Misunderstood? Setting the Record Straight on Food Sensitivity Testing

Discover if “food sensitivity testing” is right for you.
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setting the record straight on food sensitivity testing

Do a Google search for “food sensitivity testing” and you’ll be left even more confused about how or whether to test your food sensitivities than you have been by the types of foods you should eat for your condition! 

Alongside the testing kits you may have in mind, you may see something like this:

Understandably, this doesn't instill confidence for companies selling home food sensitivity testing kits. As a nutritional scientist specializing in gut health, I feel that these types of articles only tell half the story. Having had my own emotional health journey, I empathize with those seeking to take control of their own health. At home lab tests can be useful in getting to the bottom of chronic conditions that are undiagnosable by doctors like fatigue, stress and insomnia as told by one of our very own writers Sarah Ban, "I Took An At Home Lab Test for My Chronic Fatigue, Stress and Insomnia." I hope that I can help readers understand all the facts in order to determine the value of these tests and make the right decisions with regards to not only the types of tests you should consider, but the health practitioners you should seek guidance from.

So What Is Food Sensitivity?

You may know the feeling well. When your belly swells up and you get gas just moments after you eat foods like beans, broccoli, onions, bread, milk, or even eggs, you know that your body just isn’t tolerating the particular type of food very well. You put two and two together and know that you should avoid these foods to control your tummy troubles.

What about headaches, joint pain, low energy, anxiety or skin issues? These too can be associated with the food you put on your plate. As you continue to eat the offending food, your symptoms get worse, and it can continue for years without you ever knowing that it’s specific types of food that you’re actually sensitive to.

Both digestive and body-wide manifestations, and the increasing number of inflammatory diseases that plague our society is one of the reasons there’s an ever-growing interest in the world of food reactivity. It has left many of us questioning why our body responds to the things we put in our mouth and, more importantly, what we can do to stop it from leaving us inflamed and in ill health.

How Your Body Reacts to Food 

Let’s start with why your body may develop a sensitivity to certain types of food. As the topic is a bit clinical I've done my best to communicate it in plain language. 

Your body's defenses lie with the immune system. Any foreign invader that enters the body is immediately sized up by the immune system and promptly taken care of if it poses even the slightest threat to your health. The immune system uses molecules called immunoglobulins (Ig) to determine the risk of these foreign invaders, where they also play a role in the invader’s destruction. The five main Ig are IgA, IgD, IgE, IgG and IgM.

When it comes to food, it’s IgE and IgG that are most important. IgE are those that play a role in true food allergies where an IgE-mediated response results in a sudden onset of life-threatening symptoms(1) upon exposure to foods like peanuts and shellfish, for example.

Food sensitivities, which have been said to be caused by an IgG-mediated response, may bring about symptoms 30 minutes to 48 hours after the exposure and can include gut-related symptoms of those that affect the entire body(2). IgG is what many food sensitivity tests measure, as a means to determine the response that the immune system has when these foods are ingested(3).

There is, however, a main concern.

The Case Against Food Sensitivity Tests

A review study, published by the Dermatology and Allergology journal in 2016, suggests that many scientific societies stress that the results of specific IgG testing for food sensitivities has no significance in the diagnosis of the sensitivity(4).

Why?

Because the body’s natural response to the ingestion of food launches IgG responses(5)

Let’s break that down… Most food is digested by a variety of processes that are functions of the digestive system. From chewing to peristalsis - which is the movement down the food pipe - to stomach acid, and digestive enzymes, each step of the way, food is broken down into smaller particles that the body recognizes as useful. Carbohydrates become simple sugar, proteins become amino acids, and fats break down into fatty acids. That’s the case for most of the food you eat.

In a healthy individual, there is evidence to suggest that as much as 15% of proteins aren’t actually broken down(6), and this is where the immune system comes in to ensure they are dealt with in the appropriate way. You can just imagine from the different types of food you eat on a regular basis how much of the other compounds need the immune system to help out, which is where IgG and its role in food become significant(7,8).

Where food sensitivity testing is concerned, higher IgG levels suggests a higher response of the immune system to a particular food, and these levels are then used to base recommendations for dietary restrictions for those foods.  

Using IgG Testing Correctly

When we consider that a normal body response is to increase IgG, food sensitivity testing may seem like hype. Particularly when the foods you eat regularly are those that show up the most. 

