Food intolerance: sifting the facts from the fantasies

Judy Buttriss explains away the media hype

Just how common is wheat allergy?

Last year, a two page feature article in the Express newspaper carried the headline, "Are you allergic to bread?" The thrust of the article was that one in three people has an intolerance to wheat which causes anything from bloating to depression. Unfortunately, the headline was both alarmist and misleading. More unfortunately still, the article contained several scientifically meaningless statements, contradictions, and factual errors. There were statements suggesting that fermentation of foods in the gut is similar to "low grade poisoning," and wheat is "very hard for our bodies to digest."

The suggestion that wheat intolerance affects 35% of the population was a gross overestimate, and no scientific studies have shown the incidence to be anywhere near this high. The current estimate, based on a study conducted by the then Ministry of Agriculture, Fisheries, and Food for the total prevalence of all food allergies (including peanuts) in the United Kingdom is 1.4% of the adult population.¹ Coeliac disease is the main form of wheat intolerance and is characterised by a specific physiological pathology whereby a T cell mediated delayed hypersensitivity is triggered by consumption of the wheat protein, gluten. Coeliac disease is estimated to have an underlying prevalence--that is, diagnosed plus undiagnosed cases--of 0.3%.²

Techniques have improved

The highly sensitive techniques now available mean that it is possible to identify people with coeliac disease that had previously been undiagnosed because the symptoms were relatively mild. To the casual observer, this might be taken as an indication that the prevalence of coeliac disease is increasing. However, the reality is that a proportion of cases, such as those with mild symptoms, had simply not been picked up. Symptoms of coeliac disease classically include diarrhoea, weight loss, and malnutrition, but not the symptoms mentioned in the article, which included headache, bloating (due to fermentation), and skin problems. The gold standard test for diagnosing coeliac disease is an intestinal biopsy, which should be carried out only by a specialist clinician. Coeliac disease is usually a life long condition that requires strict adherence to a gluten free diet if complications are to be avoided.

Fermentation of indigestible components of food, such as dietary fibre, is in no way similar to low grade poisoning. Indeed this very process, which takes place in the colon of all normal people, is positively associated with good health, hence the interest in foods containing prebiotics and probiotics.

Finally, far from reducing the amount of carbohydrate rich foods, such as bread, in the diet, as proposed in the article, government recommendations are that we should obtain 50% or more of our energy requirement from such foods, which play an important part in a healthy, balanced diet. Bread is an important staple in Britain. It is rich in complex carbohydrates and low in fat. Statutory fortification of wheat flour makes it an important source of calcium, iron, and B vitamins, and hence it is a significant contributor to the dietary intakes of these nutrients. Nowadays, bread (especially white bread) is often fortified, voluntarily, with folic acid, a vitamin recognised to be of crucial importance in the protection of women against neural tube defects in their offspring. There is also growing interest in the possibility that folic acid has a beneficial role in primary prevention of heart disease and possibly some other chronic diseases.³ The suggestion that people should cut back on foods such as bread runs directly counter to government advice on the importance of a diet rich in folic acid, and the general advice concerning the importance of a diet rich in carbohydrate and fibre.

Sorting the wheat from the chaff

Only a limited number of laboratory tests are of value in helping to diagnose food allergy; other tests on hair and nails have no proved value, despite the claims often made, and can result in misdiagnosis; the unnecessary treatment of a non-existent disease, perhaps by a poorly constructed diet; or perhaps most importantly, failure to detect a real and serious health problem.

The existence of an allergy can be confirmed by the use of exclusion diets followed by a challenge (or provocation) test with the suspected food, but these tests should be attempted only under medical supervision in case they trigger an anaphylactic reaction, which requires immediate treatment with adrenaline.

Exclusion diets take many forms, the type selected depending on the dietary and medical histories of the patient and the frequency of symptoms. If a child is put on an elimination diet, even for a short period, it is important that advice is received from a dietitian to ensure that the resultant diet is appropriate for normal growth and development--that is, that excluded foods are replaced by foods with a similar nutrient profile. The principle of such diets is that suspected foods are eliminated from the diet for approximately two weeks before a challenge with the suspected foods, which are reintroduced one by one in small amounts, with the quantities gradually being increased with time.

