Lactose intolerance is a condition where the body has difficulty digesting lactose, the sugar found in milk and dairy products. Diagnosing lactose intolerance involves a combination of understanding symptoms, medical history, and conducting specific tests that measure how well the body processes lactose.
One of the most common and reliable methods to diagnose lactose intolerance is the **hydrogen breath test**. This test works because when lactose is not properly digested in the small intestine, it passes into the colon where bacteria ferment it, producing hydrogen gas. This hydrogen is absorbed into the bloodstream and eventually exhaled through the lungs. By measuring the amount of hydrogen in the breath after consuming lactose, doctors can determine if lactose digestion is impaired.
The hydrogen breath test procedure typically starts with an **overnight fast** to ensure that the digestive system is clear of other food substances. Then, the patient drinks a liquid containing a measured amount of lactose, usually between 25 to 50 grams dissolved in water. After ingestion, breath samples are collected at regular intervals, often every 15 to 30 minutes, over a period of two to three hours. If the hydrogen levels in the breath rise significantly above the baseline, it indicates that lactose is not being properly digested and is fermenting in the colon, confirming lactose intolerance.
Another diagnostic approach is the **lactose tolerance test**, which measures the body’s blood glucose response after consuming lactose. Since lactose breaks down into glucose and galactose, a normal response would be a rise in blood glucose levels. In this test, after fasting overnight, the patient drinks a lactose solution, and blood samples are taken at intervals to measure glucose levels. A smaller than expected increase in blood glucose suggests poor lactose digestion, indicating intolerance.
In some cases, doctors may also use an **elimination diet** to help diagnose lactose intolerance. This involves removing all lactose-containing foods from the diet for a few weeks and monitoring symptoms. If symptoms improve during this period and return when lactose is reintroduced, it supports the diagnosis of lactose intolerance. This method is often used alongside other tests to confirm the diagnosis.
For infants and young children, diagnosis can be more challenging because symptoms may overlap with other digestive issues. Pediatricians often start by observing symptoms such as diarrhea, bloating, and fussiness after feeding. If lactose intolerance is suspected, the hydrogen breath test can be adapted for children, or doctors may rely on symptom monitoring and dietary changes.
In rare cases, if the diagnosis remains unclear, doctors might perform a **small intestine biopsy** to directly assess lactase enzyme activity, but this is invasive and usually reserved for complicated cases.
It is important to distinguish lactose intolerance from milk allergy, which involves the immune system and requires different testing methods such as skin prick tests or blood tests for specific antibodies. Lactose intolerance is a digestive issue caused by enzyme deficiency, not an allergic reaction.
Overall, diagnosing lactose intolerance involves a careful combination of symptom assessment, dietary history, and specific tests like the hydrogen breath test and lactose tolerance test. These methods help ensure an accurate diagnosis so that appropriate dietary adjustments can be made to manage symptoms effectively.
