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Food intolerance: A home test kit may point out what foods you need to avoid. But is it accurate?

Depending on the test type, you’ll pluck several hairs or prick your finger to drop blood onto a paper card, and then mail in your sample. Within days or weeks, you’ll receive digital results, including a list of foods that may be causing problems.

Food intolerance: A home test kit may point out what foods you need to avoid. But is it accurate?

(Photo: Steve Legato/The New York Times)

Food is one of life’s pleasures, but it can also be a source of pain – especially if you’re experiencing digestive issues like heartburn, abdominal pain, bloating or diarrhoea regularly. When those symptoms strike, you may wonder: Are certain foods to blame?

Food sensitivity tests promise to supply answers. For decades, these tests were offered mainly in providers’ offices in alternative medicine settings. Now, they are increasingly available as at-home tests you can purchase online or on drugstore shelves. Manufacturers claim that with several drops of blood or a few plucked hairs, they can identify the foods that are causing your discomfort. Once eliminated from your diet, you’ll be on the road to relief.

That a simple test could guide dietary changes and improve common, disruptive symptoms is certainly appealing. But do these tests work? We asked some experts and looked into the research to find out.

WHAT IS A FOOD SENSITIVITY, ANYWAY?

According to Dr David Stukus, director of the Food Allergy Treatment Center at Nationwide Children’s Hospital in Columbus, Ohio, the term food sensitivity is used more in marketing than in medicine. “There really is no consensus definition of what a food sensitivity is,” he said.

The companies selling these tests typically describe it as what happens when a specific food triggers digestive issues or gut inflammation, causing symptoms like abdominal pain, bloating or headaches. Symptoms may appear hours or even days after eating, and often resolve when the offending food is avoided.

(Photo: iStock/Doucefleur)

When physicians or dietitians refer to such issues, they’re more likely to use the term food intolerance, Dr Stukus said (though some may use food sensitivity, too), like with lactose intolerance, which can cause constipation, diarrhoea and bloating as a result of difficulty digesting the sugar found in milk. Similarly, people with irritable bowel syndrome may be sensitive to certain kinds of carbohydrates called FODMAPs, and altering their diet may relieve their symptoms.

A food intolerance or sensitivity is different from a food allergy, Dr Stukus said, which is an immune reaction to certain foods that can cause more severe symptoms like vomiting, hives, shortness of breath or even life-threatening anaphylaxis, usually within minutes of eating even a small amount. There are also more chronic immune reactions to foods, like those from celiac disease, a serious autoimmune condition triggered by gluten.

HOW DO FOOD SENSITIVITY TESTS WORK?

At-home food-sensitivity test kits can be ordered online or purchased over-the-counter at drugstores. Depending on the test type, you’ll pluck several hairs or prick your finger to drop blood onto a paper card, and then mail in your sample. Within days or weeks, you’ll receive digital results, including a list of foods that may be causing problems.

Some tests claim to determine your sensitivity to hundreds of foods and ingredients by measuring the “bioresonance” of your hair, an unproven technique used in holistic or complementary medicine that involves measuring the energy wavelengths coming from your body. Others measure the levels of certain antibodies, called IgG antibodies, in your blood.

Still other tests, called Alcat and MRT tests, require a blood draw from a lab and measure how the size of your blood cells change after exposure to food extracts in a test tube, said Dr John M. Kelso, an allergist at Scripps Clinic Carmel Valley in San Diego.

ARE FOOD SENSITIVITY TESTS ACCURATE?

Aside from the breath tests that gastroenterologists sometimes use to diagnose certain intolerances, like those to lactose or fructose, there aren’t validated tests for food intolerances or sensitivities, said Tamara Duker Freuman, a registered dietitian at New York Gastroenterology Associates in New York City. The only way to figure out if you are sensitive to certain foods or ingredients is to see how your symptoms change after eliminating them from your diet, ideally with the help of a registered dietitian or physician, she said.

(Photo: iStock/Amorn Suriyan)

This can be a slow process involving trial and error, and the companies selling food-sensitivity tests market them as a shortcut. But medical organisations, including those in the United States, Europe and Canada, have recommended against using food sensitivity or intolerance tests because there is no good evidence that they work.

“There isn’t anything in your hair that would tell you anything about your sensitivity to food,” Dr Kelso said. And the antibodies measured in the IgG tests are produced as part of the immune system’s normal response to foods; they haven’t been shown to correlate with symptoms or intolerances, Dr Stukus said. “It’s really just a reflection of what you’ve eaten.”