Provocation tests can be performed as open food challenges, and as single or double blind challenges. An open food challenge is when the patient (and family) and observer know which food is being given. In a single blind challenge only the observer knows the identity of the food, and in a double blind challenge neither the patient nor the observer knows. In a double blind placebo controlled food challenge (DBPCFC) both a placebo and a test substance are administered, and the identification of both remains unknown to the patient and to the observer. This protocol is recognised as the "gold standard" in terms of confirming or refuting the presence of food allergies, as the results are far less likely to be influenced by patient or observer bias.

The use of DBPCFC tests has been validated under stringent scientific conditions, but the same cannot be said for some of the other tests that can be purchased by the public from a variety of sources--for example, pulse tests and sublingual provocation food tests.

A food challenge always carries the risk that it can trigger an anaphylactic response and so experts in the diagnosis of allergy often prefer to use skin prick tests, which use an extract of the suspect substance, or measurement of blood antibody levels (the radioallergosorbent test, or RAST). The value of skin tests is limited by the ability to obtain pure food protein extracts, which will not trigger false positive tests. Tests such as these that measure IgE antibodies are of no use for diagnosis of other forms of food intolerance, such as lactose intolerance or cell mediated immune responses such as coeliac disease. If a food intolerance is diagnosed, diet is the cornerstone of treatment and management.

Does diet during pregnancy and lactation influence the risk of allergy?

There have been suggestions that a baby's chance of developing food intolerance can be reduced if the mother restricts her diet during pregnancy or while she is breastfeeding. However, unless the prevailing view is that unless there is a strong family history of atopic disease the benefits are not convincing^4­6 It has also been suggested that restricting the growing baby's exposure to allergens is precisely the thing to be avoided. In babies and young children development of specific antibodies to environmental allergens, especially those encountered in early life, is a normal physiological response by which tolerance to the environment is developed. It may be that the tiny amounts encountered via the mother are precisely the quantities required to trigger the normal immune response--namely, tolerance.

Nevertheless, it is recognised that very young children are particularly vulnerable as they are born with an underdeveloped immune system. Consequently, as a precautionary measure, the government's advisory committee COT (Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment) has recommended that women who are atopic themselves or in families where the father or any sibling is atopic may wish to avoid eating peanuts and foods containing peanuts during pregnancy and breastfeeding.⁷ It also advised that there is no reason for pregnant and breastfeeding mothers who do not fall into this category to avoid peanuts. In addition, COT advised that infants whose parent(s) or sibling(s) have a history of atopic disease should be exclusively breast fed for four to six months and that these children should not eat peanuts or peanut products until the age of 3 years.

Is allergy the cause of conditions such as irritable bowel syndrome and migraine?

Allergic reactions to food seem to be blamed for just about every health problem going, from phlegm production to obesity, according to some sections of the popular press, but what does the evidence tell us?

With regard to irritable bowel syndrome (IBS), the picture is not clear cut. Patients present with ill defined gastrointestinal symptoms, and while there have been some suggestions that abnormal colonic fermentation and gas production may be involved⁸ and that in some patients there is mucosal inflammation,⁹ there seems to be no single explanation for the symptoms.¹⁰ For example, some patients benefit from a high fibre diet, while others claim that such a diet makes symptoms worse. In general, there has been a failure to find a positive response to dietary manipulation, and where it has been found it was a non-specific response. Furthermore, features of anxiety and depression are often reported, and may have a role to play. On the other hand, various drugs have been used successfully in the treatment of IBS.

Several factors have been associated with the precipitation of migraine, including changes in the menstrual cycle and hypoglycaemia. Features of the diet are also believed to be additional triggers: people with migraines commonly cite red wine, cheese, citrus fruit, and chocolate.¹⁰ Studies suggest that the concomitant presence of more that one trigger may be required to provoke an attack--for example, one study showed that chocolate alone rarely precipitated a migraine. The mechanistim of this association with migraine remains unclear; allergy seems to be an unlikely candidate, but some studies suggest that vasoactive substances in foods may be implicated. Foods do not seem to be associated with triggering tension headaches. On the other hand, it is likely that some migraines experienced by some people are provoked by food, probably in conjunction with another trigger, but there does not seem to be a common cause.

