What is Lactose?
Lactose is a disaccharide formed by two sugars: glucose and galactose. It is the principle carbohydrate contained in mammal milk. In human milk it has a presence of about 7%. A correct digestion of lactose depends on the presence in the intestine of the LACTASE enzyme that splits it into the two easily digestible carbohydrates: glucose and galactose. As well as in milk, lactose is present in all its derivative forms: dairy products, cheese, custard, cream, ice cream, etc.
LACTASE deficit and Lactose intolerance
Lactose intolerance, or more correctly, lactose mal-digestion, is a condition characterised by gastro-intestinal disorders that arise after ingestion of foods containing this sugar, generated by a weak production by the duodenum intestinal cells of the lactase enzyme and the breakdown of lactose into glucose and galactose that in this form can be absorbed. This is not, as sometimes referred to, an allergy: eventual milk allergies are actually supported by particular proteins contained in milk. Lactose intolerance is the more common form of mal-absorption of carbohydrates and affects people of all ages. The intolerance is manifested in many people, often unaware of the cause of their suffering, with a series of gastro-intestinal disorders that can often mislead the doctor, resulting in inappropriate prescription as a consequence of the lack of a precise lactose intolerance diagnosis.
Diagnosis and therapy
Diagnosis is possible through a breath test and duodenal biopsy and through specific blood tests. A form of “transitory” lactose intolerance exists, particularly frequent in paediatric age. In these cases, a primitive cause (for example infective gastroenteritis) can cause a temporary lactose deficit. For this reason it is good practice in paediatrics to avoid administering milk on the first day of gastroenteritis as being a lactase deficit the undigested lactose may worsen the diarrhoea. The therapy is dietary and requires a reduction or total exclusion of foods containing lactose in the diet.
H2 Breath Test
The H2 Breath Test is a technique with many applications, such as the study of ideal absorption capacity, oral-caecal transit and pancreatic function, which are actually little known. This test is frequently included in investigations carried out to diagnose intolerance to certain carbohydrates. In normal conditions after ingestion lactose splits from the intestinal lactase into glucose and galactose that are then absorbed into the small-bowel; if there is a shortage of lactase, the lactose reaches the colon unaltered where it gets fermented by the bacterial flora producing various gasses among which hydrogen and carbon dioxide which in part pass into the blood circulation and are eliminated through the air in the lungs. This is the principle on which the hydrogen Breath Test is based. With the H2 Breath Test the quantity of hydrogen breathed present in alveolar air is measured by this test.
Who can undertake the lactose breath test?
The test can be useful in those patients who report gastroenterological upsets such as flatulence, trapped wind, diarrhoea, abdominal distension and cramps following the ingestion of milk and its derivatives.
How does the lactose breath test work?
The test consists of a collection of breathed air samples, before and after ingestion of one specific sugar dissolved in water (lactose), into a plastic bag at regular intervals. The test lasts four hours.
Preparation of the patient for the H2 Breath Test
The test is carried out nil-by-mouth (empty stomach)
- For 30 days prior to the exam avoid use of laxatives and antibiotics
- For 15 days prior to the exam avoid use of probiotics (lactic ferments, yoghurt, milk and any other derivatives of animal origins). Almond milk, soya milk and rise milk can be consumed)
- Abstain from using non-essential medicines in the 12 hours before the exam. On the day of the exam the patient can continue to take “life-saving” medicines such as those for blood pressure and the heart, avoiding however Eutirox
- The doctor must be sure that the patient does not have significant diarrhoea at the moment of the exam.
The day before the exam the patient must diet exclusively on:
- From 9pm of the day previous to the exam the patient must be completely nil by mouth (but can drink water freely)
- From 7am of the day of the exam the patient MUST remain nil by mouth, not wash their teeth, not smoke, not carry out sports or physical exercise
- It is advised to rinse the mouth cavity with clorexidine 0,2% 30 minutes prior to the first withdrawal
- During the test, smoking, drinking, eating, chewing gum or sweets, carrying out tiring physical exercise are all forbidden
During the test, the patient must ingest a specific quantity of lactose and then breathe into a bag in the subsequent 3 hours thereby producing air samples. The breathed air is then measured for the quantity of hydrogen it contains. In the case of lactose mal-absorption, after the ingestion of lactose and in absence of the enzyme that it must metabolise (lactase) , processes of fermentation take place in the intestine and the production of hydrogen increases, which is absorbed into the circulation and eliminated through the lungs via breath. The increase, compared to baseline values, of the production of gas from the ingestion of lactose indicates that the subject is intolerant to lactose. The test is considered positive when a peak of hydrogen registered in the breathed air is superior to the baseline values registered on arrival in the laboratory. Otherwise, the test is considered negative. Finally, based on the scale of the peak, the lactose intolerance can be classified as light, severe or moderate.