Welcome to episode 75 of the Inside Knowledge podcast for people with IBS. I’m Anna Mapson. As a nutritionist working with people who’ve got IBS, I have spoken to hundreds of people looking for cures for their digestive issues. And if you’ve been searching online, you may well have been marketed a food intolerance test to try and find the cure for your digestive discomfort, bloating, pain, erratic bowel movements.
Of course, you’re going to try all the things you can, look at all the options to try and uncover a the problem that is leading to these horrible symptoms. The food intolerance testing companies are very good at identifying people who are looking for these kind of solutions as well. And so once you have started investigating digestive symptoms, you will often be marketed, these kind of products.
IgG food intolerance tests
The type of food intolerance tests I’m going to go into today include IgG blood tests because these are the ones I find people most commonly do. They are the easiest ones to find. They seem a little bit science y as well. Because someone’s analysing your blood. So that’s also an important factor for many people thinking, well, it must be scientific, it must be medically valid.
Other tests to avoid
Other tests you might have seen on the market include tests, analysing your hair to identify food intolerances. Vega testing, which I think includes passing a small electromagnetic pulse through your body and looking at changes in your electromagnetic field, I’m not sure. Kinesiology, where you hold a small amount of a food in a glass jar on your body, and then they look at your muscle response.
So these are again, not based in any science, and I would definitely not recommend spending your money on identifying food intolerances through those kinds of methods either. I will come on to a bit at the end what you can do. And how you can start to address your food issues, or maybe you don’t have any food issues. Maybe it has other things, but if you want to start looking at your diet then we can definitely come to that at the end of this episode.
Food allergy vs food intolerance
Now first up, I just want to talk about the difference between a food allergy and a food intolerance. I know my IBS clients feel utterly awful when they eat certain foods. You get such bad bloating, gas. You feel like your constipation is triggered. Maybe you get stomach pain and that makes you think you’ve got an allergy to a certain food.
In the UK, Allergy UK estimate between 1 and 10 percent of adults and children have some kind of food hypersensitivity. But around 20 percent of adults believe that they’ve got a food allergy. More people think that they’ve got a food allergy than people actually who do. But it doesn’t mean that you don’t react to food.
Food reactions
We know that people do react to foods that they eat and certain meals really can trigger these uncomfortable, painful, and sometimes embarrassing digestive symptoms. Food intolerance can show up in lots of different ways. And I’m absolutely not saying that food intolerance is not real. It’s just that the way that we can test for them, and the problems that we have with identifying them, are not solved by taking an IgG food test. Food intolerance can be caused by lots of things.
Visceral hypersensitivity
It can be gut brain hypersensitivity, so that you have like an Overactive nervous system in your gut, really feeling every little twinge, every pain, and sending overly hypersensitive messages back to your brain about the state of your digestive system. That can be really common in people who have IBS visceral hypersensitivity.
Enzyme deficiency
It may be that you have a lack of certain enzymes that break down foods. Commonly we think about lactase, which is breaking down lactose, which is the sugar in dairy product. The production of this enzyme can be damaged in our gut due to either things like SIBO, bacterial overgrowth in the small intestine, can be genetics, and the same kind of thing with fructose malabsorption as well. Sometimes you’re just not absorbing it in the way that you were before. These kind of food intolerances can be quite common.
There is a small population of people who are also sensitive to gluten which is called non coeliac gluten sensitivity. And then there are a very small subset of people again who have a sensitivity to other compounds in food such as histamine or salicylates.
How food allergy differs from IgG intolerance
So all of these are real problems that can cause all of the symptoms that you might be getting with your IBS. The way that food allergies are different from, a non allergic response to foods is down to how our immune system responds to the foods. So a food allergy is normally an immunoglobulin E, so that’s IgE mediated allergy.
That just means that an antibody, called IgE, is produced by your immune system when it encounters the allergen. These commonly are things like the protein in eggs or milk for example. The reactions are pretty immediate so normally within three hours of eating them. Think about people who are allergic to peanuts for example they will get an almost instant allergic reaction and these can be utterly life threatening, very very serious.
