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These disorders depend on the lack of digestion and / or absorption of particular nutrients taken from the diet; clear is the example of lactose intolerance, a widespread disorder in which the ingestion of milk and derivatives leads to episodes of flatulence, abdominal distension, diarrhea and more or less intense pains in the lower abdomen, often non-specific and not easy to classify diagnostic (because they are also common to diseases such as celiac disease, ulcerative colitis and irritable bowel syndrome).
To learn more: Lactose intolerance normally absorbable, such as lactose, sorbitol, fructose or glucose, or non-absorbable such as lactulose and xylose.
In these cases, the operating method of the breath test, conceptually simple, involves the assumption of a predetermined dose of a certain sugar (for example 20 grams of lactose) and the subsequent analysis of the gases exhaled by the patient after a certain period of time. In particular, the hydrogen peak in the exhaled air is sought, the presence of which is an indicator of intestinal fermentation of the unabsorbed sugar by the bacterial flora of the colon.
oral lactose is a simple, reliable and non-invasive test, useful for the diagnosis of lactose intolerance: this is why it is now considered the gold standard.Lactose intolerance
Lactose, a characteristic sugar of milk and dairy products, is a disaccharide composed of the union of the two monosaccharides: glucose and galactose. In order for lactose to be absorbed by the intestinal villi, this bond must necessarily be split, releasing the two monosaccharides that are then absorbed at the jejunal-ileal level (intermediate and final sections of the small intestine). The author of this event is the lactase enzyme, predisposed to digest lactose. Unfortunately, a good portion of the Italian population (about 30-40%) has very low amounts of lactase in their intestines; consequently the lactose is not digested and continues its intestinal transit without being absorbed.
How does it work
Once the unabsorbed lactose reaches the colon, the local microbial flora ferments it with the production of gas (hydrogen, methane, and carbon dioxide), giving rise to the typical phenomena of lactose intolerance (meteorism, flatulence, nausea and cramping pains ).
Part of these gases is reabsorbed by the mucous membrane of the colon, then transported by the venous blood to the pulmonary alveoli and eliminated by breathing; therefore, detecting the quantity of hydrogen in the air exhaled by the patient it is possible to diagnose lactose intolerance.
For example, if 20-25 grams of lactose are administered (15 in the case of pediatric patients), corresponding to 400-500 ml of milk, the breath test is considered positive when in the exhaled air, after 30-60-90-120- 150 and 180 minutes after ingestion, there is a hydrogen peak higher than the basal values, detected through an initial test upon arrival in the laboratory.
On the basis of the magnitude of this peak, lactose intolerance can be classified into mild, severe and moderate, a peak that is not recorded in the subject who digest lactose without problems.
The duration of the exam is about 3-4 hours.
poor, compromised by the use of antibiotics or by the abuse of laxatives and enemas; these subjects may in fact be falsely negative on the test (therefore appear healthy despite being actually lactose intolerant).
For this reason, in terms of optimal preparation for the breath test, it is important:
- stop taking antibiotics and pancreatic extracts in the 7-15 days preceding the examination;
- suspend lactic ferments, laxatives or antidiarrheals at least one week before the test;
- avoid, in the 24 hours preceding the examination, milk and dairy products of animal origin (allowed, for example, soy or rice milk), but also all food products that may contain lactose as an additive: milk sandwiches and baked goods, biscuits, sweet pizzas, pies, plum cakes, sweets, snacks, chocolate, nutella, ice creams, creams, puddings, various sauces and condiments, cold cuts and sausages with the exception of raw ham, coppa, culatello and bresaola. , the evening before the exam, eat only and exclusively rice, non-preserved meat, eggs and fish, season only with oil and salt, avoid butter and margarine, and drink only water (sparkling or non-sparkling).
- From 9.00 pm of the day before the examination the patient must observe a complete fast (he can freely drink still water).
- Also keep in mind that lactose is used as a base for more than 20% of prescription drugs and for about 6% of over-the-counter pharmaceuticals.
- Abstention from all possible sources of lactose in view of the breath test must be particularly careful and scrupulous in case of marked intolerance to sugar.
Do not smoke the day before the exam.
Fasting on the morning of the exam. - During the test, you should avoid eating and smoking. Only a small quantity of still non-carbonated water (half a glass) can be taken.
It is advisable to postpone the execution of the lactose breath test in the presence of severe diarrhea and acute intestinal diseases, such as salmonellosis and vital gastro-enteritis; the same is true in the case of recent (less than 30 days) undergoing diagnostic procedures such as colonoscopy or barium enema.
False positives are less frequent and linked to the presence of bacterial overgrowth in the small intestine.
If conducted in full compliance with these rules, the breath test allows you to diagnose lactose intolerance with certainty, directing the clinician and the patient towards correct food choices.