Recent antimilk propaganda from PETA (the People for the Ethical Treatment of Animals), targeting schoolchildren, has claimed that milk causes excess production of mucus and phlegm. This seems to have been part of folklore for some time, but there is no evidence for this association.¹¹ Another myth concerns the claimed link between food allergy and the development of obesity. We are often asked about this in our dealings with journalists, but so far as we know this is also wholly without foundation.

The British Nutrition Foundation is an independent registered charity, which raises funds from the food industry, the government, the EU Commission, and other sources.

As a result of concerns about the misleading nature of many media articles on food intolerance, in Spring 1999 the British Nutrition Foundation set up a task force, comprising UK based international experts in the field of food allergy and intolerance, to establish the scientific consensus and to provide sound and practical advice. The deliberations of the task force, in the form of a report, will be launched in November 2001 at a conference in London (see www.nutrition.org.uk for details). The report will inlcude a chapter tackling contemporary issues in a question and answer format. The foundation believes that interesting and entertaining newspaper and magazine articles can be written, without sacrificing scientific integrity, if journalists are disciplined in their use of nomenclature and conscientious enough to find an authoritative source and to take the opportunity to check copy before publication.

Further reading

British Nutrition Foundation Task Force. Adverse reactions to food. Buttriss J, ed. Oxford: Blackwell Science, 2001.

Judy Buttriss, science director, British Nutrition Foundation
Email: j.buttriss@nutrition.org.uk


studentBMJ 2001;09:399-442 November ISSN 0966-6494

1. Young E, Stoneham MD, Petruckevich A, Barton J, Rona R. A population study of food intolerance. Lancet 1994;343:1127-30.
2. Ellis HJ. In: J Buttriss, ed. Adverse reactions to food. Report of a BNF task force. Oxford: Blackwell Science, 2001.
3. Department of Health. Folic acid and the prevention of disease. Report on health and social subjects 50.
   London: Stationery Office, 2000.
4. Cant AJ. Food allergy and intolerance. In: McLaren DS et al, eds. Textbook of paediatric nutrition. 3rd ed.
   London: Churchill Livingstone, 1991:204-21.
5. Falth-Magnusson K, Kjellman NI. Allergy prevention by maternal elimination diet during late pregnancy--a five year follow up of a randomised study. J Allergy Clin Immunol 1992;89:709-13.
6. Kramer MS. Maternal antigen avoidance during pregnancy for preventing atopic disease in infants of women at high risk. Cochrane Database Syst Rev, 2000;(4):CD000133.
7. Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Peanut allergy. London: Department of Health, 1997.
8. King TS, Elia M, Hunter JO. Abnormal colonic fermentation in irritable bowel sydrome. Lancet 1998;352, 1187-9.
9. Collins SM, Barbara G, Vallance B. Stress, inflammation and the irritable bowel syndrome. Can J of Gastroent 1999; 13, 47­9A.
10. Food Standards Agency. Adverse reactions to food and food ingredients. London: Food Standards Agency,2000.
11. Pinnock CB, Arney WK. The milk-mucus belief: sensory analysis comparing cow's milk and a soy placebo. Appetite 1993;20: 61-70.

       

           

	EDUCATION Food intolerance: sifting the facts from the fantasies       Judy Buttriss (November 2001)
	Ginevra Read (October 31, 2001)       fourth year medical student, Royal Free and University College, London ginervraread@hotmail.com
	I was pleased to see the article on food intolerance in the November issue.1 It raised important questions about beliefs held by some people about the adverse effects of eating wheat and dairy products. I have several friends who believe that they have allergies to dairy and wheat, some of whom avoid these food types altogether, because of unfounded and irresponsible myths propagated by the popular press, some alternative health practitioners, and word of mouth. I find this worrying not just because of the need for a balanced diet and an adequate supply of nutrients, such as vitamins and minerals, but also because it is used to legitimise unhealthy eating habits. One friend of mine who works for a well known fashion magazine told me that “only the fat girls in the office” still ate wheat and dairy products as it was “so unhealthy and fattening.” There is a need for articles like this to be published in the popular press so that the public can make educated and informed decisions about what they eat and I hope that the findings of the British Nutrition Foundation will receive as much coverage as the latest fad diet.

