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The Elimination Diet A Foolproof Way of Diagnosing Food Intolerance

by Linda Gamlin(more info)

listed in allergy testing, originally published in issue 34 - November 1998

First things first: let’s be clear about what food intolerance is, or rather, what it is not. It is not food allergy (and it does no one any good to confuse the two conditions).

Food allergy is an all-out reaction by the immune system against food. The symptoms are usually centred on the mouth, lips and tongue, and although some people have nothing more than an odd tingling sensation after eating certain foods, for others the symptoms are very violent with swelling around the mouth and throat, and a sharp drop in blood pressure that produces general collapse and can be life-threatening.

This frightening reaction is known as anaphylactic shock. Except in a few rare cases, it comes on within minutes of tasting the food. Sometimes just inhaling a few airborne molecules of the food will provoke the reaction – several airlines have now banned those little complimentary packs of peanuts that come with the drinks so that passengers who are allergic to peanuts can fly without fear of an anaphylactic reaction.

Food intolerance is nothing like this. It comes on much more slowly after eating the food for one thing, and the foods to blame are often those eaten very regularly, such as wheat or milk, so that the symptoms from one meal tend to overlap with those from another meal. Most sufferers are unwell all the time because of this overlap and it is far from obvious that food is at fault.

Compared to food allergy, the symptoms of food intolerance are both less dramatic and far more diverse. No two patients are exactly alike, which is one reason why conventional medicine has trouble diagnosing food intolerance – or even believing that it exists.

The symptoms often include one, two or more of the following: headache, migraine, bowel disturbances, nausea and indigestion, joint pain, fatigue and a general feeling of vague ill-health. Occasionally there are other effects, such as recurrent mouth ulcers, stomach or duodenal ulcers, asthma, eczema or urticaria, rhinitis (a constant runny or blocked nose), glue ear, aching muscles or oedema. Some cases of Crohn’s disease and rheumatoid arthritis are attributable to food intolerance. Finally, mental problems such as depression or anxiety can be due to food, and some children with hyperactivity have food intolerance.

The important point to remember is that every single one of these symptoms and conditions can be caused in another way (although the constellation of headache, joint pain and diarrhoea is highly characteristic of food intolerance).

So the first step in diagnosis is to show that food intolerance is indeed the cause of the symptoms, and the second step is to identify the foods concerned – again, everyone is different in the foods they react to.

The first step really matters. One of the problems with the non-dietary diagnostic tests that are advertised – such as those using samples of hair or blood, those using pendulums, Vega testing, pulse testing and applied kinesiology – is that they start with the second step. In other words they assume that food is the problem. It is my strong impression that anyone who undertakes such tests invariably tests positive, and that they are always told that several foods are the problem. By contrast, when a group of people with a problem such as irritable bowel or migraine or rheumatoid arthritis undertake an elimination diet, a certain proportion find that they simply do not have food intolerance, while others find that they are intolerant of one food only. This alone shows that the other tests are producing a lot of false-positives: positive findings when no true reaction to the food exists.

This has been confirmed by objective testing of the methods. Such testing always finds inconsistencies and inaccuracy. Sending off two blood samples from the same person is a classic way of checking out such tests: two completely different lists of foods is the usual outcome. Worryingly, objective trials also show that the tests produce false-negatives: no reaction to a food in a patient who is genuinely intolerant of that food.

Various doctors have experimented informally with these testing methods, and the general conclusion is that some of them (such as the pulse test, applied kinesiology and the cytotoxic test using blood samples) can work reasonably well some of the time, but that they don’t get it right every time. Overall, they are much too unreliable and inconsistent to actually be useful. Full double-blind trials have never been carried out simply because the preliminary trials have always shown that it wasn’t worth going any further.

The elimination diet remains the gold standard in diagnosis. As Professor Jonathan Brostoff of the Middlesex Hospital in London observes ‘the patient is the best test-tube’.

The elimination diet

The principle of the elimination diet is beautifully simple and elegant.

It starts by taking away every food that could possibly cause a reaction, and returning the body to a basic symptom-free state. Then it asks the body questions – ‘Is this making you ill?’ – by offering it foods, one at a time, and listening to the answers the body gives.