Similarly, the way blood cells in a test tube interact with food extracts, as in the Alcat and MRT tests, is likely different from how they encounter them in the body, Dr Kelso said. None of these tests have been subjected to the kind of high quality clinical trials necessary to validate their usefulness for patients, he added. (Oxford Biomedical Technologies, the company that sells a blood cell MRT test, did not respond to a request for comment.)

Christina Song, a spokeswoman for Everlywell, a company that sells at-home IgG food sensitivity tests, pointed to several studies – mostly in people with IBS and some funded by the companies that sell the tests. In them, researchers found that eliminating high IgG foods reduced symptoms like abdominal pain and bloating.

(Photo: iStock/Tharakorn)

But in general, many of the studies that have reported positive results for food sensitivity tests have been small and often lacked proper control groups, said Dr Lin Chang, a gastroenterologist and professor of medicine at the David Geffen School of Medicine at the University of California, Los Angeles.

In a small trial of 58 IBS patients, published in 2017 and funded by Cell Science Systems, the company that sells the Alcat food sensitivity test, researchers found that those who avoided foods flagged as intolerant by the test for four weeks reported greater improvement in their symptoms than control participants.

One of the study’s authors, Dr Wajahat Mehal, a professor of digestive diseases at the Yale School of Medicine, said he found the results convincing enough that he now offers the test to his patients with IBS. Yet he acknowledged that most of his colleagues would want to see much larger and longer clinical trials before recommending it.

According to the American College of Gastroenterology’s 2021 clinical guidelines for the management of IBS, the study’s results “are intriguing but need to be confirmed.”

“Multiple tests are marketed to diagnose food intolerances; however, none have been validated, and most have not been subjected to rigorous, blinded trials,” the guidelines say.

Elaine Byers, chief technical director of 5Strands Affordable Testing, a company that sells hair-based food intolerance tests, said that “this is an entry level test which will allow consumers to take a proactive approach to personal wellness. It was not designed as a diagnostic tool.”

ARE THERE ANY DOWNSIDES TO TRYING THESE TESTS?

There can be. Food sensitivity testing can cause people to unnecessarily avoid a long list of foods, missing out on those they enjoy and potentially becoming susceptible to nutrient deficiencies, said Dr Frances Onyimba, a gastroenterologist and assistant professor of medicine at the University of Maryland School of Medicine.

The cost of food sensitivity testing is generally not covered by insurance and can range from less than US$100 for hair-based tests to US$600 or more for blood cell size tests. The Everlywell Food Sensitivity Comprehensive Test retails online for US$299.

(Photo: iStock/Gilnature)

The tests can also leave people anxious about eating, which can sometimes develop into eating disorders, Dr Stukus said. “People come to me saying that they can’t eat 15 to 20 different foods because of some unvalidated test, and it is very challenging to get them to understand why that’s not the case,” he said.

Everlywell acknowledges on the bottom of its online order page that eliminating and restricting foods “can lead to or trigger disordered eating behavior.” It does not recommend those who have or are recovering from eating disorders to take the test.

None of the tests currently on the market have been evaluated by the Food and Drug Administration, James McKinney, a press officer for the agency, said in an email.

IF NOT A FOOD SENSITIVITY TEST, THEN WHAT?

If digestive symptoms are interfering with daily life, it’s worth seeing a health care provider to figure out the cause, which may or may not be food-related, Dr Chang said. “Abdominal pain can mean pancreatic cancer, it can mean IBS, it can mean I ate spicy food.”

Some of Freuman’s patients, she said, think they have a food sensitivity and are surprised when she tells them the real cause of their symptoms is likely constipation.

Dr Stukus emphasised that it takes more than just a simple test to come up with a diagnosis. “We don’t just do a bunch of tests and then see what the tests show,” he said.

If she’s ruled out other explanations and a food intolerance seems plausible, Dr Onyimba said she’ll recommend that patients work with a registered dietitian to make dietary modifications. This “can be a longer process, but it’s a process that’s worthwhile,” she added, and it’s better than “avoiding a food for the rest of your life, based on a hunch or a test that’s not validated.”

By Alice Callahan © 2022 The New York Times

This article originally appeared in The New York Times.

Source: New York Times/ss

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