Although classical IgE-mediated food allergy is rare in adults with IBS, some studies have shown that circulating IgG antibodies to a range of food proteins are increased in about 50% of patients with IBS; much more than in healthy subjects1,2. This suggests that the permeability of gut is increased, raising the possibility that undigested food proteins could be responsible for the inflammation and hypersensitivity observed in many patients with IBS, especially those with diarrhoea.
About 20 years ago, YorkTest developed and launched FoodScan; food-specific IgG enzyme linked immunosorbent assay (ELISA) tests for a range of food intolerances. FoodScan currently retails at £250 and YorkTest have used it to create a global business, conducting upwards of 30,000 tests per year in the UK, 58% of them for digestive symptoms
Using blood from just a single pin prick, FoodScan screens for circulating IgG antibodies to 113 different food antigens. YorkTest also offer Food&DrinkScan (reactions to 158 foods). Most people with IBS turn out to have raised food-specific IgG levels. Often a range of foods is implicated (average between 4 and 6 different foods). Many include foods that individuals frequently ingest, but reactions are also obtained from foods that are eaten less frequently. Customers are then offered a telephone consultation with a registered Nutritional Therapist who will advise them how best to modify their diet to exclude reactive foods and to replace them with foods that are equally nutritious
What do the results mean?
Normally food protein is broken down in the gut by digestive enzymes and absorbed as small peptides and amino acids. What the ELISA tests indicate is that sufficient intact food protein is getting across a leaky gut wall to generate an immunological response, attaching antibodies and an enhancers known as complement to the ‘foreign’ protein or ‘antigen’ so that it can attract white cells and be eliminated. If enough of these complexes lodge in tissues, particularly in the gut, they may cause a low grade inflammation and an increase in sensitivity. So here we might have a mechanism for the association of a sensitive gut with sensitivity and symptoms in many other organs.
If food antigens are getting in, then bacterial antigens may be getting across as well. This would explain why increases in gut permeability brought about by alcohol, stress, inflammation or changes in the microbiome have been implicated in IBS and a range of low grade inflammatory illnesses including obesity, arthritis, fatigue and fibromyalgia.
But complement activation and attraction of inflammatory cells only applies to IgG1, IgG2 and IgG3 components of the IgG system. IgG4 antibodies are regarded as blocking antibodies that prevent not only the hypersensitivity induced by IgE, which activates mast cells releasing histamine, but also the inflammation induced by other IgG antibodies. Thus, testing only for all components of food specific IgG antibodies ensures the best case for identification of foods that may be causing significant clinical reactions.
Debate ranges around whether the presence of circulating food-specific IgG antibodies are an index of specific food ‘allergic responses’ or are just markers for a nonspecific permeability of the gut and exposure to invading food antigens . If The YorkTest Programme is no more than a sophisticated method of identifying a leaky gut in sensitized people, then will it help to remove the foods implicated and if so for how long?
What is the evidence?
Some years ago, Allergy UK commissioned a retrospective postal survey of 5236 customers, who had elevated food specific IgG levels and had purchased a YorkTest Programme. 3,626 stated that they had followed the diet rigorously and 76% of those reported improvement in their condition3 though tests were not repeated to see if the IgG levels dropped after taking the diet. Patients with gastroenterological or psychological illness showed the greatest improvements and the results were noticeably better if patients had several different ailments. 92% of those who had followed the dietary changes rigorously and responded positively, reported a deterioration in symptoms after reintroduction of the implicated foods. Similar results were reported in other studies4-6. These data look compelling – at least as good as other results for dietary management of IBS. Patients, however, knew they were receiving dietary advice based on their test results – they believed they were getting the right treatment and they felt better. Nevertheless YorkTest claim this targeted dietary intervention for non IgE mediated food allergies avoids the laborious and time consuming trials of dietary exclusion.
‘There’s nothing so good or bad as thinking makes it so’. Many people with food intolerance have no evidence of a specific biological reaction to a component of food7, and may instead have a psychological aversion. It is for this reason that clinical scientists carry out double blind randomised controlled trials of treatments.
