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Why Food Sensitivity Tests Are Dangerous for Kids
These popular tests are not backed by science, and they have serious downsides. Plus: Five other tests to avoid.
Welcome to a very special edition of Is My Kid the Asshole. Today we’re talking about food sensitivity tests, which I started digging into several months ago after almost ordering one for my daughter. I was pretty shocked by what I discovered and wound up discussing the tests with my dear friend and amazing anti-diet journalist , who writes . As it turned out, she had also been researching these tests and the insidious ways they are marketed to moms — so we decided to team up to tackle the issue. Head over to Burnt Toast today to read her excellent companion piece.
Why Food Sensitivity Tests Are Dangerous for Kids
A year ago, my now 9-year-old daughter started complaining of frequent stomachaches. She’d had the odd belly woe here and there throughout her life — certainly more than my son ever had — and they’d always concerned me in a low-level way, but suddenly they seemed to be ramping up. Was it constipation? Reflux? Maybe a food allergy or intolerance?
The CDC reports that the prevalence of food allergies — which occur when the body’s immune system overreacts to a component of food — increased by 50 percent between 1997 and 2011. Food intolerances, which happen when the digestive system is unable to digest certain foods, also appear to be exceptionally common. According to one survey, as many as a quarter of U.S. adults report suffering from one.
I wondered what to do about my daughter. I considered having her cut out a common culprit — maybe gluten — to see if that would help. I researched pediatric gastroenterologists. I also stumbled across food sensitivity tests I could buy online that promised to identify the specific foods that might be causing her symptoms. Those seemed extremely appealing — far faster and easier, it seemed, than keeping a food diary to try to identify potential culprits over time.
To my immense relief, before I settled on a decision, my daughter’s stomachaches eased. And, thankfully, they haven’t come back. Even so, I decided to dig into the issue of food sensitivity, as well as the tests that claim to diagnose them. Today I’m sharing what I’ve found, because it is, honestly, shocking and concerning. It’s yet another example of science being misconstrued to mislead and make money off of parents, which is why I’m covering it: My goal in writing this newsletter is to shed light on insidious parenting messages and trends. These tests are especially worrisome because the decisions parents make based on their results can actually make their kids sick, as I’ll explain.
Indeed, food sensitivity tests are heavily marketed to women and mothers, as Virginia explains in her companion piece. (One, by YorkTest, is specifically for kids.) You may have seen the tests recommended on Shark Tank or on Instagram. Some naturopaths and integrative medicine physicians rely heavily on them. These tests claim “to identify foods in your current diet that might be connected to food sensitivity symptoms,” which might include abdominal pain, bloating, headache or indigestion.
And yet, when you look at the science, you discover that these tests can actually do none of these things. “It's all made-up mumbo jumbo,” said Dr. David Stukus, a pediatric allergy specialist at Nationwide Children’s Hospital in Ohio. The American Academy of Allergy, Asthma and Immunology, the European Academy of Allergy and Clinical Immunology, and Canadian Society of Allergy and Clinical Immunology all warn against the use of these tests.
Why these tests don’t work
First of all, “food sensitivity” isn’t even a real clinical phenomenon, unlike “food allergy” or “food intolerance,” both of which are.
“There is no consensus medical definition or diagnostic criteria for ‘food sensitivity,’ which is why it can be applied to pretty anything someone wants to make up,” Dr. Stukus told me.
Tests that claim to diagnose sensitivities measure blood levels of an antibody called immunoglobulin G, or IgG, which the body produces after being exposed to components of food. All foods interact with our immune system, and over time, our bodies create “immune memories” based on these interactions, explained Dr. Elana Lavine, a pediatric allergist and immunologist in Toronto. IgG antibodies are evidence that those memories have been formed — that our bodies have gotten to know and remember a particular food.
Food sensitivity tests are based on the incorrect notion that high levels of IgG in response to a food indicate that a person is sensitive to that particular food and perhaps shouldn’t eat it — but in fact, IgG is merely a sign that the body has been exposed to that particular food before. “IgG-based food sensitivity testing is not legitimate and often just tells you foods that you have eaten,” said Dr. Clay Jones, a pediatric and newborn hospitalist in Massachusetts. Research has shown that IgG responses to foods are normal and expected among healthy people with no food-related issues.
A high IgG response can also be a sign of food tolerance — the opposite of a food sensitivity. Multiple studies have found that after children recover from food allergies, their bodies often start making more IgG in response to that food as a sign that their bodies can handle it.