	EDUCATION Food intolerance: sifting the facts from the fantasies       Judy Buttriss (November 2001)
	Tarek S Arab (January 01, 2002)       6th yr medical student, King Abdul Aziz University medical school, Jeddah Kingdom of Saudi Arabia captflashheart@yahoo.com
	Reading the article I was disappointed to say the least that the usual hostility to ideas that cannot be " proven" using science was used as an excuse to reject outright the idea of " food intolerance", with the reality that this " backward concept" has helped millions of people worldwide experience better health, and increased feelings of well being completely and conveniently ignored. The issue of food allergy and food intolerance were confused and presented as one, it seems in order to invalidate any opinion other than " medical" opinion which was sad, as it refused to acknowledge the fact that many thousands of people have experienced improved health once they restricted their diets to foods that did not cause any kind of deleterious response as defined by the exacerbation of certain chronic conditions e.g. fatigue, asthma, gout, acne. I believe that in any case, as the " customer is always right" the " patient is always right". It is very easy for someone who has no experience of a traditonal or alternative health craft to denigrate it; what makes it more worrying is that certain professionals who are in a position from which they can affect the thought processes of an entire generation, wish to prove the axiom that education, far from broadening the mind actually closes it off to new possibilities , based only on the fact that they are outside the traditional realm. Absence of proof is not proof of absence, and applies in this case. I am a chronic asthmatic and have heard that in the case of asthmatics, " intolerances" to wheat and dairy products are evident, both apparently being the cause of increased mucus production in the respiratory tract, and that avoidance of these foods would result in considerable cessation of symptoms of dyspnoea and productive cough. I was initially sceptical to say the least as none of this was ever mentioned in our medical " bibles" as surely what ever was not mentioned in the books was of no benefit? From my own experience of testing this idea out on myself, this " fallacy" of an idea actually has a basis in fact; the 3 times a day dyspnoeic episodes that I had been experiencing and had been refractory to bronchodilatory therapy vanished. In their place came a feeling of much decreased nasal congestion, easier breathing and a greater sense of wellbeing. My own experiences were subsequently mirrored by those of several other asthmatics of my acquaintance , all of whom are medical students. I am not the first asthmatic who reported relief of symptoms of their condition on reducing consumption of certain foods and I assure you I will not be the last. My symptom relief cannot be explained by medical science, so by this token according to the tone taken in the article, am I " lying", or perhaps in a state of " self delusion?" Absence of proof is not proof of absence, and in the arena where experience counts for more than scientific studies that can be formulated to prove a hypothesis whilst claiming to be completely impartial,i.e. the so called" subjective" measure of wellbeing, the patient's own comments on their state of wellbeing and health, I believe that my experience and that of MILLIONS of people who found an improvement in their sense of well being and health on removal of certain foods in their diets , speaks greater volumes and is more sigificant that an article written by someone who does nothing more than parrot the existing medical view towards nutritional therapy, confusing two terms " intolerance" and " allergy" and thus showing that in reality, they were more concerned with fulfilling an agenda than actually informing others. We in medicine it seems increasing wish to treat the disease, and forget completely about the person who has the disease. Nutrional therapy cannot be evaluated scientifically, for the reason that is it not scientific, yet this does not mean it cannot be used side by side with allopathic medicine in alleviating illness. Being able to prove somethin scientifically is not proof of its goodness or value; thalidomide was proven scientifically to ease morning sickness, and we all know what else it was proved to do. None of us can prove scientifically that murder is wrong, yet we all agree that it is. Why not keep an open mind on ideas like " food intolerance" as well? Or perhaps in our arrogance as " medical scientists" when the reality is that medicine is more of an art and less scientific than anyone cares to admit, we think that we, the able bodied, and healthy clinicians, know more about health than our patients, when all we are ever taught is how to treat DISEASE ,that if our patients report that something " unscientific" benefited them, but cannot be explained by us along the narrow principles we are all indoctrinated with after 5 years at medical school, that they are "imagining" things? Modern medicine has reached a cross roads; every year there are millions of cases of iatrogenic illness, and more and more people are turning to alternative forms of treatment, prominent among which is dietary therapy. Many of these people are mature, educated people who require convincing, and are not the type to suffer fools gladly. Many doctors are now incorporating nutritional therapy into their practise with considerable success, and some of the greatest champions of the idea of " food intolerance" are medically qualified doctors!. Your article conveniently chose to ignore this, as this fact alone undermines the article to a fatal degree. To anyone interested I would recommend the reading of the book: "Nutritional medicine" by Dr Stephen Davies and Dr. Alan Stewart.