The tests often purport to check for sensitivities to hundreds of common foods, many of which rarely trigger food allergies, such as sugar or yeast. Blood is exposed to a panel of food proteins, and the labs measure the degree of IgG antibody that binds to each food.
But while IgE can indicate the presence of an allergen, IgG hasn't been shown to be a similar marker for intolerance. Instead, IgG is believed to indicate exposure to food and possibly even tolerance, Lavine wrote in the Canadian Medical Association Journal.
"There is no IgG testing of value," said Robert Wood, a professor of pediatrics and chief of pediatric allergy and immunology at Johns Hopkins University in Maryland. "All of us make IgG to the foods we eat, and they are not related to disease, including food intolerance."
Meanwhile, nearly everyone who takes these tests is told he or she has some kind of intolerance. One Florida lab boasts that "95 percent of the people we've tested show that one or more foods they regularly eat cause a toxic reaction in their body."
Proponents of the testing, primarily integrative physicians or alternative health practitioners, argue that the tests can be useful even if they are imperfect. IgG-based testing "showed promise, with clinically meaningful results," according to a 2010 review published in the journal Nutrition in Clinical Practice.
Some suggest that the test results could be used to guide which foods are chosen for testing through elimination from the diet, a trial-and-error process that can be time-consuming and difficult.
Peter Whorwell, a professor of medicine and gastroenterology at the University Hospital of South Manchester in Britain, found in 2004 that using IgG antibodies to guide food elimination diets may be effective in reducing the symptoms of irritable bowel syndrome.
The tests have particular appeal to people who have been coping with chronic symptoms but repeatedly hear: "We can't find anything wrong." When Jeffrey Sesol, of Homer Glen, started feeling strangely fatigued and achy, he went to his internist, a gastroenterologist, a neurologist and a rheumatologist, but no one had an answer.
"Grasping for straws," he went to see chiropractor Nicholas LeRoy at the Illinois Center for Progressive Health in Chicago.
LeRoy took Sesol off the acid reflux medicine he'd been taking for years — something no other doctor suggested — and ordered food allergy testing. Out of 150 foods tested, 33 registered positive, including yeast, wheat, eggs, milk, beans, cheese, garlic, ginger, nuts, lemon, mushrooms, rice, sesame, sugar and squash.
"The list was overwhelming, but I took out as many foods as I could," Sesol said. Within weeks his energy returned, he said, and after 45 days his acid reflux and aches disappeared.
"It was life-changing for me," said Sesol, 51, who now tries to avoid wheat, eggs, milk, brewer's yeast and baker's yeast but has added other foods back in his diet, including cheese. The test also helped his daughter, 24-year-old Amy, who was having similar symptoms, Sesol said.
LeRoy said testing has been extremely effective for his patients. "Ninety-five percent of the time I run a test, for whatever reason, it ameliorates a condition," he said. "There can be a relationship between foods and things that wouldn't seem likely related — asthma, chronic sinusitis and other systemic issues."
Some observers say personalized test results may not be as important as overhauling a lousy diet. Eliminating processed foods makes almost everyone feel better, said nutrition specialist Kelly Dorfman, author of "What's Eating Your Child? The Hidden Connections Between Food and Childhood Ailments."
Many insurance companies will not cover tests for intolerance. For example, although Blue Cross and Blue Shield of Illinois pays for allergy testing and therapy when medically necessary, it no longer covers IgG blood tests and at least 13 other testing methods that it considers experimental and unproven.
Sesol's insurance company paid for the acid reflux medication but didn't cover his $1,540 bill for food intolerance testing.
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