You can also get non IgE. mediated allergies and this might be to things with dairy for example, and you’ll get an eczema flare up a bit later. Again, that’s a an allergic reaction and it’s different to a food intolerance.
IgG food intolerance?
The difference with the IgG food testing is it’s measuring immunoglobulin G. So this is IgG. Again, another antibody, something our immune system makes in our blood when it encounters an antigen. An antigen is just something that the body needs to deal with. It could be a virus, a bit of bacteria. And in our normal digestion, the food that you eat is broken down by our enzymes. Like lactase, we just talked about. We also have lipase, which breaks down fats.
And it’s thought that we actually produce IgG antibodies to foods that we eat the most, which is why you might see things like dairy, eggs, and wheat often showing up on these IgG tests. Positive IgG test results are expected in normal healthy people as well as in people who have got a health condition such as IBS.
Are IgG tests measuring the right thing?
When we think about whether IgG testing is valid for food intolerance, It’s important to know, what is it we’re actually measuring? Like, what is the food that is actually being tested? Are they testing raw or cooked chicken? Is it raw or cooked egg? And are we talking about egg yolks or egg white? These are very different compounds.
Like, are you measuring a protein like an amino acid? Or are you measuring a type of carbohydrate? That has got a big impact on our digestion. And often, the food intolerance that we have, This test will just give you an overview of the food without being very specific.
Is the test specific?
We also want to know, when we’re thinking about whether a test is valid for condition, is, is the test specific? Because there are four types of IgG. Which subclass of IgG is actually being measured? And is the company being specific about that? That allows you to see whether the same test could be replicated in different labs. If it is a clear test explaining exactly what food they’re testing, exactly what IgG antibody they are testing, then you should be able to get the same result replicated when you take the same test at different labs. Because they should all be testing the same thing.
Is this marker clinically relevant?
Then we also want to think, does this marker actually have an impact on my health. So if IgG is high, does it mean my symptoms are bad? Those four things to consider are really important when you want to understand whether the IgG tests are accurate.
The other issue we have as well is that there is no regulation of IgG testing. So it’s difficult to be sure how good the lab is. We don’t know necessarily whether they’re all doing the test to the same standard, what their, methods are like. They generally do not publish a lot of this information, so it’s very hard to compare.
What does high IgG mean?
As I said, an IGG is Antibody and normally they’re measuring IgG4. That is the one that shows, you’ve eaten a food normally in the last 60 days. In the last two months, you’ve probably eaten this kind of food But it may also show up in your body something that you’ve eaten a long time ago. It’s basically your immune system’s way of handling an alien product in your body, that’s in food, but it doesn’t mean that it’s a sign of hypersensitivity.
And there is actually some research that IgG is actually a marker of immune tolerance. I’ll put some studies in the show notes for you to go and have a look in a little bit more detail. And I have also written a blog about this a couple of years ago and I will also link that in the show notes which just explains all of this in a lot more detail if you’re someone who likes to read your information.
IgG can indicate tolerance to foods
As an example of how IgG can be a marker of tolerance, there was a study, it was in 2009, so quite a while ago, but, patients who had an IgE allergy. An anaphylactic response to peanuts. What they will do is try and see if tiny amounts of the allergen can increase their permanent tolerance.
Some people who have more really serious allergies to milk or peanuts will be in a medically controlled setting, given tiny amounts of the food over time to try and see if their body can learn how to create tolerance to these things that they’re actually really allergic to.
It’s a great, exciting new approach for expanding tolerance for allergies. In one of these studies, they saw increases in the patient’s IgG4 levels to those foods. They measured this oral immunotherapy to peanuts in people with a peanut allergy, and they showed that IgG increased as they were exposed to tiny, tiny amounts. The researchers actually said elevated IgG is associated with immune tolerance, not intolerance.
And that was their conclusion from that study.
Do symptoms correlate with high IgG?
If we want to now look at whether it has any effect on IBS, specifically, so moving away from food allergies, there was a couple of studies, again, from quite a while ago. 2007 is the first one, which showed that there was no correlation between symptom severity and and IgG levels.
So they did an IgG and an IgE antibody test to 14 different common foods in patients who had IBS. Now in this study what they did find is that IgG levels were higher in those patients who had IBS. And another group who had functional dyspepsia, so that’s like more the upper digestive reflux y type issues, but there was no correlation between the symptom severity and the IgG levels.
