, in this case, it likewise did not work, but itĚýappearedĚýto work. Why? Because of a confusing IgG test.
These tests evaluate your blood for a variety of food items you might be intolerant to. The subsequent report tells you which foods to reduce or eliminate from your diet to improve your symptoms. The IgG test told the mom that her son wasĚýnotĚýsensitive to cow’s milk, so she gave him some. That’s when the boy had to be brought to the emergency room and resuscitated.
I know about this because doctors from that hospital took the time to write up thisĚýĚýand publish it in the medical literature. Their larger point is that these IgG food intolerance tests have not been shown to work and their results can lead to serious problems. And they are far from the only ones to warn potential customers away from these dubious and expensive tests.
The above story also illustrates how easily people will confuse a foodĚýallergyĚýwith a foodĚýintolerance. They are two very different things.
An allergy directly involves our immune system, whereas an intolerance does not. The symptoms of a food allergy are due to parts of our immune system mistakenly thinking it needs to attack something otherwise innocuous, like a peanut, and this unwarranted response can put our life in danger. Food allergies come in three types, revolving around a molecule called IgE, which is short for immunoglobulin E. For our purposes, I will say that the words “immunoglobulin” and “antibody” are essentially synonymous. IgE is thus an antibody produced by the immune system and it will trigger that immediate allergic reaction you think of when imagining someone with a peanut allergy accidentally ingesting that legume and feeling their throat closing up.
At the molecular level, what is happening is simple: a protein found in that peanut binds to that Y-shaped immunoglobulin E antibody sticking out at the surface of a mast cell, which is a specialized type of white blood cells. That contact forces the mast cell to release histamine and other inflammatory molecules. The result is redness, swelling, and, in some cases, death. By the way, this is the same principle at work when an allergist pricks your skin to see what you are allergic to. Those needles are coated in the protein of a particular item that can trigger allergies, and the protein will either bind to the IgE at the surface of your mast cells or not.
Delayed allergic reactions are not linked to IgE, however, and some allergic reactions are a mixture of the two. But food intolerance tests do not look at IgE; they evaluate a response by IgG, a different immunoglobulin.
IgG food intolerance tests will expose your blood in the laboratory to a panel of foods and food components. The degree to which immunoglobulin G in your blood binds to each item is then quantified using a technique known as an immunosorbent assay. Some tests will instead focus on a subset of immunoglobulin G called IgG4, but the principle is identical. An intolerance is not driven by an immune reaction, however, despite the use of IgG in these tests. Intolerances are blurry entities. They are difficulties in digesting or metabolizing certain foods. A prime example is lactose intolerance. With a dairy allergy, the immune system reacts to a protein in milk and figuratively loses its mind; with a lactose intolerance, it’s just that the gut makes too little of a pair of molecular scissors that are needed to cut the milk sugar lactose into the smaller sugars glucose and galactose. The undigested lactose ends up in the colon, where bacteria feast on it and release gas, creating bloating. Hence, no primary involvement of the immune system here.
But the laboratories selling you these tests would have you believe that IgG is somehow involved in this intolerance, and that the more binding there is between IgG and the food, the more intolerant you are, in the same way that IgE prick tests work for allergies. And these IgG tests are not cheap. Companies are now cagey about pricing on their websites, but past investigations have revealed price tags in the hundreds of dollars.
You can wade through the scientific literature and you will see studies that seem to give credence to these tests. One of them, authored by Marinkovich andĚý, has beenĚýĚýon numerous points: no randomization, no blinding, and ill-defined, subjective measurements. AĚýĚýprovided evidence that excluding food based on an IgG test improves the quality of life of people living with ulcerative colitis, a type of inflammatory bowel disease. But here’s the catch: they were compared to people with the disease who didn’t change their diet at all. It’s quite possible that thereĚýwasĚýa trigger in their diet, but it does not imply that IgG tests are useful. You can imagine a person’s colitis being triggered by, let’s say, peanuts, and an IgG test telling them they have to remove 25 ingredients from their diet, including peanuts. They will feel better, but they will be severely limiting their diet for no good reason.
You may think I’m exaggerating when I say that an IgG test could tell you to eliminate 25 ingredients from your diet, but I’m not. AĚýĚýof these tests revealed that one person was told to eliminateĚý26Ěýof them, including wheat, milk, eggs, corn, potatoes, and peanuts. The host of the show sent her blood to two companies offering these tests: one reported 30 intolerances, while the other flagged 52. Putting aside the lack of agreement between the companies, many of these food items were regularly consumed by the host with no symptom whatsoever.
These tests are so unreliable that a long list of professional orders and associations have denounced them—a kind of unity that I rarely see, as these societies tend to shy away from condemning pseudoscience. Yet, the Canadian Society of Allergy and Clinical ImmunologyĚýĚýthis practice. The American Academy of Allergy, Asthma & Immunology calls the test aĚýĚýand recommends against using it. As rounded up by pharmacist Scott Gavura forĚý, many more such organizations have published similar statements, and searching for IgG food intolerance tests on Google now will reveal many warnings in between the webpages of laboratories offering this dubious test.
So what are these laboratories detecting, then? Ironically, it’s probablyĚýtoleranceĚýto food, not intolerance.ĚýĚýof theĚýĚýexplain the presence of IgG as healthy, a sign that your immune system has seen this food item pass by and is metaphorically tipping its hat in its direction. Hence, withholding food items in a baby because an IgG test calls out an intolerance could be problem: not only is the diet getting unnecessarily restrictive, it couldĚýĚýthat did not exist in the first place.
In short, these IgG tests have a lot to answer for.
And if you don’t want to believe medical professionals on this because your naturopath has prescribed one of these tests to you, let’s look at people associated with so-called alternative medicine. Many do recommend these tests, but others don’t. Dr. Randy Horwitz, from the Andrew Weil Center for Integrative Medicine, is one of the authors on aĚýĚýcriticizingĚýthese food intolerance tests. And way back in 1998, authors from the Royal London Homeopathic Hospital and from the Research Council for Complementary Medicine were revealing the results of their ownĚý, which would be echoed by CBC Marketplace twenty years later.
Nine months after using the test within the hospital, strange findings made their way to an audit group. Patients were testing positive for food they had never eaten, while also testing negative for items they knew triggered their intolerance. The hospital took duplicate blood samples from 9 patients and sent them out to the one lab they had contracted for this test: for each patient, one sample was in their name, the other in a fictional name. The results were abysmal, with low reliability. In one patient, 50 of the 95 foods tested for IgG binding were inconsistent between the first and second blood samples.
The audit group recommended the IgG food intolerance test be discontinued.
If this test were indeed reliable, dietitians and allergists would gladly charge you for it. But just because a test involves scientific words and techniques does not mean it’s accurate or even scientifically plausible.
Food intolerances can’t be determined via IgG test,Ěý. They require, funnily enough given the kinds of therapists who typically order them, a more holistic approach: patient history, physical examination, and a short-term elimination diet followed by a reintroduction of the likely suspect under the supervision of a qualified dietitian.
It may be time consumers develop an intolerance to IgG food intolerance tests.
Take-home message:
- A food allergy is caused by a reaction of the immune system, whereas a food intolerance represents a difficulty digesting or metabolizing a food item
- IgG food intolerance tests are claimed to diagnose which foods you are intolerant to, but they are wildly inaccurate and have been denounced by major professional organizations
- Studies indicate that the presence in the blood of IgG antibodies against a certain food item may actually be a marker of tolerance to the food, not intolerance
