I have had so many new patients call me after they have been struggling to pull the foods listed on a food sensitivity panel – trying to figure out what they can eat. They come into my office and show me their lab, which is covered in red lines showing reactions to just about everything. What they always say to me is, “The test shows that I am reacting to everything that I am eating.” So, does it make sense to pull all the foods that a food intolerance test shows that you are reacting to? Do these tests have any validity?
Let me first distinguish between a true food allergy and a food sensitivity, or intolerance and discuss what they are testing.
Food allergies are reactions to the proteins that are in food. A true allergy is an IgE mediated immune reaction. IgE stands for Immunoglobulin E mediated reaction – you get exposed to a protein in a food and your immune system is triggered to mount an IgE response. The response can be either acute (immediate) or a delayed reaction. An IgE immune response causes a release of chemicals in the body called histamines or leukotrienes, which trigger an allergic response with symptoms like rashes, mouth tingling, mouth or skin sores, itchy skin, swelling, wheezing and full blown anaphylaxis.
People usually know what they are allergic to. They know what makes their mouth tingle or bring on a mouth sore and they definitely know what might cause an anaphylaxis reaction. Food allergies are tested by a skin prick test, where the skin is exposed to various food items and then monitored to see if a reaction occurs – welt or redness.
What people are often less clear about is whether they have a food sensitivity or intolerance. Some labs are using blood to test for an IgG reaction (Immunoglobulin G) reaction. This is a different antibody mediated reaction – it is an IgG reaction versus an IgE reaction- and it does not result in a histamine or leukotriene release. The IgG immune reaction supposedly measures exposure of incompletely digested food proteins that have crossed the GI tract and entered the blood stream. When an indigested protein enters your blood stream, the only defense that your body has at that point is to mount an immune defense. So the IgG test is looking for antibody-antigen markers for specific food proteins that have entered your blood stream.
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Do I think that people have food intolerances that are contributing to inflammatory, neurological, pain, autoimmune and digestive disorders? Unequivocally YES! I see this every day. It is my job to help people figure out what they are reacting to. Do I think that we can accurately measure food intolerances with an IgG blood test? NO! We can’t.
Unfortunately there is little to no evidence of the efficacy of these tests being used to identify food intolerances. NO evidence. IgG testing is used to diagnose certain autoimmune conditions, and demonstrate serum immunity to the measles, mumps and rubella or hep B or even chicken pox, but no validated studies on this testing, as it applies to food intolerance testing, is available.
Now, you know from my blog – I do not always agree with the stances of our various US medical associations, BUT the US is not alone in this stance. Associations and societies of immunology and allergy from various countries also state that there is no evidence of the validity of IgG food intolerance tests – Australia, Europe, Germany, Singapore, and the UK are among them.
Are These Tests Valid?
One research group in the UK checked out these tests (our equivalent to Consumer Reports) which claim to diagnose food intolerances through analysis of blood samples or strands of hair.
What they found is what I see clinically, so I thought that I would share this with you.
They found that:
- The tests diagnosed 183 intolerances – although the researchers actually had just one medically confirmed allergy and one food intolerance between them
- Identical blood and hair samples sent under different names to the same company produced different test results
- There was little or no overlap between test results from different companies
- The tests recommended excluding up to 39 foods – which could make it difficult to eat a balanced diet and lead to nutritional problems.
Clinically, for me, it doesn’t get much better. I have often found obscure foods showing up on the test (ones that the person has never eaten); I see false negatives, false positives, or the test shows that they react to everything.
The only clinical pearl that I gleam from seeing the test showing that they react to everything is that they their immune system is being triggered and that they likely have leaky gut which we would have found out by looking at their health history and talking about their current symptom set. What we cannot do with this information – WE CANNOT PULL ALL THE FOODS THAT THE PATIENT IS SHOWING WIDE SPREAD REACTIONS TO ON THESE TESTS – THIS WILL CAUSE MORE HARM THAN GOOD.
When you have leaky gut, you are going to have indigested proteins cross over and enter your blood stream. The foods that you eat on a daily basis are the ones that will be introduced with such frequency that the test will likely come back showing that you are reacting to everything, but this has more to do with the immune system being chronically triggered because of the leaky gut.
Here is the catch, if you pull all of these foods, over time, you could start to react to the new foods that you start to eat with frequency. This will also cause widespread nutrient deficiencies in people who are already inflamed because they are now on an extremely limited eating plan.
So, when a patient says to me, “The test shows that I am reacting to everything that I am eating” we need to change the understanding of what is going on here. They likely have leaky gut, inflamed mucosal membranes and the foods that they are consistently eating are making their way into the blood stream and the immune system is being triggered. That is why this test is showing that they are keying up on everything that they are eating.
Through a conversation with a licensed nutritionist you can easily identify which main foods you are reacting too, pull those main offenders, and lightly rotate the rest… while at the same time supporting digestion from the top down, addressing nutrient deficiencies, address the leaky gut, heal your gut and address you flora levels.
We should look at it this way – a food sensitivity is a symptom that something is imbalanced in the gut. This is what needs to be addressed!
I especially sway people away from either running these tests OR following the test results when they have a mucosal inflammatory condition – like an inflammatory bowel disease or gastritis, esophagitis or eosinophil esophagitis, if they have known leaky gut, or an autoimmune condition (because their immune system is going to be hyperactive to begin with), or if they have SIBO – these tests will be even less useful.
If you have SIBO, you should be focusing on a LOW fermentable eating plan and treating SIBO. Yes, you should pull known allergies and known food intolerance (when I eat ‘x’ food it makes my stomach hurt or gives me a headache), but trying to couple a LOW fermentable plan with the results of a food sensitivity panel will be downright disastrous. Along with the widespread nutritional deficiencies that will begin to appear, you will have less stamina, likely lose weight (not in a good way) and you will start to become even more hyper-reactive to the very few foods that you continue to eat.
The only time that I have really seen a value to running a food sensitivity panel is when a patient MUST have a lab in hand that shows them that they may have a food sensitivity and this validation gives them the motivation to finally change their diet.
Hands down, I would rather that you spend your money on a digestive stool analysis that will look at inflammatory markers, gut metabolism, flora levels and overall gut health than spending your money on a food sensitivity panel.
Angela Pifer, SIBO Guru
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