Gut Reaction

The public seems to have a hard time digesting the difference between food intolerance and the more serious food allergy. Dr Thomas Stuttaford reports

The confusion which surrounds the diagnosis of food allergies and intolerance is a reliable source of income for charlatans, and a guaranteed way of increasing the level of anxiety in many patients who are already riven by health worries. Unfortunately the overdiagnosis of food allergies, and a lack of understanding of the difference between food intolerance and a food allergy, has resulted in many cases of the latter being either ignored or belittled, sometimes with tragic results. An allergy to peanuts can be a potential death sentence, whereas an intolerance to lactose - and hence dairy products - may result in abdominal pain, an excess of wind, bloating and diarrhoea but within a few hours the patient will be as right as rain. Some people, usually small children or babies, may be allergic to cow's milk, whereas intolerance to dairy foods affects the population in many parts of the world from adolescence onwards.

A scientifically based survey in the United States showed that although 33 per cent of the population claimed to be allergic to some food or another only about one per cent are. The others are probably food intolerant. Nine out of 10 of those few people who have a genuine allergy are allergic to one in eight foods - cow's milk, eggs, wheat, peanuts, soya, fish, shellfish, or nuts other than peanuts.

Food intolerance, to deal with the lesser problem first, follows an abnormal reaction to some item of food. For instance people who are lactose intolerant and can't take milk or cheese without discomfort have less of the lactase enzyme in their small intestine than is usual. In these cases the milk - instead of being digested in the small gut - flows into the colon. Undigested milk in the colon sets up an adverse reaction which results in all those distressing symptoms caused by excessive gas formation, flatulence, and an overstimulated bowel. The patient isn't allergic to milk, they merely belong to the unfortunate section of humanity who have inadequate supplies of lactase. Food which for any other reason is poorly digested and passes in this undigested state too quickly down the gut may induce similar symptoms. Continental doctors, probably rightly, attribute many cases of food intolerance to inadequacies in the production of pancreatic enzymes. These cases are particularly intolerant of fat.

Other people are intolerant of certain foods because of some often long forgotten incident in their childhood. The taste, for instance, of cod liver oil is nauseous - if a child has been forced to swallow it when an infant for the rest of their life they may feel sick as soon as they smell it. They are intolerant of cod liver oil, certainly not allergic to it. One patient was told by a sibling that bananas harboured small poisonous spiders, who had hitched a lift from the Caribbean, and were just waiting to leap out once the banana skin had been peeled back. She always felt ill and sweaty when presented with a banana - she too wasn't allergic to bananas but had been made psychologically intolerant to them.

An allergy describes something which is quite different. This is not a question of a deficient digestive system, an abnormally sensitive sense of smell and taste, nor a psychological phobia. This is a real physical problem which can have far reaching results as the consequence of a physical reaction which produces a well recognised set of signs and symptoms. An allergy is the abnormal response of the immune system to an antigen, also known as an allergen. These people are hypersensitive (over sensitive) to the allergen, some particular protein in the foodstuff which overstimulates the immune response and produces an antibody of a type known as an IgE. When allergens in the food of a patient sensitive to them come into contact with any tissue bound IgE antibody in an already sensitised person - those who have previously eaten that particular foodstuff - the effect can be disastrous, even explosive. Histamine is produced, as is serotonin, and this can result in all the signs and symptoms of an allergic reaction of varying severity. If the patient is lucky there may be no more than runny eyes, runny nose, sneezing, wheezing and some inflammation. In other cases, and with other allergens, there may be an anaphylactic reaction and even anaphylactic shock. These patients may have urticaria - a widespread rash, like the rash caused by nettles - swelling of the face, mouth, lips, tongue, flushing, obstruction to the airways and irregular heart beat. In the worst cases shock may develop, the patient becomes very breathless and the heart may fail.

A report in the New Scientist suggested recently that some people became addicted to foods. In my days working in a clinic dealing with drug abuse we defined addiction very precisely, the difference between that and psychological dependence, which is the explanation usually given for obsessive eating. Psychological dependence wasn't included within the definition of addiction but it sometimes now is.

Physical addiction is a state in which the person has a compulsive need for the drug even if they are aware that the drug is causing them harm. Characteristically ever increasing doses of the drug are needed to achieve the sense of relief. The suggestion of Diane Martindale in the New Scientist, who has garnered some well founded evidence that a high fat diet may affect the hormonal balance of the appetite control system in the brain, is that people may develop a dependence on food, which almost reaches the definition necessary for the term addiction.

Before addiction could be diagnosed there had to evidence that leaving off the drug produced physical signs and symptoms - withdrawal symptoms: the cold turkey of a thousand novels written in the 60s and 70s. The other symptoms of addiction are less specific - a collapse in the social/work life resulting in unemployment or social isolation or a change in the pattern of friendship. I have never met anyone who is so captivated and dependent on beefburgers and chips or other convenience foods that they would suffer measurable physical side effects if the refrigerator key was lost.

Psychological dependence is rather different. These people become very emotionally dependent on their food, and are obsessed by food. They plan the next meal. Even when they are not buying food, cooking it, smelling it, and eventually eating it, they are planning menus, remembering past meals and day dreaming about future ones.

Food intolerance - a poor digestion with wind, abdominal pain and all the other tiresome symptoms - can obviously be helped by avoiding some foods but all those who have digestive problems are well advised to eat slowly. They should, as Mr Gladstone suggested, chew the food very finely so that saliva can start the digestive process. As well as avoiding foods known to the patient to bring on intolerance they may also be well advised to cut back on such things as beans and cabbages, lettuce, onions, very rich fatty foods, highly spiced foods, strong coffee and alcohol - the darker the alcohol the more it is likely to upset a delicate digestion. Above all they need to eat when totally relaxed - the digestion will pick up tension when the mind hasn't noticed it. Everyone knows that a sexually exciting partner may destroy appetite and digestion, but even the presence of a business colleague or adversary may have a similar effect. Food allergies are important medicine. Professional advice is essential, and anyone who has ever shown signs of an anaphylactoid reaction (swollen lips etc.) should always carry an Epipen with them so that adrenaline is immediately available.