Food Sensitivity Tests: Worth the Hype?
“So what you’re saying is that I’m intolerant to… everything. Great.”
This is a reaction I hear all the time from people who have undergone food sensitivity tests. Have you heard of them? Although not necessarily a novel technology, food sensitivity tests have gained recent popularity as a method to help identify and eliminate foods that someone may have a sensitivity toward in hopes of alleviating their digestive woes, migraines, fatigue, chronic pain, skin issues, and more.
The tests involve you pricking your skin to sample blood (or obtaining another type of sample), sending in your sample, and later hearing your results. The tests may be ordered by a licensed health care provider (MD, RD, etc), but there are some out there that you can order for yourself. These tests are specifically looking for food reactivities, or your body’s sensitivity to different foods, which is not the same as a food allergy. This is done by detecting levels of the Immunoglobulin G (IgG) antibody in what is considered a delayed immune response. Specifically, the tests measure how reactive your body’s IgG antibodies are to a variety of different foods. The reasoning behind this as promoted on these products’ websites is that an IgG immune response may contribute to fatigue, acne, joint pain, eczema, gut malabsorption, and other chronic conditions like IBS, migraines through chronic inflammation.
But if you’ve talked to someone who has done one of these tests, you’ll know that often times that person ends up with a laundry list of foods that they are now supposedly intolerant or sensitive toward, much to their dismay (hence the reaction above). These results are often plentiful, leading to a heavily restricted elimination diet that is stress-inducing, difficult to sustain, and confusing (like, what is actually a food sensitivity anyway?). And a lot of the foods they are “intolerant” to are super hard to avoid because they are literally in everything. To make matters worse, different brands of food sensitivity testing have been shown to provide different results. So which do you go with? And if you choose one brand over the other, are you potentially missing a food that you shouldn’t be eating? And how much do these tests cost anyway?…
So is that restrictive diet (and $200-500 cost) warranted? And are there better ways to find out what foods you may be intolerant, sensitive, or allergic to (or just don’t agree with)? I see patients who, as a result of these tests, follow such a restricted diet that I’m worried they are not getting adequate macronutrients nonetheless micronutrients. I may even have concerns over deficiencies and absolutely decreased quality of life, and even more so as these tests are conducted more and more often in pediatric patients. I’m often asked my perspective on these tests, so I’m going to share some of my thoughts and, as always, the current research.
What’s the difference between a food allergy, food intolerance, and food sensitivity?
A food allergy is a reaction that involves the immune system. In these situations, the body’s immune system sees a certain protein in a food as an invader, and produces antibodies in response (Immunoglobulin E, or IgE) to attack that certain protein. The antibodies cause an allergic reaction, which includes things like hives, swelling, and anaphylaxis. Allergists tests for food allergies in a few different ways. The gold standard is the oral food challenge, followed by serum IgE antibody testing and skin prick testing. (Quick note on IgE-mediated responses: some food allergies do not fall under this category, such as Eosinophilic Gastrointestinal Disorders and Food Protein-Induced Enterocolitis Syndrome)
On the other hand, a food intolerance involves a totally different reaction that takes place in the digestive tract and does not involve an immune system response. Food intolerances instead relate to the inability to digest specific foods due to digestive enzyme deficiencies or reactions to naturally-occurring chemicals in foods. Intolerances are also dose dependent, meaning the amount of the offending food you consume will dictate the severity of your response (which could include, bloating, nausea, abdominal pain, vomiting, diarrhea, among others). Intolerances may be diagnosed in several ways, including breath hydrogen tests or fecal tests.
Testing for autoimmune disorders that involve food, like Celiac disease, is a whole different ball game, one that I’ll save for another blog post.
Unlike allergies and intolerances, food sensitivities do not have a definition or meaning that’s accepted across the board, but generally they’re identified as some sort of food reaction that doesn’t fit in the other definitions’ criteria. Several organizations consider a food sensitivity identical to a food intolerance, while others consider it a nonspecific term that relates to any perceived reaction to food and that is up to the individual’s interpretation.
How accurate are food sensitivity tests?
As I prefaced above, food sensitivity tests measure IgG antibodies, and according to research as well as the products themselves, they do so accurately and reliably. But this is stretching the truth a bit because accuracy is not the issue. The issue lies in the fact that the production of IgG antibodies to foods is completely normal, and does not necessarily indicate a problem. An IgG reaction towards certain foods, instead, shows that the body has gone through repeated exposures to a specific food and is now recognized as a foreign protein by the immune system (again, not necessarily an invader or pathogenic). Higher levels of IgG in the blood shows that the person has eaten more of a certain food than others, as well as what foods were historically consumed. Because food-specific IgG are expected to be present in normal, healthy idnividuals, experts argue that the tests is therefore irrelevant in diagnosing food intolerances and should not be used. This sentiment is backed up by a position paper endorsed by the American Academy of Allergy, Asthma and Immunology (among other organizations), which states that using this type of testing is irrelevant for working up food allergies or intolerances and should not be used for food related complaints because food-specific IgG4 does not indicate an imminent food allergy or intolerance.