Yes, the people had higher levels of IgG, but the people who had higher levels did not have worse symptoms. And so it doesn’t really show us that having higher raised IgG actually correlates to symptoms. Therefore reducing it wouldn’t necessarily reduce your symptoms.
IgG diet vs a sham diet
In another study from 2004, they looked at a combination of patients with IBS taking a sham diet, so just taking any kind of old diet. Then the other group had a diet removing foods which had shown up a high IgG result in a food intolerance test.
We had two groups, one which did a kind of, random removal diet, and the IgG group, who were following foods removed that had been highlighted. Showed a 10 percent greater reduction in food related digestive symptoms compared to people on the sham diet. However, large proportions of the treatment group removed common high FODMAP foods.
The ones that they were removing on the IgG test were common IBS triggers such as wheat, cow’s milk, peas, cashews, and and yeast. And then the people who were in the sham diet had all of those foods in. Perhaps they had randomly removed things like broccoli or oranges or, I don’t know, peanuts or something.
So they had randomly removed a selection of foods and they had a slightly less reduction in their digestive symptoms than the people who were following the IgG led diet. But they were still eating a lot of those common IBS triggers.
Is the sham diet really accurate?
This is part of the problem that I was mentioning, that IgG will typically show up for foods that you eat a lot of, and generally you may be eating a lot of foods like wheat, milk, nuts, vegetables that could be higher FODMAP.
Blinded IgG reintroduction
And then another study took people who had had a high IgG4 positive response to a number of foods and then they blinded them to a introduction of those foods into their diet. Um, in this case, they were looking for urticaria or like skin rashes, but there was no response or no correlation between having high IgG response to a food and the symptoms.
Again, it’s another Study that shows literally no benefit to knowing whether you’ve got high IgG to a certain food. Now, as well as all of those studies and there are more which show that there is no evidence that can support the reduction of foods that you’re creating a high IgG response for. We also are missing a bank of positive evidence.
No positive evidence to support IgG testing
Often when we look at nutrition research. It’s a complex picture and you kind of need to understand. So for example, the thing that often I think about is omega 3. There are studies that show taking omega 3 is beneficial. There are lots of other studies that show taking it is not beneficial.
And it all depends on the population of who you’re testing, the amount that’s been tested, how long they took it for, how they were tested. There’s a whole load of things that we can look at that’s much more complex than testing just for whether you took a drug and whether it worked or not. It’s very difficult to compare drug testing to nutrition testing. Because of course, people are living in the free world as well. They’re not living in a laboratory.
All of these things are different factors that can influence a nutrition, outcome. However, when we’re looking at IgG testing, we don’t see that balance of positive and negative.
We just see quite a big stack of things that show it doesn’t work. And then there’s not really any evidence to show that it does work.
NHS doesn’t recommend IgG testing
And that is why there isn’t official guidance to use these IgG tests. There isn’t a strong evidence bank that says it’s worth the money, or it’s worth incorporating into the NICE guidelines, or, you know, normal NHS care. If you’re thinking, yeah, but I did a test and it actually helped when I cut out all of those foods.
Why might you feel better?
So how does that work? Well, there are lots of reasons why it could work. Sometimes it could be that the typical foods that they’re telling you to ignore are common IBS triggers. Maybe it’s things like wheat and milk and cheese. Maybe there is a sense of placebo, so it’s a sense that you’re doing something, you’ve taken action, you’re taking control, and that can be really powerful in and of itself.
Also, just any kind of change to your diet can be very helpful. Sometimes this happens when people go gluten free, for example. You start to change your meal patterns, you’re thinking about your food more. You’re more conscious, you know, you’re cutting out certain things. This could be, a load of things you’ve done before. Always having little biscuits at work, or, just changing your patterns.
Making a change is positive
Those can also have an impact on your digestive system. Sometimes making any change can have beneficial effects for the short term. It might also just have got lucky, like it might just have identified something that does cause a problem for you.
