I was first diagnosed with irritable bowel syndrome (IBS) as a college freshman. Having barely had a yearly cold while I was a kid, feeling suddenly vulnerable to the whims of my body was a rude adjustment. I spent months going to the doctor, with nothing really helping. Had at-home food sensitivity tests existed when I was 20, I would have taken ALL of them. And I know I’m not the only one who’s gone through this.
Functional gastrointestinal disorders like irritable bowel syndrome, functional dyspepsia, and functional constipation impact up to 40% of the population within their lifetimes. A LOT of people live with these, and while many cases can be managed with lifestyle changes, these changes can be hard to maintain and don’t always give results. Today I’m explaining how those at-home food sensitivity tests work, and why these types of GI disorders are so difficult to fix.
Immunoglobulins and Food Sensitivity
The following is a very over-simplified explanation of how the immune system works. I’m just grazing the surface here, but it is super important to understand at least a little of this in order to understand how food sensitivity tests work. Here we’re focusing on immunoglobulins, also known as antibodies.
Immunoglobulins are proteins produced by white blood cells. They recognize antigens (bacteria, viruses, or allergens) and create specific defenses against these antigens.
There are five types of immunoglobulins, but in the context of allergy and food sensitivity, we’re only really going to talk about two: IgG and IgE. One other type, IgA, is occasionally addressed in the allergy/food sensitivity context because IgA deficiency is sometimes accompanied by gastrointestinal side effects, and IgA antibodies are tested to diagnose celiac disease.
IgE is the culprit behind hypersensitivity reactions — primarily allergy and asthma. IgE is present on mast cells, cells that are responsible for the allergic response through degranulation- a process that releases inflammatory mediators like histamine, heparin, and cytokines.
When a foreign antigen is recognized by IgE in tissues like the gut or respiratory tract, the mast cells begin to activate. As mast cells degranulate, this can cause vomiting, diarrhea, muscle contractions, increased mucous production, and coughing.
IgG is the most present antibody in the body. When our bodies are exposed to a foreign antigen, we create an initial number of antibodies against it, which eventually decreases and stabilizes over time. As we are introduced to the antigen again, our bodies retain knowledge of what they’ve been introduced to, and retain a “library” of these antigens so they would be ready to mount an immune response if necessary.
If this wasn’t enough for you and you’re interested in learning more about immunoglobulins, this is a bit more in-depth. If you’re looking for really next-level info, I found this immunology course on Coursera that has amazing reviews, and I may be starting it soon as well.
Allergy Tests vs. Food Sensitivity Tests
All this is to say that IgG testing for food sensitivities doesn’t tell us much. Since IgG is trained to identify and work against foreign proteins in the body, an IgG test can have a positive result for any foreign protein the body has previously come into contact with. This means that if you’ve eaten any certain food, you would likely have positive IgG test results for that food. It doesn’t mean that you’re having any kind of allergic reaction or sensitivity. It means that your immune system is doing its job, and recognizing foreign proteins.
An IgG immune response in this instance doesn’t necessarily mean your body is “fighting off” the food. For example, a study of children allergic to peanuts found that through oral immunotherapy — dosing peanut protein in small amounts to desensitize the body’s allergic reaction — IgE levels were lowered. However, at the same time, the childrens’ IgG levels increased, meaning an IgG response could be a marker of having been exposed to a certain food, not a marker of reactivity.
This difference is complex, so it’s absolutely understandable that most of us don’t know where to start. The confusion between food intolerance testing and allergy testing happens frequently enough that my allergist has a pre-printed packet about the difference between IgE and IgG testing to give patients when they get tested for allergies.
How At-Home Food Sensitivity Tests Work
All this said, food sensitivities definitely do exist — 65% of the world’s population likely has some level of lactose intolerance, and around 5% of the world has non-celiac gluten sensitivity. It’s no wonder people are looking for a way to figure out what might be causing them problems.
At home food sensitivity tests have recently come on to the market, with one test, the EverlyWell food sensitivity test, gaining a lot of traction when it aired on Shark Tank and secured $1 million from Lori Greiner.
But do these at-home food sensitivity tests work? Not really. They’re no different than the IgG-mediated tests offered in labs and doctor’s offices, meaning that they don’t measure sensitivity, but rather exposure to a given food. The fact that you can do them at home is a good selling point for convenience, but unfortunately, the testing is just not quite there.
Other Types of Food Sensitivity Tests
Basic IgG testing isn’t the only kind of food sensitivity test out there. There are tons of other, food sensitivity tests on the market, with varying degrees of scientific evidence to back them up.
I didn’t come across this test in my initial research, but after someone mentioned it to me, I decided to look into it a bit more.
- Hard to find which biological markers are being analyzed in this test on their website, although it looks to be IgG and IgA. They have a variety of assays for different sensitivities/concerns. I looked at Assay 10.
- Couldn’t find any peer-reviewed (e.g. PubMed or Google Scholar) articles about the validity of this test.
- There is one article from the Chief Scientific Officer at Cyrex that seemed to describe their main food sensitivity panel. In this article, he makes the case that most food sensitivity tests are lacking, as cooked food elicits a higher IgG, IgA, and IgM response.
While his article was convincing in that we should be testing immune response against cooked foods, there’s still one problem. Does this food sensitivity test actually align with symptoms of food sensitivity?
- One study evaluated 84 subjects with IBS to see if the foods that they self-reported as symptom-producing were also the same foods that would show up through food sensitivity tests.
- For these subjects, a panel of total IgA, IgA and IgG against gliadin and gluten, IgA against lactalbumin, lactoglobulin, casein, and ovalbumin, as well as tests for celiac disease were taken. These would, in theory, measure intolerance to dairy, eggs, and gluten.