The most positive and rigorous study involving YorkTest and IBS was reported in 2004 by Professor Peter Whorwell’s team in Manchester in collaboration with Dr Tim Sheldon from the York Consortium8. This was a double blind randomized control trial in 150 patients with IBS that compared the effects of an exclusion diet based on the results of the YorkTest with a sham diet. The latter attempted to match the exclusions in the ‘true’ diet by excluding staples and other foods that did not show an antibody response. IgG titres were elevated to between 1 and 19 different foods (average = 6.5) – not so much different to the range of foods implicated in previous studies of food intolerance9. The most common foods identified were milk and yeast (89%), with wheat and egg also showing a positive result in about half the patients. Not all patients were fully compliant with the diet and there were a number of drop outs, but overall, there was a statistically significant 10% reduction in symptom score with the true diet versus the sham, rising to a 26% reduction in patients who were fully compliant. Relaxing the diet resulted in a deterioration in symptom score, which was greater in those on the true diet. This trial is as good as it gets for most dietary interventions. The only serious criticism is that it would have been impossible to conceal the nature of the diet. Many patients would have had preconceived ideas on what foods upset them and since a large majority would have been told to exclude milk, egg and bread, all of which have been implicated in food intolerances and allergies, we cannot exclude the powerful effects of the patient’s belief and their desire for relief.
A Controversial Issue.
This trial and others have excited a good deal of controversy. Negative pronouncements have been issued from The European Academy of Allergy and Clinical Immunology, the American Academy for Allergy, Asthma and Immunology and the Australian Society for Clinical Immunology and Allergy largely on the grounds that high IgG4 antibodies are found in healthy subjects and may indicate exposure to food antigens rather than allergy or intolerance10. Even The House of Lords Select Committee on Science and Technology (see 8.35 to 8.40) were critical of The YorkTest Programme.
But let’s not prejudge the issue based on those responses. There is so much that works in medicine that we don’t understand, and some of the studies on YorkTest do seem impressive. The most damning indictment would seem to come from a recent large case control study from Norway, which failed to show any difference in food related IgG antibodies between IBS Patients and a sample from the general population11 But might this be predicated on either the antigen load and antibody titres or whether the gut in IBS is already sensitised by fears about certain foods acting through the brain gut axis. As Professor Robin Spiller from Nottingham University expressed recently, ‘I feel the immune activation in IBS is for most subjects more related to brain gut interactions which activate mast cells by nonimmune mechanisms’ (personal communication).
Diets for the sensitive guts of people with IBS based on multiple sensitivities can always risk nutritional deficiency if taken to extremes. Exclusion of foods that might excite the immune system in a leaky gut as well as the fats and FODMAP foods that trigger symptoms in a sensitive gut could pose a serious problem unless monitored by a dietitian trained in food allergy or intolerance. No milk, wheat, fruit, vegetables, fatty foods, dairy, red meat etc; where would it stop? And wouldn’t the anxiety over what food they can eat just add to the sensitivity of the gut? Is there another way? In recent months, the FODMAPs team at Monash University, Melbourne have become less restrictive, suggested that most people with food intolerance might respond to restriction of onions, pulses and some fruits. They have also announced the launch of a project to investigate zonulin, the protein that closes the tight junctions in the gut and makes it less leaky. Some probiotics are said to heal a leaky gut.
So, is the YorkTest worth the money?
After 20 years, the interpretation of the YorkTest Programme is still not clear. The evidence is suggestive but nowhere near conclusive. Nevertheless, according to YorkTest’s own data, the results of the antibody tests are reproducible and most people get better on their targetted exclusion diet.
But there’s a more philosophical issue. You could argue that it really doesn’t matter as long as it makes you feel better. There are so many decisions in life that we make on the basis of what feels right for us: the car we buy, the apartment we rent, the gym we go to, the complementary therapies we choose, the clothes we wear, the shampoo we use, the toothpaste we brush your teeth with, the way we will vote in the EU referendum, even the person we marry. How many of these decisions are made on the basis of convincing evidence? If you were to examine the evidence for every decision you make, you would never do anything. So if you believe in the YorkTest programmes and they results seem to reassure you and improve your symptoms, then this could be money well spent.
All that organizations such as The IBS Network should do is to inform you of the nature of the evidence on the YorkTest Programme and point out the risks for your own nutrition and health of adopting a diet that restricts too many foods. But if you do decide to embark on this course, you would be well advised to seek guidance from a registered dietitian, trained in treating food intolerance.
Have you taken a YorkTest Programme? Did it help? Do tell us.
My thanks to Dr Gillian Hart from YorkTest, Professor Robin Spiller and IBS specialist dietitians Julie Thompson and Marianne Williams for their advice in the preparation of this post.