Following the low FODMAP diet can be a huge pain in the butt. So, you may be wondering if you can take a food sensitivity test to identify your IBS triggers, instead. In this article, we'll talk about what food sensitivity tests do, how they work, and if they can help you find your dietary triggers
What's the Difference Between an Allergy and an Intolerance?
First of all, while some people with IBS do have food allergies when we talk about food triggers and IBS, we're talking about food intolerances or “sensitivities.” So, what's the difference?
A food allergy is when your immune system reacts to the proteins in everyday food as if it were something that might harm you. According to current research, true IgE-mediated food allergies affect 3.5-4% of the population.
Allergy symptoms may include itching, hives, trouble breathing, tingling or swelling in the lips or mouth, abdominal pain, nausea, vomiting, or diarrhea.
A food intolerance (or “sensitivity”) happens when foods that should be broken down and absorbed by the body continue to travel through the digestive stem, unabsorbed. As they travel, they may pull water into the bowel and be fermented by gut bacteria, which may lead to painful cramping, bloating, constipation, or diarrhea.
Unlike allergies, reactions caused by an intolerance will resolve as soon as the trigger has exited the digestive system.
How Are Allergies Diagnosed?
If you or your healthcare team suspect a food allergy may be the culprit behind your symptoms, the first thing your doctor should do is review your medical history. If they find evidence that an allergy is likely, they may send you for a skin prick/scratch test or a serologic study to test for allergies. So, what do these tests do?
When your body encounters a protein it doesn't recognize, it may identify the protein as a threat (damn you pollen!). If your body meets the protein again, it will release a set of antibodies called Immunoglobulin E (IgE). These antibodies are like tattletales that attach to specialized cells in your body called “mast cells” and white blood cells in the bloodstream called “basophil.” Once activated, the mast cells and basophils will begin to release histamine and other inflammatory chemicals, creating an allergic reaction that starts where you were first exposed (like your mouth, your lungs, or your digestive tract).
In a skin prick/scratch test, a tiny puncture is made in the skin, and a concentrated dose of the allergen is applied directly to the wound. This introduces the allergen directly to your bloodstream. If you do have an allergy, your body will produce a “wheal” around the contact site as your body releases histamine to combat the proteins.
In a serologic study, a small sample of blood is taken to test for the presence of specific IgE antibodies.
While both of these tests can help determine if you have a true allergy, a medically supervised “oral food challenge” is the gold standard in testing for food allergies.
To complete an oral food challenge, you eat the test food in increasing amounts while in a medically supervised environment. The medically supervised environment is key here, friends! So, please don't try this one at home.
What Are Food Sensitivity Tests?
Commercial food sensitivity tests are modelled after an IgE serologic test. But, instead of looking for the antibody IgE, they look for an antibody called Immunoglobulin G (IgG).
The tests may be completed by sending a blood or hair sample to a lab or using at-home finger prick test to collect a blood sample.
Testing kits typically cost between $300 – $700 and usually test somewhere between 90-100 foods. The tests are available online and through many naturopathic clinics in North America.
The Problem with Sensitivity Tests
There are a few things we need to talk about here. First, research has shown that our bodies produce the antibody IgG every time we are exposed to specific proteins; whether we react to them or not. So, while an IgG test can show you what you've eaten recently, it can't necessarily determine if you're sensitive to that food.
Second, research is starting to show that IgG may actually indicate tolerance to foods, not intolerance. Several studies have shown that as individuals become more tolerant of foods they were allergic to, their levels of IgE decrease and their levels of IgG increase. This may explain why IgG levels are often higher in foods we eat regularly – like dairy, wheat, and eggs.
Third, IgG and other food sensitivity test currently aren't supported by any scientific body. In 2012, the scientific community's concern over the use of food sensitivity tests compelled Stuart Carr of the Canadian Society of Allergy and Clinical Immunology (CSACI) to release an official position statement on IgG testing.
In his statement, he stressed that no body of research currently supports IgG testing for the use of predicting food sensitivities. His position is supported by both the American Academy f Allergy Asthma and Immunology and the European Academy of Allergy and Clinical Immunology.
He also confirmed that current research suggests the presence of IgG to a specific food is a marker of exposure and tolerance to that food. So, positive test results for food-specific IgG would be expected in normal, healthy individuals.
Finally, and most importantly, since IgG levels are often the opposite of IgE levels, based on a food sensitivity report, a person with a true allergy may inadvertently add back food they're allergic to with life-threatening consequences.
Food Sensitivity Tests and IBS
Food sensitivity tests pose a unique problem for people with IBS. As many people have already cut out large groups of foods, fast before leaving the house, or eat as little as possible to avoid triggering their symptoms.
Because food sensitivity tests report higher levels of IgG in the foods we eat regularly, people with IBS will likely find many of their “safe foods” are listed as food sensitivities.
Aside from the emotional upheaval of feeling like no food is safe to eat, food sensitivity tests may lead people with IBS to further restrict their diets without any real benefit to their health. This can lead to nutrient deficiencies and malnutrition, as well as lowering the overall quality of life for people with IBS.
If you need help finding your IBS food triggers, the low FODMAP diet is a short-term program designed to help people with IBS test several common dietary triggers. Research has shown the program helps 3 out of 4 people with IBS reduce their symptoms by up to 75%, so it's worth investigating further.
While food sensitivity tests claim they can help you identify over 100 food sensitivities, research has shown that, currently, they can't deliver on that promise. If you need help finding your dietary triggers, save your money and try an elimination/re-challenge test (like the low FODMAP program) with your healthcare team.
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© 2019 Amy Agur – The FODMAP Formula
- Abrams, E. M., & Sicherer, S. H. (2016, October 18). Diagnosis and management of food allergy. Retrieved from http://www.cmaj.ca/content/early/2016/09/06/cmaj.160124.full.pdf html
- Abrams, E. M., & Sicherer, S. H. (2016, October 18). Diagnosis and management of food allergy. Retrieved from http://www.cmaj.ca/content/188/15/1087
- Carr, S., Chan, E., & Lavine, E., Et.al. (2012). CSACI Position statement on the testing of food-specific IgG. Allergy, Asthma, and Clinical Immunology : Official Journal of the Canadian Society of Allergy and Clinical Immunology, 8(1), 12. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3443017/.
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- Food Allergy Vs Food Intolerance in Patients With Irritable Bowel Syndrome. (n.d.). Retrieved from http://www.gastroenterologyandhepatology.net/archives/january-2019/food-allergy-vs-food-intolerance-in-patients-with-irritable-bowel-syndrome/
- Gocki, J., & Bartuzi, Z. (2016). Role of immunoglobulin G antibodies in diagnosis of food allergy. Postepy Dermatologii I Alergologii, 33(4), 253-6. doi:10.5114/ada.2016.61600
- Lavine, E. (2010). Blood testing for sensitivity, allergy or intolerance to food. Canadian Medical Association Journal, 184(6), 666-8. doi:10.1503/cmaj.110026
- Niec, A., Frankum, B., & Talley, N. (1998). Are adverse food reactions linked to irritable bowel syndrome? The American Journal of Gastroenterology, 93(11), 2184-2190. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/9820394/.
- Sampson, H. (2004). Update on Food Allergy. Journal of Allergy and Clinical Immunology, 113(5), 805-819. doi:10.1016/s0091-6749(04)01145-5
- Stapel, S. O., Asero, R., Ballmer-Weber, B. K., Knol, E. F., Strobel, S., Vieths, S., & Kleine-Tebbe, J. (2008). Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy, 63(7), 793-796. doi:10.1111/j.1398-9995.2008.01705.x
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