- Although many people reported intolerance to these foods, there was no statistically significant correlation between self-reported food intolerances and the results of the panels that were taken, meaning that there isn’t enough overlap between what these panels detect and what people report as intolerances for this type of testing to be sufficient in evidence-based practice.
These studies are important, as they don’t deny that food intolerances may provoke symptoms in IBS, but rather, that many of these diagnostic methods available fail to predict or identify what people have identified as triggers just by observing and tracking symptoms.
- This test aims to work by measuring white blood cell reactions to certain foods through flow cytometry.
- No published studies in peer-reviewed journals.
- While flow cytometry is solid science, the company that manufactures this test doesn’t make data available about the sensitivity ranges or predictive values.
- Food extracts are injected intradermally to provoke symptoms that patients report having when they consume certain foods.
- After injection, a “neutralization” injection is given.
- When this testing was studied, there was no difference in the “reactions” patients had when injected with suspected food triggers versus being injected with saline.
- Hair samples are checked against a database, and scores over 85% indicate a sensitivity or intolerance.
- No information on how this database was created is provided.
- In 9 subjects who did not have food intolerance, 2 samples from each subject were sent to 3 different labs that perform hair analysis. The results were different in samples tested at the same lab, as well as samples tested at different labs.
- This means that this testing has low reproducibility and low diagnostic value to actually determine which food intolerances are present.
- The patient holds a vial containing one food, while a practitioner tries to push down their extended arm. If there is weakness, this demonstrates a sensitivity to the food being tested.
- In a study where people held out a known toxin or saline, weakness was seen in the toxic substance 53% of the time, or about what you would expect with 1/2 odds.
- Definitively not scientific. It is, however, free, if you want to have your friend do it.
- Patients hold an electrode in their hand, and another is placed on their body. Attached to this circuit are glass vials containing potentially irritating foods. The resistance of the skin on the circuit is measured.
- 3 different studies show that this, like other food sensitivity tests, doesn’t work to distinguish between people with known sensitivities and those without, nor does it accurately distinguish between allergens and saline.
Unfortunately, it doesn’t seem like there’s an evidence-based way to test for food sensitivities. I’m bummed too, y’all.
But why would I feel better when I avoid foods marked on a food sensitivity test?
So if all food sensitivity tests are bogus, why do people feel better after them? This time, science does have an answer. I had an IgG test, the LEAP/MRT test done in college. I went to a Registered Dietitian for help on the suggestion of my gastroenterologist, hoping that dietary changes would help my stomach problems. I did legitimately feel better, but I’m fairly certain I’m not actually sensitive to all of the foods that I “reacted” to through this test. Here’s why.
To note: (The Commission on Dietetic Registration has since discontinued their support for this test due to the lack of evidence-based information regarding its ability to diagnose food sensitivities.)
Most IgG tests work by having you eliminate all foods that elicit any positive result, and you will gradually add foods back to your diet a few days at a time. Usually, because people have high numbers of foods they’re sensitive to, this allows them to narrow down their diet, and reintroduce potential triggers.
While this method is super helpful to understand when food intolerance arises, the thing is —you don’t need any testing to take on an elimination diet.
Food sensitivities and functional gastrointestinal disorders
For a lot of people with functional gastrointestinal disorders, they end up going through a ton of tests, many of which come back inconclusive. This is a fairly common issue I’ve come across in having IBS—there isn’t a biological marker that can be used to diagnose it, so a lot of people (including doctors) test everything to rule out all other possible causes of similar symptoms.
Unfortunately, this increase in testing does not always equate to a better diagnosis or treatment, as in most instances (98% of cases!), diagnosis can be made by which symptoms are present. Not to mention, the cycle of constant testing, waiting, and paying is exhausting.
Diagnosis by symptoms is called the Rome IV criteria, an evidence-based approach to the diagnosis of these disorders based on both the type and frequency of symptoms.
Once diagnosed, there is a clinically-validated elimination diet that helps with the gastrointestinal problems most people who take food sensitivity tests are seeking to eliminate. This is the FODMAP diet, and it relies on eliminating fermentable saccharides and polyols from the diet.
The good news is that this diet has been shown by multiple studies to significantly decrease abdominal pain, bloating, flatulence, diarrhea, and constipation. The bad news is that this diet can be hard to follow.
You don’t need to be diagnosed formally with IBS to try out the FODMAP diet, and it can be a great starting place for determining food sensitivities. A guide to the diet is linked here, as well as an infographic below on the main foods allowed as part of the diet.
Do at-home food sensitivity tests work? (And are they worth the money?)
As we learn more about the incredibly complex human immune system, maybe someday we will get to the point where at-home food sensitivity tests work and can tell us with incredible accuracy which foods don’t agree with our bodies. I really, really hope this happens.
Right now, if I were talking to college-age me, I would tell her to save the $200 on an at-home food sensitivity kit. The science just isn’t there, and knowing the myriad of other factors that can impact the GI tract and cause functional GI disorders, food sensitivities may only be one factor responsible for symptoms.
Although I followed religiously the list of “sensitivities” that contained everything from pork to raspberries, I ultimately realized that anxiety was the underlying cause of my GI issues. Keeping track of all of these “no” foods and worrying about one accidentally getting into my food only contributed to my anxiety, and made my gut issues worse.
I’m happy to say that I am now able to eat nearly everything with a fraction of the GI problems I once suffered. My only trigger food seems to be dairy, so I avoid that, and put my focus towards my mental health instead rather than micromanaging my diet.
There is likely some biological cause of food sensitivities, and there’s likely a biological cause for the relationship between mental health and functional gastrointestinal disorders. I can’t say for certain what those may be (I hope we figure it out), but I do know now that all the time I spent on figuring out trigger foods would have probably been better spent in therapy.