Professor Nick Read is an expert advocate for the psychological cause of Irritable Bowel Syndrome. In his article ‘Allergy: A clash of cultures’ he makes a number of statements that are quite contrary to the general understanding of allergy, immunology and the clinical art which we call medicine - and indeed contrary to my way of treating IBS patients.
…’over 50% of people in this country complain of food allergy and intolerance yet medical tests establish the diagnosis in less than one tenth of them’.
The answer is clear. Many of these people do have food intolerance but we do not have the blood tests to define which food(s) is the culprit. However, the cause can be worked out by the use of elimination diets.
As regards true immediate food allergy, specific IgE antibodies and skin tests are helpful in the diagnosis. This is not the whole story as some children have no specific IgE as detected in the blood or by skin testing yet are acutely allergic on their mucous membranes to the culprit food, for example peanut. The converse is also true in that some patients can eat peanuts in spite of having specific IgE to the peanut allergen.
What does this tell us about ‘allergy’? It shows us that the lining membrane of the intestine is the arbiter of reactions to foods. This has been clearly shown by Professor Ulf Bengtsson who examined IBS patients with ‘allergic’ reactions to foods but who did not show positive blood tests or skin tests. He showed that the fluid from the small intestine was positive for IgE to relevant foods. Again, the lining of the gut was the arbiter.
What about the clinical studies from the John Radcliffe Hospital in Oxford and Addenbrookes Hospital in Cambridge? Both Departments of Gastroenterology have shown that food is implicated in 50% of the patients with IBS (and also Crohns) and that the reactions are specific and confirmed by double blind food challenges. Elimination of the food can lead to the elimination of the symptoms not only in the gut but of the more general symptoms as well. These reactions are clearly not purely psychological or non-specific because of bowel hyper-reactivity.
Approximately 50% of the patients attending a gastroenterology clinic have IBS and 50% of those patients can be managed by elimination diets. That must reflect a huge potential saving of long term cost by the patient and of course long term saving by the NHS exchequer. The patient can then take charge of their own disease.
If the reaction of the food is to induce reproducible symptoms of IBS in a patient, yet there is no clear allergic or immunological mechanism discovered by the present means employed for clinical testing – that is not the fault of the patient, but evidence of our current lack of understanding of causality at the level of the intestinal mucosa. We do not need to know the scientific mechanism of a condition to be able to say that it exists. Patients present the questions in the clinic which doctors and scientists have to try and answer in the laboratory.
Recent data have shown a possible mechanism of post-infective IBS. Pimentel and his colleagues have shown that the small intestine of many of these patients has been overgrown (colonised) by bacteria. They have taken these observations further and given the patients specific antibiotics for one to two weeks and have shown that almost half of these patients respond beneficially. In a subsequent paper they have shown that those who respond also show evidence of eradication of the bacteria.
Patients with predominant diarrhoea show an increase in CD3 and lamina propria lymphocytes, in addition to an increase in epithelial mast cells. Patients with post-infective IBS show increased enteroendocrine cells in the lining of their gut. These findings suggest an external agent as the cause.
To label these patients with long term symptoms of IBS as psychological in origin would be to ignore this very important sub-group who could possibly be very simply ‘cured’ of their symptoms and not need as Freud (or Professor Read) might have put it – ‘the talking cure’.
‘Medically, allergy is a relatively rare condition’. This of course is not true. Current estimates of allergy problems due to inhaled allergens suggest that 20% of the population have hay fever. Is true food allergy ‘relatively rare?’ Not really when between 1-2% of children are currently sensitised to nuts and peanuts (peanuts are a legume not a tree nut). Is food intolerance ‘relatively rare’? When the literature is reviewed, the answer is no.
Of course we need to treat the whole patient and as the brain (in the skull) is hard wired to the ‘brain’ of the gut, it would hardly be surprising if the one did not affect the other.
The paper quoted by Professor Read in support of the purely psychological cause of IBS comes from the laboratory of Prof Bienenstock in Canada. He was able to induce allergic reactions in rats by Pavlovian conditioning, but only if the rats were previously allergic to that food. Rats not ‘allergised’ were unaffected by the conditioning.
What Professor Read postulates is that the main problem in the IBS patient population as a whole lies with the brain in the skull. The great philosopher Karl Popper would have much to say about that hypothesis in that it cannot be proved or even disproved. What I can test is whether the patient has an ‘external’ cause for their IBS, be it bugs in the gut, candida, food allergy or food intolerance. If they do have any of these, then our treatment regimes at least stand a chance of relieving the patient not only of their abdominal symptoms but of many of the associated symptoms such as headache, aching joints, brain fog and fatigue. It surely must be worth testing this hypothesis for such a gain.
Professor Jonathan Brostoff MA.,DM.,DSc(Med).,FRCP.,FRCPath.,FIBiol is Senior Research Fellow and Professor Emeritus of Allergy and Environmental Health, Kings College London
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