Although the principle is simple, the practicalities can be much more tricky, and it is extremely important to know all about the details of elimination dieting before you begin. Different foods need to be tested in different ways, for example. And it is particularly useful to know about the things that can go wrong during the testing period, so that the procedure can be adapted if necessary. Furthermore, the answers that the body gives can sometimes be confusing, but with a good understanding of food intolerance these complex answers can be interpreted correctly.

If you want to carry out an elimination diet for yourself, it is vital that you really know what you are doing. Doing an elimination diet badly is not just a waste of time: you can alter your reactions to foods and acquire new sensitivities which make it very much more difficult to do the diet a second time. Be warned: this is something to be done only once and done very well.

The description that follows can only be an outline: explaining all the intricacies of an elimination diet is way beyond the scope of a magazine article. You also need to know about food families, food labelling, the risk of acquiring new sensitivities, and a variety of other topics to do the diet well and maintain your improved health afterwards. If you are intending to do the diet for yourself, then please obtain a copy of The Complete Guide to Food Allergy and Intolerance, by Professor Jonathan Brostoff and Linda Gamlin (published by Bloomsbury at £6.99) which will tell you everything that you need to know. Clearly this is even more important if you are intending to guide other people through the elimination diet.

The exclusion phase

During the first part of an elimination diet you exclude all the foods that you normally eat. Most people are familiar with this as the ‘lamb and pears’ diet. In fact that diet originated in America where both lamb and pears are rarely eaten foods. In Britain, intolerance to lamb is not uncommon because, with all those sheep wandering around on our damp green hillsides, lamb is actually eaten quite often.

There are various exclusion phases more suited to the typical British eater, and less difficult to follow than lamb-and-pears. Any exclusion phase that consists of only two foods has intrinsic problems because what is vitally important at this point is that you do not eat too much of any one food. The danger is that you will become sensitive to anything you eat in large quantities every day. Clearly, if there are only two foods you can eat, you must be eating those to excess or else going very hungry.

In all cases, the exclusion phase should be adjusted to suit the individual. It is very important to cut out all foods that have previously been eaten regularly, and to consume only rarely-eaten foods.

If you are a real perfectionist, an exclusion phase consisting of foods that have never been eaten before should be chosen. This can be an expensive but interesting exercise in sampling exotic foods such as yams, cassava and sweet potatoes.

During the exclusion phase, which should last 7-10 days for most people, there may be a complete and dramatic clearance of symptoms. If this occurs, then food intolerance is clearly identified as the source of the problem. If not, assuming that you have chosen foods for the exclusion phase carefully, and stuck to the diet religiously, then you can be reasonably sure that food intolerance is not the cause, and end the diet there.

Some conditions, such as rheumatoid arthritis, may require a much longer exclusion phase, but there is never any need to go beyond 21 days. The dramatic improvement that occurs with relatively mild symptoms may not happen for those with a serious long-term condition such as rheumatoid arthritis, because of the past damage to the joints which cannot be quickly repaired. In this case, a marked but partial improvement is an acceptable sign of food playing a part in causing the illness.

The reintroduction phase

If someone has food intolerance, then the exclusion phase will produce a sudden and utterly exhilarating return to health. “I’d forgotten what it felt like to be well” as one woman observed. ‘It’s like getting my life back again’ said another. Those who have been struggling on for years with food intolerance are invariably amazed at what it is like to actually lose the symptoms. “Some of those things just felt like they were me, my personality – irritable, tired, anxious – now I realise it was the food problem all the time,” remarks a man in his forties who has had food intolerance for over 15 years.

Anyone who has experienced such an improvement will be highly motivated to carry on with the reintroduction phase, despite the fact that it is quite arduous. It requires a lot of forward planning, careful self-observation, and unswerving self-discipline about what passes your lips. Foods have to be reintroduced one at a time, with a space between in which symptoms can be observed.

It sounds simple, but don’t be deceived. This is where errors can easily occur. The portions have to be large enough. The interval between testing foods needs to be just right. The form in which you test the foods needs to be just right. The number of times you eat the foods – and this varies from one food to another – needs to be just right. And you need to get through it all quite quickly, before your sensitivity to the foods begins to fade. Throughout all this, you need expert guidance, which our book aims to give.