Unnecessary over restriction of foods
And actually, it could be random, and a bit of a coincidence. There are problems as well with actually stopping eating a huge range of foods. I often work with people who come bringing their food intolerance tests saying This is a big long list of foods. I haven’t eaten them for a year because I did this test and I’m too scared to trial them again. I’m still getting symptoms.
Part of the problem I see is that you cut out all of these foods and you’ve still got symptoms. It wasn’t necessarily those foods that made things worse, but also it’s the mental impact. You’re having a huge layer of restrictions. And sometimes you might have a one list from the food intolerance testing, another list that, maybe came from a FODMAP diet.
You’ve got another list of stuff that you just know has been a trigger, maybe a lasagne that you had, or that time you went out and had a cheesecake. You’ve got a whole list of ingredients that you can’t eat from multiple sources. And it’s creating so many food rules that is just really, really challenging to live a normal life and eat in a normal way.
Mental strain of restriction from food intolerance tests
There’s the mental aspect of restriction, but also, you could be missing out on really good nutrients that are important for you and important for your strong, healthy digestive system. So generally, things like fibre that could be feeding your gut bacteria, missing out on key amino acids through reduced protein intake. Different nutrients and vitamins, minerals, antioxidants that you’re omitting because you have followed this diet for so long.
It’s not without consequence to go through a restrictive elimination diet. If you listen to all of that and thought, yeah, okay, I get it. I’m not going to do a test.
I feel like I still want to do something though. What can I do?
What can I do to find my food intolerances?
Well, you could try to create a food and symptom diary.
Track your symptoms & food
So start tracking your symptoms. This isn’t helpful for everyone, but for a lot of people it really can be. Listen to episode 6 where I go through how to track for IBS. There is a lot of information in there about what data you can collect. How to do it. In the show notes for episode 6 you can also download for free my template that I use with my clients, it’s just a spreadsheet, to track what you’re eating and how you’re feeling over a number of days or weeks, and then, see what the results are showing you.
Go back and listen to that episode if you haven’t heard that. If you’re also just thinking about starting to tackle your IBS, the other thing I really suggest you do is download my non food strategies for dealing with IBS, because this is something I can confidently say most people with IBS can start with.
Before you even look at your food, I think it’s really helpful to start thinking about how you eat, when you eat, the gut brain connection, like, what kind of things can you do to try and improve your digestion without actually changing your diet. I would also really recommend you download that and start to work through that little workbook, that’s also free.
Speak to your doctor
The kinds of tests that you could look at as well with your doctor would be, a lactase test. The way they do that is through a breath test. You will drink a small amount of lactose, and then look at your breath hydrogen levels. You could ask your doctor about a hydrogen breath test for lactose.
Also that can be a fructose test to look at fructose malabsorption. You should also ask that you can get coeliac disease ruled out. That is not a food intolerance, but it is an immune reaction to coeliac disease. And do go back and listen to episode 73, where I talk about coeliac disease or IBS.
There’s lots of information there on how to get tested and all the things that you should be looking out for to make sure before you get a diagnosis of IBS, that you have actually had coeliac disease ruled out as well as other things.
Try the low FODMAP diet
And the other thing that regular listeners of my show will definitely have known is something that’s worth doing is the FODMAP diet.
So again, it’s not suitable for everybody, but for some people who have IBS, if you haven’t yet diagnosed it, been through this dietary intervention process. It is the most tested dietary interventions for IBS. It’s well researched and it’s got a lot of evidence behind it. It’s extremely challenging to do and to follow.
But, It can really help you identify particular food triggers. So the purpose of that diet is you remove certain foods out of your diet for a set period, two to six weeks. You look for improvements and then you carefully bring them back in again, monitoring your symptoms. So it’s a whole process. It probably lasts like three to four months, but can really help you identify your triggers in a sciency based way.
And it’s based on how these foods are digested. based on the understanding of how these foods get broken down in your system and the symptoms that they could be bringing up. it’s more accurate and more valid than following a diet from an IgG food test.
Please rate the show
If you found this episode helpful, please can you leave me a little review or a rating just to show that you appreciate the show.
It would really help me and I would Be very thankful. Thank you so much for listening to this episode of the Inside Knowledge podcast. Better digestion for everyone.