Do Food-Sensitivity Tests Work?
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Welcome back to Food Psych Weekly, the newsletter where I answer your questions about intuitive eating, Health At Every Size, disordered-eating recovery, and how to navigate diet culture without falling into its traps.
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This week’s question is from a reader named Ronica, who writes:
What are your thoughts on the blood tests that claim that they can identify food sensitivity? I ask because elimination protocols are triggering for me, but my body is definitely reacting negatively (diarrhea & stomach pain) to something.
Thanks, Ronica, for that great question, and for your kind words. Before I answer, here’s my usual disclaimer:
These answers are for informational and educational purposes only, aren’t a substitute for individual medical or mental health advice, and don’t constitute a provider-patient relationship.
This answer will be a relatively quick and unpolished one because I’m still just getting back into the swing of things after maternity leave, but hopefully it’ll help give you some direction on this issue.
First of all, you’re not alone in wondering about these tests, or in thinking that you might have an issue with certain foods. Diet culture and wellness culture are deeply invested in making everyone think they have food sensitivities, but only a very small percentage of people truly do (as we’ll discuss in the new podcast episode coming out in a few weeks). The term food sensitivity isn’t even a true medical diagnosis, and it doesn’t have a standard definition (unlike the terms food allergy or intolerance, as in lactose intolerance and a few other conditions).
If you’re talking about the tests marketed directly to consumers for at-home food testing, those are generally bogus. They typically measure antibodies in the blood called immunoglobulin G (IgG) antibodies, which most of us have for the foods we eat regularly. In fact, IgG antibodies are considered markers of food tolerance or desensitization—they mean your body has been exposed to the food in question, and it’s totally fine with it. Even the word “antibodies” feels like a bit of a misnomer here, because these biomarkers are really “pro” food.
That’s why IgG tests often say people are supposedly sensitive to the exact same foods they eat every day—the source of much heartache for anyone who’s ever ended up with a long list of foods they’re supposed to avoid after taking one of these tests.
Some home testing kits use different technology, claiming to use your DNA to tell whether you have a food sensitivity. But the genetics of food allergy and intolerance are still very early-stage and correlational, and as we’ve discussed here many times, correlation is not causation. Just because a gene is linked to a food allergy or intolerance doesn’t mean that gene causes food sensitivity—or that the gene is even “switched on” for a particular person. So these genetic tests generally aren’t of much value in diagnosing food allergies or intolerances.
Unfortunately the problem isn’t limited to at-home food-sensitivity testing kits (which in my view should be pulled from the market). Many complementary-and-alternative-medicine providers who test for supposed food sensitivities—e.g. some chiropractors, naturopaths, functional medicine doctors, nutritionists, etc.—also use IgG testing, along with a number of other spurious tests. I’ve seen way too many people (including a number who I interviewed for my new book) harmed by bogus tests that told them to cut out a huge swath of foods and eat in incredibly restrictive ways.
Although the concept of “food sensitivity” is fuzzy and not backed up by good evidence, there are blood tests that can identify true food allergies and intolerances. These are tests you’d get by going to a physician (most likely an allergist), and they measure other antibodies in your blood that actually do predict food allergies—namely immunoglobulin E (IgE) antibodies. The same is true for serious food intolerances like celiac disease, for which IgA antibodies are the ones to measure.
OK, so we’ve established that “food sensitivity” tests probably aren’t going to give you any useful results and may well cause harm by telling you to unnecessarily restrict foods—which sounds like it would be triggering for you given your history, Ronica. Now I want to address something else I see coming up in your question, which is the assumption that food is to blame for your symptoms.
You write, “my body is definitely reacting negatively (diarrhea & stomach pain) to something.” I’m curious why you think it has to be a reaction to food, and I’d invite you to consider that the cause might not be food at all.
I obviously don’t know your full story from this short question, but given that you’ve found elimination diets triggering in the past—and that you’re writing to me now—I’d be willing to wager that you’re struggling to some extent with disordered eating. That, plus the stress of worrying about what you’re eating while living through a global pandemic and all the other chaos going on in the world for the past several years, can absolutely trigger digestive issues like diarrhea and stomach pain.
So instead of jumping to the conclusion that food is to blame—which is exactly what diet and wellness culture condition us to do—it can be helpful to look at other things that could be causing your symptoms. You might try working with an anti-diet dietitian (if that’s available to you) to help you heal from any underlying disordered eating that could be driving your digestive issues, and perhaps also a therapist to help you manage any emotional triggers. As someone with irritable bowel syndrome myself, I know all too well how stress, anxiety, and other emotions can trigger digestive issues in ways that have little or nothing to do with food (except to the extent that they mess with my appetite).
If you’ve worked on those issues for a while and are still having persistent digestive symptoms, you might seek out an allergist or gastroenterologist who can give you legitimate tests for genuine food allergies or intolerances. But I’d avoid any home testing kits, and seek out a second opinion if the physician you see starts trying to steer you toward IgG or genetic tests.
I hope that’s helpful, Ronica, and thanks again for the great question.
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Podcast Archives
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Here’s to avoiding harmful testing and unnecessarily restrictive eating,
Christy
P.S. If you want to learn more about how diet culture has influenced the health and wellness world, check out my book, Anti-Diet. It’ll help you recognize and reject the sneaky, modern guises of diet culture that pretend to be all about wellness but are actually just diets by another name, so that you can focus more of your time and energy on the things that truly matter.