What is an IgG?

IgG stands for Immunoglobulin (type G). Immunoglobulins are a class of proteins that function as antibodies produced by the immune system in response to foreign bodies entering the body. There are several different types of immunoglobulins with IgA, IgE, IgG, IgM being the most well-known.

Why do foods cause an IgG response?

Generally, foods are broken down during digestion into their component parts e.g. amino acids, glycerides etc. These pass harmlessly through the gut into the bloodstream. However, occasionally small fragments of partially digested or undigested foods are able to pass through the gut wall into the bloodstream where they are recognized by the immune system as being ‘foreign’. The immune system responds by making IgG antibodies to these foods.

Do high IgG antibody levels cause symptoms?

When a food causes the body to produce high levels of IgG then these antibodies combine with the protein in the food to form an ‘antigen-antibody complex’. These complexes are usually eliminated by other cells in the immune system. However, if the immune system is overloaded, these insoluble molecules become deposited in tissues within the body, causing chronic inflammation and the subsequent production of symptoms.

Is it possible to have high IgG levels and not experience symptoms?

Yes, some people do have high IgG levels to certain foods but do not have any symptoms at all. This is most likely due to their immune system being extremely efficient at clearing away the antigen-antibody complexes before they have chance to be deposited in the tissues and cause a problem. While it is true that certain common foods are more likely to show a positive result e.g. wheat, dairy, soya. The reason for this is that these foods are consumed on a regular basis in our diet and along with digestive issues this can increase the likelihood that the body may react to them. While an elimination diet will always be the gold standard, the benefit of doing a food intolerance test is that it will be able to quickly show which of the foods that are eaten on a regular basis, are a potential problem. In addition, the tests are able to highlight more unusual foods which a person may not have considered removing from their diet.

 

What should be considered before testing – What is the lower age limit for testing?

Cambridge Nutritional Sciences (CNS) existing policy for a lower age limit on testing for IgG food antibodies is that we do not recommend testing on children under the age of 2 years. We base this on the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition Guidelines for the Diagnosis of Coeliac Disease 2012, which states that there is a possibility of false negative results occurring in infants younger than 2 years of age. This related to the fact that the infant gut is more permeable than that of an adult coupled with immature mucosal immunity that is still in the learning and development stage. We have used this criterion as antibody measurements in Coeliac Disease are comparable to food IgG measurements used in our food intolerance tests. However, we are aware that there are in fact no published guidelines that specifically indicate a minimum age for testing for such IgG antibodies, for example the guidelines for testing for coeliac antibodies indicate that such testing can be performed any time after the introduction of gluten into the diet. Therefore, where such requests are received from a statutory regulated professional the decision of when and what tests to perform will remain the responsibility of the requesting clinician.

Why test for IgG antibodies to foods?

The efficacy of a diet based on the measurement of IgG antibodies specific for food components has been demonstrated in a number of conditions, both in independent studies and clinical practice. Excellent results have been obtained in patients with migraine, IBS and obesity.

How does the test work?

Food extracts are ‘printed’ onto nitrocellulose ‘pads’™ on a glass microscope slide, together with calibration standards and controls. A blood sample provided by the patient is diluted and dispensed onto each printed microarray. Food IgG antibodies, if present, bind to the food extracts and the results are measured by a high-resolution scanner, before being calibrated against the standards using the FoodPrint reporting software to give quantitative results. This software then produces a tailor-made printout of the final food IgG antibody result for each food on the requested food panel.

What is the difference between FoodPrint and Food Detective – Do they use the same technology and how does the accuracy compare between the two tests?

The Food Detective is a self-test food intolerance test which uses ELISA technology to detect the presence of IgG antibodies to 59 common foods. There is no need to send your sample off to a lab as the test can be carried out at home giving results within 40 minutes. The test will show results, as blue spots if positive and includes a control to identify whether or not the test has been performed correctly. The FoodPrint is the name of our comprehensive laboratory service and requires samples to be sent off to the lab, where they are analysed and results returned within 10 working days. The technology is more advanced than that employed by the Food Detective, as it uses microarray technology which enables a more sensitive test to be performed. Due to this, a greater number of foods can be tested and we offer a choice of 7 panels. FoodPrint 40, 60, 120, 200, vegetarian, vegan, herbs and spices, as well as an Indicator test. The Indicator test provides a positive or negative response and will require an upgrade to a larger test if the result comes back positive, in order to identify which foods are causing.

What are the sample requirements and test turnaround?

A pin-prick blood sample is required. Results are available within 10 working days.

 

Sources Cambridge Nutritional Science