You may have seen commercials and advertisements for these ‘mail-in’ food sensitivity tests. Rams lineman, Andrew Whitworth, and Panthers running back, Christian McCaffery, follow a strict diet based on it. What does science say about blood testing for food sensitivity?
A food sensitivity is different from a food intolerance and/or a food allergy. An intolerance happens when the body does not produce a certain enzyme to properly digest certain foods. An allergy is an immune response to a harmful substance. Both of these conditions have medical definitions and can be clinically diagnosed. On the contrary, a sensitivity does not have a medical definition and can be assigned to a range of symptoms.
A blood test for an allergy measures for the protein immunoglobulin E, or IgE (science nerd alert!). If there is IgE, there is an immune response and an allergy can be diagnosed. A blood test for a food sensitivity measures for the protein immunoglobulin G, or IgG. IgG has not been shown to be an accurate indicator of food sensitivity or allergy. Conversely, IgD has been shown to be a response to a food tolerance (not intolerance). Also the Canadian Society of Allergy and Clinical Immunology, the European Academy of Allergy and Clinical Immunology, and the American Academy of Allergy, Asthma, and Immunology have presented research papers, statements, and endorsements that a positive IgG blood test result are expected in healthy individuals.
Whitworth, McCaffery, and others have adopted an unnecessarily restrictive elimination diet. Positive feedback and results from food sensitivity testing are likely due to the placebo effect and an adherence to a diet that consists mostly of nutrient dense and unprocessed foods. The best way to diagnose a true food allergy is through a skin prick test with your physician. If you feel you may have a food intolerance, we recommend you work with a dietitian to trial an individualized elimination diet plan. An elimination diet is the most effective way to identify food or multiple foods that may be causing certain symptoms.