Which means, there may well be value in using at-home food sensitivity testing, should this be something you’re interested in pursuing.

It appears that it’s the interpretation that needs to be considered and taken at face value. Where IgG responses are high for certain foods, the process of their breakdown needs to be considered as well as the general health of your digestive tract. 

For example, where certain types of fibrous food show high ‘reaction’ levels, one can consider that the digestive enzymes the body produces are insufficient to allow for proper breakdown of these foods. It is then necessary to support the body’s ability to produce these enzymes while limiting the intake of these offending foods until such a time that gut health has been brought back into balance, and the underlying cause of the IgG response has been targeted. 

Another common reaction is the change in the integrity of the gut epithelial barrier - a layer in your stomach lining. Normally impermeable to anything other than nutrients that it allows into your bloodstream, where leaky gut, for example, has developed, larger food particles and other allergens may now be allowed to pass through, which increases inflammation and immune response(9).

For this purpose, the results of a food sensitivity test can provide some valuable information as to what may be going on in your digestive tract, instead of a simple plan that has you eliminating foods from your diet that may, in fact, be good for you. Alongside these test results, it is recommended to work with a healthcare practitioner that may be able to help you to manage your health, in particular, when you are diagnosed with a medical condition, like IBS, for example. 

If I lost you, this is what you need to know. We’ve now found out that food sensitivity tests shouldn’t be used in isolation, and should be used as a suggestive tool, rather than a diagnostic tool. With guidance from the right healthcare practitioner, like a functional medicine doctor, IgG tests can be a useful tool in providing clues with regard as to what may be happening within your digestive tract and evaluating where IgG responses are unusually high for certain foods(10,11,12,13). Together, you can then determine an appropriate personalized plan of action to heal your gut. 

The following are the types of tests that are available.

Types of  Food Sensitivity Tests

Tip! If you contribute to an HSA/FSA, check with your benefits coordinator, as it is possible to get reimbursed for the cost of these food sensitivity tests.

IgG - as discussed above, these tests offer information of your exposure to food, and when used in conjunction with the advice of a healthcare practitioner, may help you to decipher the root cause of why you may feel you’re reacting to these foods. The cost for these tests, when ordered online, can be as low as $150.00 or as high as $700.00, depending on where you source them from. An inexpensive option, that measures IgG responses in 96 different foods is the EverlyWell test, which can help you determine your next course of action. 

ALCAT - the test requires a blood sample to be drawn and the change in size of the white blood cells is recorded as a measure to identify food sensitivities. It has been a popular test for those with IBS wanting to determine their trigger foods. While this test is still used by some, it is a predecessor of the next test, the MRT.

MRT - this test requires a blood sample to be drawn after which your white blood cells are exposed to particular foods. The change in your white blood cells may indicate a food sensitivity, however, there are few evidence-based, clinical studies to support the effectiveness of this type of test.

Gut microbiome testing - testing that which passes out of your digestive system is another suggested means to determine what your food sensitivities are. By taking a look into the types of gut bacteria you have, you may have a better understanding of why there is inflammation and where it is coming from. Viome, for example, is an at-home test ($399) that has you collect a stool sample, which is analyzed in terms of your microbiome and how it is functioning. This reveals personalized information as to whether you’re able to digest certain foods, whether the nutrients you’re eating are benefiting you, and more.

Finally, it’s important to remember that:

  • The jury is still out on whether these tests have any real merit as diagnostic tools for real food intolerances(14)
  • The foods that the lab use in their reactivity testing also plays a role in the response (e.g. raw versus cooked food, or even meal combinations)
  • A true food allergy needs to be tested using IgE responses and should be managed by an appropriate healthcare professional(15)
  • Removing whole food groups from the diet may reduce nutrient intake and lead to deficiencies

Finding the Right Health Practitioners

One of the final considerations to make when you go about testing for food sensitivities is the help you need to make sense of it all. Sometimes, it can be difficult to get proper advice without feeling dismissed by your family doctor. With clear flaws, biases such as personal knowledge of the practitioner and even the gender of the patient yielding different prescriptions, personalization of your treatment can be accompanied by numerous obstacles.

But, rest assured, there are many professionals out there who can help. An immunologist or allergist typically deals in immune-mediated food allergies (IgE), while an Integrative or Functional Medicine Doctor or a Naturopathic Doctor may be a better option when it comes to food sensitivities and intolerances (IgG). They are highly knowledgeable when it comes to functional tests like these, and they can offer you the advice you need to figure out the meaning of your results. They can then help you to integrate the results into your greater treatment plan, or propose any additional tests you require to determine the root cause of your sensitivities or food intolerances.

