It is possible to react to the consumption of certain foods through various symptoms such as digestive issues, migraines, rashes, or others. Symptoms can occur at any period during the course of a lifetime. How do you know if it is an allergy, intolerance, or food sensitivity, and how can you identify which foods are the culprits? Let’s demystify it together!
A food allergy is an abnormal response of the immune system following the consumption of a protein contained in a food. It usually occurs within a few minutes or the hour following the ingestion of a food. It can be accompanied by various symptoms affecting different parts of the body (digestive system, skin, nervous system, respiratory system, etc.) that can vary from person to person. It can be diagnosed by an allergist through a serum IgE dosage, i.e. a blood test that can look for the presence of a certain type of immunoglobulin, the IgE, characteristic of the allergic reaction. It is also possible to perform a skin tests that involves putting skin cells in contact with the suspected allergens, specifically by pricking the skin with a drop of the allergen or by placing a sticker containing the allergen onto the skin. The most common food allergens are: peanuts, other nuts (walnuts, almonds, hazelnuts, cashews), milk, eggs, fish, seafood, soy, sesame seeds, wheat, mustard and sulfites.
A food intolerance does not involve the immune system. It is often caused by the malabsorption of certain nutrients. Some intolerances, such as lactose, fructose, and sucrose intolerances, can be diagnosed with the help of a breath test. However, most food intolerances cannot be diagnosed through medical tests. An elimination diet based on a very specific protocol remains the best way to determine the presence of a food intolerance. For example, the Low FODMAP* Diet is a science-based approach to identify food intolerances in people with Irritable Bowel Syndrome (IBS).
Many tests are sold by companies to detect allergies, intolerances, or food sensitivities, which are based on science, and which have not been proven reliable or repeatable. The most popular involves the measurement of IgG antibodies, which are proteins produced by the immune system in response to exposure to external triggers such as pollen, food, or insect venom. Their presence simply reflects exposure to these triggers. IgG antibodies that are produced in response to food consumption are generally detectable in healthy people, whether or not diet-related symptoms are present. For example, people who perform these tests, which are often very expensive, receive a list of foods to avoid, usually very long, which are actually the foods that they have recently eaten. This leads to unnecessary dietary restrictions that can be harmful to long-term health. There is no credible evidence that measuring IgG antibodies is useful in diagnosing food allergies or intolerances, nor that IgG antibodies cause symptoms. The only exception is the use of IgG anti-gliadin antibodies to evaluate the effectiveness of a gluten-free diet in people with celiac disease. The Australasian Society of Clinical Immunology and Allergy (ASCIA) has issued a warning against the use of these tests. So, in short, the term food sensitivity is used by companies to sell IgG antibodies measurement tests, but is not a term validated by science.
*FODMAPs are fermentable carbohydrates that are partly responsible for causing symptoms in people with irritable bowel syndrome (IBS). For more info, read this article.