Diagnosis of food intolerance

The most common means of diagnosis is a hydrogen breath test.

The patient drinks a certain amount of a sugar solution on an empty stomach. Afterwards the patient will be asked to blow several times, at certain intervals (normally every half hour), into a device that measures the hydrogen (H₂) levels from the air exhaled.

Since the sugar is not being properly digested there are bacteria in the intestines which produce hydrogen, short-chained fatty acids and CO₂. The hydrogen reaches the bloodstream via the large intestine and will consequently be exhaled through the lungs. By measuring the levels of hydrogen (which, by the way, does not itself cause any symptoms) it is possible to perform a diagnosis using this non-invasive breath test.

The illustration above shows three patients. Person 1 (green) does not have food intolerance to the tested substance. The slight rise of hydrogen levels in Person 1 is normal, because healthy people also produce small amounts of hydrogen. Person 2 (red) shows a significant rise in hydrogen levels and is therefore intolerant (when showing symptoms) or has a malabsorption (when not showing symptoms). Person 3 (purple) shows a rapid rise of H₂-level within 60 minutes. This person has an intolerance with backwash ileitis.

Apart from measuring the H₂ values, a record of the symptoms is an important part of the diagnosis. This is because not every person reacts the same way. Some people have bacteria which do not produce hydrogen or have bacteria which use up the hydrogen and produce methane in the process. According to the most recent findings, it is also necessary to measure the methane levels. If symptoms such as bloating, abdominal pain, diarrhoea etc. appear during the test, then this is also a strong indication of intolerance.

The doctor concerned should also measure the blood sugar levels (except fructose testing) during the testing period. If an intolerance is present then the tested sugar is not absorbed into the bloodstream, resulting in the blood sugar level remaining the same. If there is no existing intolerance, then the blood sugar level will rise because the sugar is being absorbed into the system.

Preparing for the test

Your doctor should provide you with detailed information ahead of the test in order to be able to obtain a diagnostically conclusive result.

This includes:

• your needing to observe a short fasting period (12 hours before, no eating, just drink water)
• not using any toothpaste
• not smoking on the day of the test
• you should not have had a colonoscopy or an enteroscopy or have taken any antibiotics in the last four weeks before the test is administered

Practical Tips:

On the day of your test, take the day off! If you are intolerant, then you will spend a substantial part of the day in the most private room of the house – the toilet – and suffer from severe symptoms, because you will have ingested a high dosage of the very substance you cannot tolerate on an empty stomach!

Where possible, your doctor should also determine other blood values via a blood analysis (folic acid, B12, serum analysis, lipase, zinc and iron)

Sources include:
Born Peter, World J Gastroenterol 2007 November 21;13(43): 5687-5691 "Carbohydrate malabsorption in patients with non-specific abdominal complaints"
M.Zechmann, "NMI-Portal"
M.Ledochowski, "H2 Atemteste", verlag ledochowski, 1. Auflage, 2008

Last Updated on Monday, 10 January 2011 12:43