After the elimination diet

Do not be surprised if the elimination diet identifies your favourite foods as those causing the problem. Unfortunately, that is absolutely normal for food intolerance. The good news is that you won’t have to avoid it forever. After a period of time – it might be six months or it might be three years – you can usually go back to eating it again, but in moderation. There is also the possibility of desensitisation treatment, which can work very well.

Even if you do have to avoid the culprit food it will probably seem absolutely worthwhile in exchange for the freedom from debilitating symptoms such as migraine or irritable bowel syndrome.

Case history

Isabel had suffered from a variety of health problems for over 15 years.

She developed IBS in her early twenties, migraine some years later, and joint pains in her early thirties. As far as she was concerned, these were all separate health problems, and her doctor took the same view.

Eventually, after trying many different treatments without success, Isabel came across a brief account of an elimination diet procedure in a book about nutrition and health. She tried the diet in the hope that it might help with her joint pains, which were becoming increasingly troublesome, but to her astonishment all her symptoms went away. This happened within a week of beginning the diet, and for several days she felt extremely well, far better than she had for many years. Then, before she could get very far with the testing stage, various symptoms began gradually to return.

She came across an account of a rotation diet in another book, and tried that to see if it would solve the problem, but instead things deteriorated.

During the rotation diet, her bowel symptoms were worse than they had been before she began. Eventually, with the help of a treatment called neutralisation therapy, she was able to bring the symptoms under control again. She established that she was originally sensitive to wheat, oranges and milk, and that she had acquired new food sensitivities during the early stages of the elimination diet by eating too much of certain foods, such as bananas and rice. By a mixture of dietary restrictions and ongoing neutralisation therapy, she improved considerably. The eventual outcome was that she was substantially better than she had been at the outset, although she never regained the really excellent state of health that she experienced in the second week of the diet. If she had had detailed guidance about the elimination diet, and clear advice concerning the pitfalls of eating too much of any one food, she would undoubtedly have got through the elimination diet successfully in the first place, would not have developed new food sensitivities, and would have been healthier overall at the end of the treatment.

Further reading

Brostoff, J (Prof) and Gamlin L The Complete Guide to Food Allergy and Intolerance. Bloomsbury, third edition. 1998. £6.99.
Brostoff, J (Prof) and Challacombe SJ (Dr) Food Allergy and Intolerance Baillière Tindall. 1987. The principal textbook on this topic. £70.00.
Mackarness R (Dr) Not All in the Mind. Pan 1976 (may be out of print, but worth getting hold of: a classic popular book on food intolerance, particularly its psychological effects).
Rapp, D (Dr) Allergies and the Hyperactive Child. Fireside Editions, Simon & Schuster.
Dobbing, J (ed.) Food Intolerance Baillière Tindall. 1987 A series of 11 chapters by doctors with a variety of views on food intolerance: each author was able to comment on the other chapters, and these commentaries form a very valuable part of the book, giving some insight into the range of opinions on this topic.


  1. J M Faulding said..

    I think this is the best article on the subject that I have found. I knew a little about food intolerance, having read the book "Not all in the mind" MANY years ago (by MacKarness), and found that extremely educational.

  2. Damian Davis said..

    my family has ongoing issues with one of our children who has red itchy skin. the worst thing for him is egg and if he is too hot( he automatically will tell us if he eats something containing egg (but not all things with egg in the ingredients(eg egg washed pastries))). another child is starting to show some of the same traits at 3 years old. We are trying a pear & lamb style elimination but after 2 weeks there doesn't seem to be a great deal of improvement. thank you for this article. I think my doctor/ doctors are not doing enough to help us so we are having to help ourselves. all our doctors do is refer us to another or prescribe steroid creams. seems to be bad news for my family. thanks again. someone can help, I hope I can find them.

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About Linda Gamlin

Linda Gamlin writes popular books on health. She trained as a biochemist and worked in scientific research before turning to writing. An expert on allergic diseases, she also writes about evolutionary biology, the immune system, the impact of diet and the environ- ment on health, the relationship between alternative and conventional medicine, and the role of the mind in health and sickness. In 1994 she won the Rhone-Poulenc Science Book Prize, junior category, and in 1995 The Golden Trilobite Award of the American Paleontological Society.

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