Moreover, these tests are not regulated by the FDA and haven’t been proven to diagnose anything. Researchers have never compared the results the tests provide after being administered to people with food-related conditions versus healthy people. And nobody has shown that they would provide the same results to the same person over time. “These are very basic steps that any reliable test must meet in order for it to be a validated test,” Dr. Stukus said, “and these food sensitivity tests fail on all three counts.”
Some of the companies who make these tests have been cited by the FDA for questionable practices on other fronts. For instance, KMBO Diagnostics, which sells a FIT test that claims to measure “sensitivities for up to 176 different foods, colorings and additives,” received a warning letter from the FDA in 2020 for selling an unauthorized Covid-19 antibody test.
Food sensitivity tests can increase the chance your kid will get sick
It’s bad enough that these tests don’t do what they say they’ll do, but they could actually increase the risk that a kid will develop food-related issues.
The science of food allergy prevention has shifted remarkably in recent decades. Doctors used to believe that parents should avoid feeding their babies allergens like peanuts or eggs, but now we know that introducing these foods early actually reduces the risk that infants will become allergic to them.
So when parents use food sensitivity tests and cut out foods based on their results, they are increasing the chance that their kids could become allergic to those foods down the line. “You can really cause significant harm,” Dr. Stukus said. Indeed, food allergies are much more common among kids who restricted their consumption of certain foods early in life, Dr. Lavine said. And as I’ve written in Slate, research suggests that if children have mild reactions to a food, continuing to eat that food may actually help them become more tolerant to it (though please only do this under the guidance of a board-certified allergist).
There are other potential downsides to unnecessarily cutting out foods, too. Doing so can greatly decrease quality of life and increase the risk that kids will develop nutritional deficiencies. One recent study found that kids who followed restrictive elimination diets were at an increased risk for developing eating disorders. These tests may also cause other underlying disorders to go undetected, Dr. Lavine said — a parent may remove a particular food from a child’s diet and think that solved their health issues, when in reality, the kid has another condition that is now left untreated. The parents may be “delaying the proper care that they need,” she said.
If reading this newsletter is making you break out in hives, I get it. I’ve shared a lot of worrying info! And if you’ve used these tests on yourself or your kids, there is no judgment here. Companies have done a brilliant job marketing them, and what parent doesn’t want a quick and easy diagnosis?
But if you suspect your kid may have a food allergy or intolerance, it’s far better to see an allergist or gastroenterologist and get a thorough evaluation, because most stomachaches and other digestive issues are attributable to other causes. “It's important that the health practitioner they're speaking to thinks about those odds and probabilities and practicalities and doesn't simply do a panel of food skin tests or order a panel of blood work,” Dr. Lavine said.
Indeed, even skin prick tests for food allergies (not sensitivities), which are legitimate and often administered by doctors, have to be interpreted very conservatively — more than half the time, the tests indicate potential allergies when the person doesn’t actually have one.
What will I do if my daughter’s tummy aches come back? I can’t say for sure, but hopefully I’ll take some deep breaths, re-read this newsletter, and perhaps make an appointment with a pediatric gastroenterologist.
Five Other Tests to Avoid
Here are five other food-related tests doctors warn parents to avoid — or, at the very least, to interpret with a huge grain of salt.
Muscle strength testing, also called applied kinesiology. These tests, popular among chiropractors, are based on the idea that muscle weakness is a sign of distant internal problems, including food sensitivities. During the test, a person is exposed to a suspected food, often by holding it, and then a muscle strength test is conducted by applying pressure to an extended arm. Unfortunately, the only study that has linked muscle strength tests with food sensitivities relied on IgG-based food sensitivity tests to establish subjects’ food sensitivities, which …. yeah. Is a huge problem.
LEAP or MRT testing. LEAP, which stands for Lifestyle, Eating, And Performance, is a popular protocol that combines the MRT test (short for Mediator Release Test) with recommendations for a particular diet. MRT tests measure how the size of your blood cells change after exposure to food extracts, and they have never been shown to diagnose food sensitivities or allergies.
ALCAT or cytotoxic testing. These tests claim to identify foods that cause harmful immune system reactions by studying how a person’s white blood cells change in response to food exposure. The approach has been considered unreliable for decades.
Electrodermal or Vega testing. These tests measure how well the skin conducts electricity when there is a sealed vial of food extract in contact with an aluminum plate near the patient. A decrease in conduction is considered indicative of a food allergy. No research suggests that this approach can diagnose food allergies or intolerances.
Iridiology. This technique involves examining the eye’s iris for changes in colors or other characteristics. No studies have found that it can diagnose food allergies or intolerances.