Food sensitivity tests claim to examine our tolerance to a range of different foods, and assert that intolerances can lead to various illnesses. But how accurate are these tests, if at all?
Introduction
When I googled the term ‘food sensitivity test’, I was met with nine advertisements of local clinics offering this service. This is likely because around 25% of people believe they have food allergies, even though fewer than 2% of adults have received a formal diagnosis of a food allergy (1).
With the widespread prevalence of allergy-like symptoms, it’s no wonder that food sensitivity tests are so common. Therefore, in this article, we discuss whether food sensitivity tests are accurate or not—so you can be better informed if you were thinking about booking a test.
The 14 most common food allergens. Image source: Dot It.
What is Food Sensitivity?
If we eat a food and have an adverse (bad) reaction to it, that’s called food hypersensitivity (Figure 1). This food hypersensitivity can then be classified as either:
A food allergy, or
A food intolerance
Food Allergy
A food allergy is an adverse reaction to food that is driven by the immune system, and can be divided into either an IgE-driven food allergy, or a non-IgE-driven food allergy. An IgE-driven food allergy means that the adverse reaction to food is driven by an antibody called Immunoglobulin-E (IgE), which is formed by the immune system in response to an allergy. On the other hand, non-IgE-driven food allergies are reactions driven by other pathways.
Food Intolerance
A food intolerance is not driven by the immune system; rather, it is driven by other processes in the body such as reactions driven by enzymes (e.g., lactose intolerance), as well as those driven by substances like alcohol. One major difference between food allergies and food intolerances is that the latter is dose-dependent, while food allergies are not. In other words, even a trace amount of food would set off an allergic reaction, but if you were intolerant to a food, you can often eat some amount of it before any symptoms appear. The threshold of intake upon which symptoms occur may differ from food to food, and from person to person.
Figure 1. Food hypersensitivity reactions are either allergies (immune-mediated), or intolerances (mediated by enzymatic reactions, pharmacological reactions, or other reactions). Image source: Oncohema Key
Food Sensitivity Tests
Food sensitivity tests are blood tests that look for an antibody called Immunoglobulin-G (IgG). These antibodies are very common in the blood, and are elevated after exposure to a compound. In addition, IgG antibodies can stay in our blood for up to three months.
Are They Accurate?
The short answer is no. The longer answer is that there is no standardised methodology for IgG testing, and there is little evidence that food sensitivity tests can accurately measure IgG in humans (2). What’s more, even if the test was valid and reliable, IgG antibodies are not an indication of intolerance to a food. In fact, the reality is quite the opposite.
If you recall that IgG antibodies are elevated for up to three months after exposure to a compound, this means that if IgG levels are elevated after eating a food, this actually reflects tolerance to that food (3). In fact, IgG antibodies are typically low in IgE-driven food allergies (4). So, ironically, food sensitivity tests are not highlighting foods that you’re intolerant to, but rather foods that you are tolerant to!
Summary
If you experience unpleasant symptoms after eating certain foods, save your money and pass on the food sensitivity test. Instead, contact a registered dietitian who specialises in gastrointestinal health. And if you want to learn more, check out the Sigma Statement on this topic from the guys over at Sigma Nutrition. Indeed, this article was based on the evidence provided in their statement, so do check them out as they have some great nutrition science content.
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Thanks for reading, and have a great weekend!
Patrick Elliott, BSc, MPH
Health and Nutrition Science Communication Officer at Training121
Instagram: @just.health.info
Twitter/X: @PatrickElliott0
References
(1) Cianferoni A, Spergel JM. Food allergy: review, classification and diagnosis. Allergol Int. 2009;58(4):457–66. Available at: https://www.sciencedirect.com/science/article/pii/S1323893015307292
(2) Mullin GE, Swift KM, Lipski L, Turnbull LK, Rampertab SD. Testing for food reactions: the good, the bad, and the ugly. Nutr Clin Pract. 2010 Apr;25(2):192–8. Available at: https://aspenjournals.onlinelibrary.wiley.com/doi/full/10.1177/0884533610362696
(3) Gocki J, Bartuzi Z. Role of immunoglobulin G antibodies in diagnosis of food allergy. Postepy Dermatol Alergol. 2016 Aug;33(4):253–6. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5004213/
(4) Tang ML, Martino DJ. Oral immunotherapy and tolerance induction in childhood. Pediatr Allergy Immunol. 2013 Sep;24(6):512–20. Available at: https://onlinelibrary.wiley.com/doi/10.1111/pai.12100
Technical Terms
Food allergy: An adverse reaction to a food that is driven by the immune system. Food allergies can be divided into two groups: IgE-driven food allergies, which are driven by an antibody called Immunoglobulin-E, and non-IgE-driven food allergies, which are driven by other pathways.
Food hypersensitivity: A condition where the body reacts in an exaggerated way to certain foods. These reactions can be either food allergies or food intolerances.
Food intolerance: An adverse reaction to foods that is not driven by the immune system. Food intolerances are often driven by enzymatic reactions (e.g., lactose intolerance) or pharmacological reactions (e.g., flushed skin from alcohol).
Antibodies: These are special proteins created by the immune system to help defend the body against harmful substances, like bacteria or viruses. Immunoglobulin-E (IgE) is produced if an individual is allergic to compounds in certain foods, whereas immunoglobulin-G (IgG) is produced after exposure to certain compounds in foods, and reflects tolerance of such foods.
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