The RWS Guide to Food Sensitivity Testing
Food sensitivity testing is one of the most hotly debated and misunderstood types of testing. Without understanding the core concepts and mechanisms driving the different types of food sensitivity, we’re reliant on the marketing claims of different labs, putting us in a vulnerable place as practitioners.
Let us help you clear up the confusion so that you can make an informed decision about which testing option is the best for you and your practice.
A hypersensitivity occurs when our immune system reacts aggressively and defensively towards something that is ultimately harmless: for example, a peanut or pollen. There are three types of hypersensitivity reactions pertaining to food.
Type I Hypersensitivity: Food allergy
This type of hypersensitivity is a true food allergy, and is always mediated by IgE antibodies
In a Type I Hypersensitivity the immune system determines that a substance (be that a particular food or an inhalant such as pollen) is not safe, and thus mounts a defense response. As part of this defense, B-cells produce IgE antibodies, which attach to mast cells packed with chemicals that can induce the hypersensitivity response. When the individual is exposed to that food or inhalant, the antigens attach to IgE receptors on the mast cells, which release mediators – the histamines and other chemicals that produce inflammation in the body.
Important considerations:
• It is not the IgE antibodies that create the symptoms, but the mediators (histamines, cytokines, and so on) released by the mast cells that cause the symptoms.
• In IgE allergic reactions, typically the more IgE a person has in their blood stream to a particular food, the more reactive and symptomatic they are. Research shows that there is a correlation between the amount of IgE produced and the severity of symptoms.
• Mast cells are found in the mucosa and tissue, but not in the blood. Thus the mediator release does not happen in blood, but in mucosa and tissue.
Testing for Type I Hypersensitivities is done via the blood and is testing for IgE antibodies in response to stimulus by food antigens. Information gleaned from these tests is clinically relevant to true food allergies alone. It tells you nothing about food sensitivities.
Of note: Over 80% of Type I Hypersensitivities are from 10 common foods, so testing for an extensive list of IgE food allergies isn’t usually necessary.
Type III Hypersensitivity: Immune Complex-mediated Hypersensitivity (Antibody food sensitivity)
A Type III Hypersensitivity involves the antibodies IgG and to a lesser degree IgM - whose response and action is different from IgE. These responses are considered food sensitivities, not food allergies.
In a Type III reaction, immune complexes made up of antibodies and antigens are created as a normal and necessary physiological process that help the body “clear the garbage” from the circulation and tissue. For example, when one has compromised gut permeability and absorbs large molecules of food into the bloodstream not usable as nutrients, these have to be cleared. Immune complexes do this job.
For the most part, immune complexes are readily removed from the system without doing damage, unless one of two things happens:
1. The immune complex is of a smaller size and reacts with complement, which causes mediator release and thus symptoms of inflammation.
2. The immune complex gets trapped in tissue somewhere, binds complement and activates the release of mediators, which cause inflammation and thus symptoms.
Important considerations:
• Much like with IgE food allergy responses, it is not the IgG or IgM antibodies that create the symptoms, but the mediators (histamines, cytokines, and prostaglandins) released in the process that cause the symptoms.
• Unlike IgE food allergy responses, there is no direct correlation with the amount of IgG or IgM in the blood and symptom manifestation. (Over 200 studies have been done investigating this correlation, and the overwhelming consensus is that there is a poor correlation.) This is because IgG and IgM immune complexes are a normal and natural part of the body “clearing the garbage” from the blood. It is only when the above two
conditions are met (the immune complexes are a smaller size or trapped in tissue) that mediators are released and thus inflammation and symptoms felt.
• For this reason, serum testing for IgG or IgM antibodies does NOT tell us about the most important aspect of food sensitivities: which foods are causing mediator release and thus inflammation and symptoms in the client.
Testing for Type III Hypersensitivities is done via blood testing, but if it is quantifying IgG or IgM antibody response to food antigens alone, it is not giving you clinically relevant information because it is not telling you which food antigens are causing actual symptoms. If this testing also includes some mechanism to quantify the mediator release and thus levels of inflammation, it is a more thorough and clinically relevant test.
Of note: Antibody production of any kind relies on exposure. For example, in the case of IgG, antibodies linger for about three weeks. Thus if an individual has not consumed the food in the three weeks prior to antibody testing, there can be a false negative.
Type IV Hypersensitivities (Cell-mediated, delayed hypersensitivity)
A Type IV Hypersensitivity is an often-overlooked but critically important type of food sensitivity that does not involve antibodies or the development of immune complexes. In this kind of hypersensitivity, antigens are taken up by antigen presenting cells directly and presented to T-cell, which, if they decide the antigen is a threat, create granulocytes to attack the antigen and release mediators.
There is substantial evidence that both IBS and migraines are due to Type IV hypersensitivity reactions.
Important considerations:
• Unlike Type I and Type III hypersensitivities, no antibodies are involved in this process.
• As with all types of hypersensitivities, it is not the mechanism that drives the symptoms – it is the release of mediators such as histamines, cytokines and prostaglandins that cause inflammation and symptoms
• Most common food sensitivity testing – particularly those focused on a specific type of antibody – miss this category of sensitivity altogether.
Testing for Type IV hypersensitivities is done via the blood and is testing for the release of mediators themselves and thus the degree of inflammation caused by a particular food or chemical. This type of testing is called mediator release testing. This testing will, by default, also capture mediator release from those IgG and IgM antibodies that are causing symptoms. As such, it is the most comprehensive test for food sensitivities overall.
Of note: Mediator Release Testing does not provide clinically relevant information regarding IgE food allergies, as the release of mediators from mast cells in an IgE reaction does not occur in the blood, but in tissue or mucosa.
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