Going one step further, research shows that developing IgG or IgG4 antibodies in the body has actually been linked to developing tolerance and desensitization to different foods. So, the opposite of a food intolerance. We see this more and more in the current research as experts discuss whether or not early exposure to small doses of allergens like peanuts can help mediate the allergy as a child grows up. Really interesting stuff.
Oh, and because these tests are considered laboratory-developed tests, they are not regulated by the Food and Drug Administration. Again: not regulated. And they are not considered an FDA Approved Home and Lab Test (see for yourself here).
What about studies supporting the use of these tests?
It’s important to note that there aren’t controlled studies on the diagnostic value of IgG testing in food allergies, which provides reason for its ineffectiveness in testing for food sensitivity. Experts say that many of the studies regarding such tests for food intolerances are flawed, in that they lack a control group to make a comparison with (i.e. a controlled study), they are not randomized or blinded, measures of improvement after adopting a restricted diet are subjective rather than objective, the symptoms measured are far too broad, or foods are eliminated in different amounts between test groups. To sum it up, Robert Hamilton, a professor of medicine at Johns Hopkins University, stated in an interview “There is no firm, peer reviewed data that verifies that IgG antibody testing is diagnostically useful.” Point taken.
What about those people that say eliminating the foods from their test worked for them?
Experts also have an answer for this. First, if you think about how restrictive these diets are, it’s likely that the food that is potentially causing a patient the issue is included in the foods that are eliminated anyway. So the patient inevitably feels better but also unnecessarily eliminates a ton of foods that are beneficial and not causing issues, leading them to falsely assume that all of the eliminated foods must stay out of their diet forever.
While there are studies that show symptom improvement after changing one’s diet in accordance with test results, experts say these studies are biased due to the potential for the placebo effect. Having worked with patients who are desperate to get to the bottom of their digestive issues, one could certainly argue that finding a list of foods that they have been told are the main offenders might exert somewhat of a placebo effect because they feel like they finally have answers. Either way, it’s clear that more research with better designed studies is greatly needed in order to justify the use of these tests.
Bottom line: these tests have not been fully validated by science, and they have the potential to cause damage, including nutritional deficiencies, unintended weight loss, stress, and decreased quality of life. Furthermore, as these tests may provide false results, a patient may not avoid a food that they actually need to avoid as a result of a true allergy/intolerance, and as a result of the test may eat that food and suffer a reaction.
Part of my personal philosophy as an RD, I am not supportive of these tests obviously for the reasons I explained above, but also because I believe they support fear mongering around food. This is something we see WAY, way too often in our current health culture that is all about the newest diet and quickest way to get fit without trying. And we need to get away from it. Fear mongering and over-restricting are notions and behaviors that absolutely give way for disordered eating patterns and eating disorders, including orthorexia. It promotes obsessive thoughts and anything but a balanced diet that has room to actually enjoy food. Individuals with preexisting eating disorders or disordered eating patterns and thoughts are particularly at risk with these tests. And because we know there’s a gut-brain connection and the effect stress has on digestion, it’s entirely possible that issues such as anxiety bring about some of physical symptoms many believe are related to certain foods. Starting a very restrictive diet to help alleviate those issues may serve to only exacerbate that anxiety and thus continue to cause the issues they are trying to avoid in the first place. Think of the anxiety that can by triggered by checking every menu and label, avoiding social situations for food reasons, and stressing over the fear related to consuming “no” foods.
I do believe food sensitivities and intolerances are real, there’s no dying that. However, food sensitivity tests do not approach sensitivities or intolerances in the best way possible, in my opinion (as well as the opinion of many expert MDs and RDs in my field). The notion that a person would be intolerant to such a long list of foods is not only dangerous to one’s health, but it also promotes unnecessary restriction as well as a false hope that they have found an answer to their digestive problems in one easy test. You may ask: If these tests are bogus, what should I do to find out if I’m intolerant to something? Keep a detailed food journal for a few weeks where you document all foods, beverages, and supplements consumed (including exact brands), timing of food consumption, all symptoms, and symptom onset, duration, and severity. My advice is to review this journal with a Registered Dietitian (like myself) who is trained in working with gastrointestinal issues. Your RD will work with you to identify patterns in regards to what you consume and the symptoms you experience, and will only eliminate foods or behaviors essential for determining the offenders that bring on your symptoms. Your RD will also follow-up with you (unlike these tests) to continue to monitor and evaluate your diet and manage any necessary changes. I am a huge proponent of finding the least restrictive diet possible for each individual to maximize nutrient intake and prevent nutritional deficiencies and at worst, malnutrition, and I don’t believe you should settle for anything else either.
If you’ve undergone a food sensitivity test, I want to know! What were your experiences, did you find symptom relief, do you feel you are able to maintain the restrictive diet? I’d love to know your opinions here!
A quick note: If you feel you have a true food allergy, it’s important to see a doctor/allergist for a diagnosis and eliminate any offending foods as needed.