Brian Cassella, MCT
CHICAGO — According to one lab that tests for "toxic food syndrome," eating green peppers may cause bloating or lethargy. Lemons might trigger headaches. Other common foods like corn, soy, egg whites, whey and chicken "may act like a poison in your body," the website warns.
This company and others promise to detect such hidden problems with blood tests that can range in cost from hundreds to thousands of dollars, depending on how many foods are tested for.
Other health practitioners may say they can diagnose food sensitivities by assessing muscle strength, by analyzing hair, gastric juice or body tissue, or by reading the body's "energy pathways." Consumers are told that dietary triggers can cause gastrointestinal complaints such as heartburn or irritable bowel syndrome as well as fatigue, attention deficit problems, autoimmune diseases and arthritis.
But allergists and gastroenterologists say that although food intolerance does occur — most of it involving specific food sugars like lactose or fructose — the tests being marketed to consumers have no scientific basis. Blood tests for food sensitivities are prone to false positives that can lead people to eliminate harmless foods from their diets, they say.
The best way to test for the problem is to eliminate various foods from the diet until the symptoms clear, then reintroduce them one at a time, experts say. None of the other tests is recommended by U.S. or European allergy or immunology societies or the National Institutes of Health.
"Blood testing is confusing to patients," said Elana Lavine, a pediatric immunologist in Toronto who now spends part of her time counseling anxious parents whose children have undergone food sensitivity testing. Armed with their itemized results, which list dozens of forbidden foods, they ask her what to feed their children.
Part of the confusion lies in the difference between food intolerances and allergies, terms that are often used interchangeably by testing companies, health practitioners and even in peer-reviewed medical journals.
In an allergic reaction, the immune system overreacts to a food by producing an antibody called Immunoglobulin E that causes hives, vomiting, diarrhea and respiratory problems, among other symptoms. To diagnose an allergy, allergists use a blood test that checks for IgE, skin prick testing and other methods. The gold standard is an oral food challenge, which involves eating small doses of the suspect food under medical supervision.
Food intolerances are unpleasant reactions that do not involve the immune system, according to the National Institute of Allergy and Infectious Diseases. They can be caused by enzyme deficiencies, sensitivities to food additives such as sulfites and monosodium glutamate, or reactions to naturally occurring chemicals.
For example, people who lack an enzyme needed to digest sugar in milk have lactose intolerance. Sulfites used to preserve dried fruit, canned goods and wine trigger asthma attacks in sensitive people.
Adverse reactions to wheat or the protein gluten come in several forms. Celiac disease is an immune system reaction to gluten that causes inflammation in the small intestine. A wheat allergy is an allergic reaction to wheat, almost always caused by the gluten. And gluten sensitivity means a person has symptoms after ingesting gluten but doesn't have either of the other conditions, said Stefano Guandalini, founder and medical director of the University of Chicago's Celiac Disease Center.
Lavine and other critics say the food sensitivity tests being marketed are muddying the waters for people with legitimate allergies, which are on the rise. There's a big difference between a child who has a true milk allergy and another who has been labeled with a milk "sensitivity," said Lavine.
Blood tests are a common way to test for sensitivity or intolerance; many of these also involve an antibody, this one called Immunoglobulin G, or IgG.
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