Diagnosing lactose intolerance

People can get an approximate picture of their own tolerance of lactose by drinking one or two glasses of milk after fasting and by observing what characteristic symptoms appear. A less dramatic way is to remove any product that contains lactose from one’s diet for a period of two weeks (see Treatment for further information on these) to establish whether the symptoms disappear. In most cases, even after only a few days a major improvement will be noticed. However, only a doctor can provide a definitive diagnosis. To achieve this, several tests may be used. These are described below.

The breath-hydrogen test
One of the tests is the breath-hydrogen test which measures the amount of hydrogen in the air expired by the patient before and after ingesting 10 grams of lactose in solution. The lactose that is not digested in the small intestine is metabolized through the action of bacteria and in the process produces a large amount of gas by fermentation. These bacteria are found in the large intestine which follows the small intestine. One of the gases produced is hydrogen. The hydrogen then gets absorbed into the blood stream and returns to the lungs from where it is exhaled together with the air. The more hydrogen is found in the expired air, the less effective is the digestion of lactose in the small intestine indicating a reduced capacity of the body to produce lactase, the enzyme that is needed for the digestion of lactose.

Lactose tolerance test
The lactose tolerance test involves the measurement of the level of glucose in the blood following the ingestion of a given quantity of lactose. At this point, it is useful to remind ourselves that the lactase breaks up the lactose into glucose and galactose, and the latter in turn transforms into glucose. The glucose then enters the blood stream with the effect that the blood sugar level of the patient increases. In case of less then perfect digestion of the lactose, the blood sugar level rises only moderately, or indeed not at all. (These last two tests are not recommended for very young children because such a large amount of lactose can induce a severe diarrhea and a consequent high risk of dehydration. Dehydration of course constitutes a much greater danger to small children than to adults.)

The genetic test GenoType LCT
This gene test which has only recently become available has obvious advantageous over the “breath-hydrogen test” and the “lactose tolerance test”. Indeed, the GenoType LCT test is a sure means for detecting primary lactose intolerance. There is in this case no danger of confusing it with secondary lactose intolerance. In addition, because the analysis is done from a blood sample, the patient does not have to ingest large quantities of lactose – which means there won’t be any uncomfortable symptoms to be put up with – nor does the patient have to remain under medical observation for a lengthy period. Clearly, because of these advantages this test is also particularly suitable for young children.