Unlike food allergies, there is little medical consensus when it comes to food intolerance. Clare Rudebeck underwent a series of tests in search of some answers

Over the past three weeks, I have taken four separate tests for food intolerance. There was no agreement between the results, except that two tests identified a sensitivity to cow's milk. The other two told me cow's milk was fine. The cost of the tests ranged from £45 to £260. The total number of foods I was told I had a significant intolerance to was 15.

Over the past three weeks, I have taken four separate tests for food intolerance. There was no agreement between the results, except that two tests identified a sensitivity to cow's milk. The other two told me cow's milk was fine. The cost of the tests ranged from £45 to £260. The total number of foods I was told I had a significant intolerance to was 15.

I have frequent headaches caused by excess catarrh. The head of Allergy UK, Muriel Simmons, told me that it was unlikely this was caused by food intolerance. Two of the testers (Ian Preston, on behalf of Health Screening UK, and John Graham, the chief executive of YorkTest) told me the opposite. I am exactly the kind of person who gets tested for food intolerance, having a chronic minor complaint and an open mind about alternative medicine. On the basis of this survey of the available tests, it is clear that the opportunities for wasting money and needlessly excluding foods are many. So is there a reliable test? Is there good advice somewhere?

The problem is that food intolerance is medically still an "iffy subject", as Dr Apelles Econs, the director of three allergy clinics (two private, one NHS) and a former GP, puts it. "There is currently no reliable test for food intolerance," he says. "There has been plenty of research, but so far all the tests fall short of the standards of accuracy that medical tests are expected to meet." Of the four I tried, only the YorkTest has successfully completed a clinical trial, although this is yet to be published.

There is no consensus about how many people suffer from food intolerance. The British Nutrition Foundation estimates that one to two per cent of adults and five to eight per cent of children are affected. Dr Econs estimates 40 per cent. Neither is it fully understood what is happening within the body, when a problem food is eaten.

By contrast, food allergy is well documented. It involves an immediate, often life-threatening, reaction by the immune system when a food is eaten.

Food intolerance is a separate condition. It is rarely severe and causes symptoms such as migraines, bloating, nausea, diarrhoea and chronic fatigue. It involves several different mechanisms within the body, some to do with the immune system, some not. "In the midst of this sea of variations, every Tom, Dick and Harry can claim some kind of diagnostic accuracy," says Dr Econs.

The only reliable way to find out whether you are intolerant to a food is to exclude it from your diet for four to six weeks and then reintroduce it. However, as the body may react up to 48 hours after the offending food is eaten, it is very difficult to work out which food to exclude and the process can take months or years.

The tests are designed to speed up this process. Muriel Simmons, the chief executive of the charity Allergy UK, says that she was initially sceptical about all the tests on the market. However, after overwhelming anecdotal evidence that the YorkTest was helpful, she decided to commission independent research and now recommends it.

She remains sceptical about the three other tests I tried. Dr Econs is not convinced by any of them. Neither is the British Nutrition Foundation. Until a reliable test is found, all warn that embarking on a drastic exclusion diet, based on test results, could be extremely damaging to your health. "I spoke to one woman who had been told to cut out 116 foods," says Muriel Simmons. "All she was left to eat was rice pudding. She was feeling very shaky. Well, surprise, surprise."

THE NUTRIMARK PROGRAMME

Availability

The nutriMARK programme, uses a Vega machine. Run by Health Screening UK Ltd (HSL), it is available at all Holland and Barrett stores and from many other independent venues.

How does it work?

The Vega machine passes a very small electric current through the body. I held a negative electrode in my right hand while my tester, Ian Preston, held a positive electrode to an acupuncture point on the tip of my middle left-hand finger, making a circuit. Different foods, in homeopathic quantities, were then placed in the machine. If the current then dropped, it was said to show a sensitivity.

How reliable?

No randomised controlled trials on detecting food intolerance with the Vega machine. Following recent criticism, Health Screening UK no longer relies exclusively on the Vega machine. Patients now also complete a detailed questionnaire about their diet and symptoms, which is analysed against a database of details about HSL's previous patients.

