Food intolerance testing – the facts

From so-called nutritional experts to celebrities with no qualifications in diet to previously unknown food bloggers, everyone seems to be talking about what you should avoid eating and what the latest thing to eat is. None of this is usually based on science but becomes popular anyway. It’s become the norm for nutritionists/nutritional therapists and other complementary therapists to offer food intolerance testing. You can also buy off the shelf kits that you send away to companies who claim to be able to test for intolerances.

What is the difference between an allergy and a food intolerance?

An allergy is your body’s immune system reacting to something you’ve been exposed to. The part your body reacts to is called an allergen. Your immune system releases histamines which can end up causing anything from a rash, swelling, wheezing, anaphylactic shock or death. The number of people who react to allergens is actually small.

More often, people have what is called non-allergic hypersensitivity, what we usually call an intolerance. Your body reacts to an allergen, but the immune system isn’t involved. It’s not life threatening, but can be uncomfortable.

How do you become allergic to certain foods?

When you’re a baby, you start becoming exposed to different food allergens. Usually, if you’re going to have a food allergy, you don’t react the first time you’re exposed. What often happens is that you become sensitised to the allergen and at a later point, if you are exposed often enough to that allergen, you may get an allergic reaction when the immune system reacts.

What happens inside your body to make you allergic?

While your body is being sensitised to an allergen, your white blood cells create antibodies called Immunoglobulin E (IgE). If, after you’ve been sensitised, you are exposed to an allergen again, the IgE antibodies cause an immune reaction.

Can you be allergic and not know it?

Yes you can. You can become sensitised to an allergen but never have an allergic reaction. This is called latent allergy and it’s not dangerous. Most people who have a latent allergy aren’t aware of it, unless they get tested for it using a testing method to test for IgE.

What is a food intolerance?

To digest food, you need the right amount of a certain enzyme to break down food. If your body doesn’t produce enough of this enzyme, you may feel bloated, have wind or get diarrhoea. This is your digestive system reacting, not your immune system. This is called an enzymatic food reaction.

There is another type of food intolerance where you react to certain chemicals in foods, which can be naturally occurring (e.g. caffeine) or food additives (e.g. sulphites). This is called a pharmacological food reaction.

How do you test for an allergy?

Doctors and qualified medical health professionals test you to see if the IgE antibodies are present for the allergen they suspect you may be allergic to. They will take a history from you beforehand to try to work out which food may be causing the problem. This, along with the test, gives them the result. There are two tests that are most often done to check for food allergies. These are the skin prick test and the Specific IgE Blood Test.

If IgE antibodies are not present for a particular allergen, you probably don’t have an allergy. If you do have IgE antibodies, it just means that you have been sensitised to the allergen but are not necessarily allergic. That’s why the doctor will take a full history. The tests can only show part of the picture.

What other tests are there?

This list contains some of the types of testing available from complementary therapists. None of them are based on actual science and have no proven value.

  • Applied Kinesiology
  • Measuring the pulse (also known as Auricular Cardiac Reflex)
  • Hair Strand Analysis
  • Cytotoxic Test (examining the white blood cells)
  • Vega Test
  • IgG or IgG4 blood tests
  • Some therapists truly believe they are providing a valuable and accurate test. For others, it’s just a way to make extra money. Making a living as a complementary therapist is not always easy. There is a lot of competition and, in my experience, most therapists offer a variety of therapies. The lack of regulation in the complementary therapies industry means tests that are not proven to be accurate can be offered by therapists who have completed short courses and who are not health professionals.

    Just because a shiny leaflet has what sounds like a plausible explanation of their testing, doesn’t mean it’s based on proven science. Tests based on unproven theories may end up diagnosing non-existent illnesses. You may be told you have an allergy or intolerance caused by chemicals, pesticides, electromagnetic radiation, preservatives, Candida, medication, hormones, leaky gut syndrome, wheat, yeast, sugar or coffee.

    What’s the harm in alternative testing?

    You may be encouraged to change your diet to exclude certain foods that you are told you have an intolerance or allergy to. The foods you eat contain nutrients and micronutrients that, if removed from your diet, need to be replaced. Often, therapists will tell you this, but then attempt to sell you supplements to replace the missing nutritients or suggest herbal remedies to treat you. If you can’t afford to buy the supplements but remove the foods from your diet unnecessarily, you may end up with a deficiency.

    The main fads right now are gluten free and dairy free diets. Dairy contains calcium and if you cut it out completely and don’t ensure you are getting enough calcium, you risk getting fractures. Cutting out gluten if you don’t have a gluten intolerance doesn’t make you healthier. Again, you may be missing out on important nutrients.

    What is the IgG or IgG4 Test?

    I’ve seen this test being offered quite a lot lately, so I am concentrating on this rather than the others.

    This test measures your body’s reaction to IgG or IgG4 antibodies in foods. There are four subclasses of IgG antibodies, which is why IgG4 is sometimes tested. When you eat, you develop IgG antibodies to allergens, which is a normal response that shows you’ve been exposed to that food but not that you’ve been sensitised to it. What the IgG response does is protect you and stop you developing the IgE allergy by remembering to suppress a response when you eat that food again.

    Imagine your body is like a computer. You eat a certain food and your body makes a little code so next time you eat it, it already knows how to respond. You’ll either get the IgE code if it doesn’t want to accept that food again and then you’ll have an immune response or it will get an IgG code to say, that’s okay, I’ve had that before, I know what it is and you won’t have any reaction to the food.

    The companies selling IgG blood tests and the therapists offering them may tell you that IgG antibodies are linked to delayed food sensitivities and chronic symptoms. They may tell you that IgG-based diets that exclude certain foods will help relieve chronic illness. What they don’t tell is that it’s been shown that having these IgG antibodies is simply a sign of exposure to a food and tolerance of that food, not that you shouldn’t be eating it.

    If you get tested for IgG levels, you may be told the levels are high for certain foods. There is no accepted level, so there is no high, medium or low level. Everyone will have a different level. It depends on various things, like how much of that food you’re eating and possibly how you were fed as a baby. Based on levels of IgG, someone who is perfectly healthy will get the same diagnosis as someone who has symptoms. This makes no sense.

    The most common allergens are wheat and milk. You wouldn’t be having an allergy or food intolerance test if there was nothing wrong with you, would you? So, if you get advised to exclude wheat and milk after an IgG test and you feel better, you will most likely believe the test was correct.

    If I have a food intolerance, what’s the best way to work out what it is?

    Elimination diets have been successfully used to work out what foods are causing symptoms. An elimination diet is done over several weeks where you start with a very plain diet to stop any symptoms and then introduce one new food. If that food causes a reaction, you make a note of it and go back to the plain diet until your symptoms go away. Then you introduce another food. This goes on until you’ve worked out what you are sensitive to. Apart from milk and wheat, eggs, tea, coffee and oranges commonly give symptoms. Make sure you see a registered dietician before starting an elimination diet to make sure you are doing it right and to get proper medical advice.