Be sure to think about all of these points as well as the cost of these tests before you place your hopes in what they mean as a way to ‘cure’ what ails you. Remember, instead of looking at one or two imbalances in isolation, you always need to consider the greater picture of your health to discover what’s really going on. 

If you have any thoughts or insights from your own experiences utilizing food sensitivity tests and working with health practitioners, please share in the comments below.

Editor's Note: The links to Everlywell and Viome in this article are affiliate links. By making a purchase through these links, we earn a commission. This helps our efforts in covering complex health topics by commissioning qualified health writers with backgrounds in healthcare, nutrition, and research.

Scientific References:

*Below are scientific papers that were reviewed and referenced in this article.  

  1. Schryver, E., et al. Local Immunoglobulin E in the Nasal Mucosa: Clinical Implications. Allergy Asthma Immunol Res. 2015 Jul;7(4):321-331. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4446630/
  2. Mygind N, et a;. Alergologia. In: Kruszewski J, Silny W, editors. Wrocław: Urban & Partner; 1998. pp. 136–7.
  3. Donaldson, G., et al. Gut microbiota utilize immunoglobulin A for mucosal colonization. Science. 2018. 360(6390):795-800. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5973787/
  4. Gocki J., et al. Role of immunoglobulin G antibodies in diagnosis of food allergy. Postepy Dermatol Alergol. 2016;33(4):253–256. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5004213/
  5. Wachholz P, & Durham, S. Mechanisms of immunotherapy: IgG revisited. Curr Opin Allergy Clin Immunol. 2004 Aug; 4(4):313-8. https://www.ncbi.nlm.nih.gov/pubmed/15238798
  6. Majka J, et al. Budowa i czynność jelita cienkiego. In: Dąbrowski A, editor. Wielka interna. Gastroenterologia. Warsaw: Medical Tribune Polska; 2011. pp. 165–84
  7. Agarwal S, et al. Mucosal immunity. In: Metcalfe DD, Sampson HA, Simon RA, editors. Food Allergy: Adverse Reactions to Foods and Food Additives. 4th edition. Oxford: Blackwell Publishing; 2008. pp. 19–29. https://adc.bmj.com/content/77/4/370.6
  8. Tang M, & Martino, D. Oral immunotherapy and tolerance induction in childhood. Pediatr Allergy Immunol. 2013 Sep; 24(6):512-20. https://www.ncbi.nlm.nih.gov/pubmed/23905867
  9. Zuo X, et al. Alterations of food antigen-specific serum immunoglobulins G and E antibodies in patients with irritable bowel syndrome and functional dyspepsia. Clin Exp Allergy. 2007 Jun; 37(6):823-30. https://www.ncbi.nlm.nih.gov/pubmed/17517095
  10. Stapel S, et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy. 2008 Jul; 63(7):793-6. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1398-9995.2008.01705.x
  11. Tay, S., et al. Patterns of immunoglobulin G responses to egg and peanut allergens are distinct: ovalbumin-specific immunoglobulin responses are ubiquitous, but peanut-specific immunoglobulin responses are up-regulated in peanut allergy. Clin Exp Allergy. 2007 Oct; 37(10):1512-8. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2222.2007.02802.x
  12. Hochwallner H, et al. Patients suffering from non-IgE-mediated cow's milk protein intolerance cannot be diagnosed based on IgG subclass or IgA responses to milk allergens. Allergy. 2011 Sep; 66(9):1201-7. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1398-9995.2011.02635.x
  13. Antico A., et al. Food-specific IgG4 lack diagnostic value in adult patients with chronic urticaria and other suspected allergy skin symptoms. Int Arch Allergy Immunol. 2011; 155(1):52-6. https://www.karger.com/Article/Abstract/318736
  14. Burks A, et al. ICON: food allergy. J Allergy Clin Immunol. 2012 Apr; 129(4):906-20. https://www.jacionline.org/article/S0091-6749(12)00254-0/pdf
  15. Sampson H, et al. Food allergy: a practice parameter update-2014. J Allergy Clin Immunol. 2014 Nov; 134(5):1016-25.e43. https://www.jacionline.org/article/S0091-6749(14)00672-1/pdf

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