The experience

It was almost painless (giving me a small blister on my finger tip) and the results were available immediately. Ian Preston was brimming with advice, recommending I buy two books (on fats and yeast intolerance), two food supplements, an ioniser and that I take up Shiatsu massage and Alexander Technique. He said my headaches were "a common complaint" indicating food intolerance.

The results

Intolerance to wheat and cow's milk, which I was recommended to cut out of my diet for four weeks. Possible intolerances to corn, rice, egg, potato, peas, kiwi fruit, apple, coffee and yeast, which I was told to consider cutting out afterwards.

The cost

£45

THE NUTRON TEST

Availability

The NuTron Test is manufactured by Aeon Biotech Ltd. NuTron sends you to a nearby clinic, where a sample of your blood is taken and sent to its laboratories for analysis.

How does it work?

The blood sample is mixed with over 90 foods which have been reduced to "pure food solutions". After a period of incubation, the mixture is tested for neutrophil activation. Neutrophils are a type of white blood cell and, although the precise mechanism that causes food intolerance in the body is not fully understood, it has been shown that neutrophils do become activated in the presence of offending foods.

How reliable?

Clinical trials on this test have not yet been completed.

The experience

The NuTron programme is a package including the test and a managed diet that normally lasts 12 weeks. This is closely monitored by NuTron advisers. Before starting the programme, patients are warned that the diet will involve eating only those foods that the test has said they are not intolerant to. Amongst much else, this means no processed food, chocolate and alcohol for six weeks.

Foods are slowly reintroduced. Patients are also provided with extensive help on following the diet including recipes and information on useful brands. I only undertook the initial blood test, not the full programme.

The results

Intolerance to cheese, pork, oats, lettuce, buckwheat, beetroot, malt, haddock, turkey and egg white.

The cost

£235 for the full programme.

YORKTEST

Availability

This test involves an at-home blood test. It can be done by post and also through Lloyds Pharmacy outlets.

How does it work?

There are two tests. The first tells you if you have a food intolerance or not. The second test identifies specific foods to which you may be sensitive. It is known that some food intolerances are, in fact, delayed food allergies and therefore involve the immune system.

In this case, if you are intolerant to a food, your immune system produces an IgG antibody against that food. This test measures the amount of IgG antibodies in your blood.

How reliable?

In a recent double blind randomised controlled clinical trial at the University Hospital of South Manchester, 150 patients suffering from Irritable Bowel Syndrome took the YorkTest and were placed on either a diet based on their test results or a dummy diet. Those who followed the true diet showed "significant improvements" compared to those who followed the sham diet.

The experience

You receive a green plastic case in the post containing a swab, lancet, absorbent wand with container and a plaster. You swab your finger, prick it with the lancet and then "milk" your finger for blood until the absorbent wand is saturated.

The results

Intolerance to cow's milk and kidney beans. Lesser sensitivities to molluscs (including mussels, oysters and scallops), peanuts and yeast.

The cost

£19.99 for the first "yes/no" test. The second test costs £135, which tests for 42 foods, or £260, which tests for 113.

APPLIED KINESIOLOGY

Availability

At many alternative health clinics. This involves a non-invasive "manual muscle test". I went to The Hale Clinic in London.

How does it work?

Lying down on a couch, I was told to hold my left arm out. The practitioner, Dr Freya Bennett, held that arm firmly and asked me to push against her grip. Different foods, in homeopathic quantities, were placed at the bottom of my neck under a magnet. If the resistance of my arm muscle weakened, it was said to show a sensitivity. The test evaluates the nervous system, which controls the muscle. The idea is that if the body is put under stress, the nervous system will react.

How reliable?

No favourable randomised controlled trials on its accuracy detecting food intolerance.

The experience

Very relaxing. Dr Bennett is also a chiropractor and adopts a holistic approach to healing. She looks into your physical, emotional and chemical (including nutritional) well-being. During the course of the 45-minute consultation, she readjusted my spine and gave me a homeopathic remedy, as well as testing me for food intolerance.

The results

She said there was "a lot more to" my headaches than food intolerance and that my spine was also in trouble. However, she did detect intolerances to yeast and foods containing mould and fungus, suggesting I cut them out of my diet for four weeks.

The cost

£70 for the first session.

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