Are you thinking of having or have you had a food intolerance test?
In our latest blog post, Dr Megan Rossi, dietitian and medical adviser to The IBS Network explains why you should avoid them and what to do if you’re eating a restricted diet as a result of a test.
When it comes to diagnosing food intolerance, scientists are yet to develop a suitable test. Lactose intolerance is the exception but, so far, we only have tests that can detect Immunoglobulin E (IgE) food allergies.
However, a market of invalid tests has emerged for food intolerance testing, selling nothing but pseudoscience and lacking both scientific evidence and clinical relevance. Despite the convincing marketing claims that you may come across, it’s not worth your time, money or sanity to pursue testing for food intolerances.
Some of the common invalid tests to watch out for include Immunoglobulin G (IgG) tests, hair analysis, eye analysis (iridology) and muscle analysis (kinesiology). Many of those tests attach themselves to scientific concepts that sound convincing to an untrained, non-scientific audience.
Take for instance the IgG tests. This test involves exposing a sample of your blood to a wide range of different foods and the resulting antibody (IgG) measured, which the test claims is a marker of ‘intolerance’. Sounds pretty legit, right?
The thing is, unlike Immunoglobulin E (IgE) immune cells (remember they are typically diagnostic of IgE-mediated allergies), most of us will actually develop IgG antibodies to food during our lifetime, despite not getting symptoms. This is because IgG is an indicator of repeated exposure, not clinical symptoms.
What about breath tests?
These are backed by a sound scientific rationale and are often used to guide a diagnosis of lactose and small intestinal bacterial overgrowth. However, the results need to be interpreted with caution as they don’t always accurately predict symptoms. This means the test may be positive, but you may not have symptoms, in which case there is no need to intervene.
I know reading this can be rather disheartening for those who may have paid for and changed their diets based on such tests. But many people I see who are afraid to eat more than a select group of foods, find that this news can be truly liberating. In addition, it has allowed them to gain back the confidence to nourish their bodies with a wide range of nutritious foods.
What if you’ve had the tests, restricted your diet and felt better?
This is typically a chance finding. All the tests I’ve seen (and I’ve seen a lot) cast a wide ‘net’. The tests are not personalised to your specific intolerance, meaning they simply exclude many of the common food culprits. As a result, not only are you at risk of nutrition inadequacies but these tests encourage you to restrict foods that you may actually be able to tolerate.
So how do we diagnose food intolerances?
Dietitians follow a systematic process that I call the 3R process: Record, Restrict and Reintroduce. I have a whole chapter in my book, Eat Yourself Healthy, to help cut through the confusion. The aim is to safely guide you through the process of determining whether you have a food intolerance to some of the major suspects including lactose, gluten and wheat, that might be causing your symptoms.
Remember that any elimination diet should only be undertaken with the supervision of a FODMAP-trained registered dietitian.