The sorbitol H2 breath test (synonym: sorbitol tolerance test) is used to diagnose sorbitol intolerance (sorbitol intolerance; sorbitol malabsorption) and then to reduce symptoms with a diet. In the case of sorbitol intolerance, the utilization of sorbitol in the small intestine is completely or partially suspended. Sorbitol (synonyms: sorbitol, glucitol) is a sugar substitute derived from glucose and has about 60% of its sweetening power. It is converted to fructose in the liver and can be utilized independently of insulin (insulin is a hormone whose action mediates the absorption of sugar into cells). This property makes sorbitol a suitable sweetener for diabetics. In addition to diet foods, sorbitol is contained in many chewing gums and lozenges because it is non-cariogenic. It occurs naturally in various types of fruit, including apples, pears, hawthorn fruit, cherries, plums and apricots. Sorbitol tolerance results in symptoms such as:
- Diarrhea (diarrhea)
- Meteorism (flatulence)
- Abdominal pain (abdominal pain)
Sorbitol tolerance is often accompanied by fructose intolerance or other carbohydrate intolerances and is not curable. However, adequate diet can achieve freedom from symptoms.
Confounding factors
In order for the test to be performed without error, some requirements must be met:
- The patient should refrain from nicotine consumption as far as possible.
- The patient should remain fasting for twelve hours before the examination.
- No antibiotic administration one week before the examination (this could destroy the normal intestinal flora).
- No intestinal cleansing measures (one week before the examination).
- No contrast studies of the intestine (one week before the examination).
- No legumes (up to 3 days before the examination).
- No proton pump inhibitors – medications used to decrease stomach acid (up to 3 days prior to examination).
- No acid secretion inhibitors or antacids (12 hours before the examination).
Indications (areas of application)
- Suspected sorbitol intolerance (sorbitol malabsorption).
The procedure
The sorbitol tolerance test is a so-called H2 breath test (sorbitol H2 breath test; H2 exhalation breath test; hydrogen breath test; hydrogen exhalation test). It is based on the following principle: carbohydrates are broken down by bacteria in the large intestine, resulting in the production of molecular hydrogen (H2), which enters the lungs via the bloodstream and is exhaled. Hydrogen production by bacteria increases when carbohydrate degradation mechanisms, such as sorbitol, are inefficient. The concentration of hydrogen in the breath correlates with the amount of unmetabolized sorbitol and can be measured. The test procedure is as follows: First, the hydrogen concentration in the patient’s breath is determined (basal value). Now the patient ingests 5 g of sorbitol in either 100 ml of water or unsweetened peppermint tea. The hydrogen concentration is then measured again at 20-minute intervals for approximately three hours and recorded. Complaints related to sorbitol intake are also recorded. If sorbitol intolerance is present, the hydrogen concentration in the breath rises above a defined value and symptoms occur. During the H2 breath test for sorbitol, a pust interval of approximately 20 minutes is recommended. Hydrogen concentration readings are expressed in parts per million (ppm). Duration of the test: 3 hours
Interpretation
Basal value is the initial value measured before drinking the test solution. Subsequent readings are taken every 20 minutes after ingestion of the test substance. If one of the values – or two consecutive values – rises above 20 ppm above the basal value, then the test is considered positive. False-positive results are possible and are usually caused by:
- A short bowel – the physiological absorption area is reduced and too little sorbitol is absorbed without an intolerance being present.
- A bacterial miscolonization (dysbiosis; disturbance of the intestinal flora) – only with an intact intestinal flora, the test results can be evaluated correctly
- A short small intestine passage time – here is also the physiological absorption reduced and more sorbitol is metabolized by the bacteria.