The hydrogen breath test is a non-invasive diagnostic tool that helps identify gastrointestinal conditions by measuring gas levels in a person’s breath. This test provides insights into how the body processes specific sugars and the activity of bacteria within the gut.
How the Test Works
The hydrogen breath test relies on the fact that humans do not naturally produce hydrogen gas. Specific bacteria residing in the gut generate hydrogen when they ferment undigested carbohydrates. If not properly absorbed in the small intestine, these carbohydrates reach the large intestine where bacteria break them down.
The hydrogen gas produced is absorbed into the bloodstream, travels to the lungs, and is exhaled. The test measures hydrogen (and sometimes methane) in breath samples collected at intervals after consuming a sugar solution. Elevated levels indicate undigested sugars are undergoing fermentation by gut bacteria.
Conditions Identified
A hydrogen breath test diagnoses conditions related to carbohydrate malabsorption and bacterial imbalances. The specific sugar administered helps pinpoint the issue.
Lactose Intolerance
Lactose intolerance, an inability to properly digest lactose, is a common condition identified. When individuals with lactose intolerance consume lactose, insufficient lactase enzyme prevents its breakdown in the small intestine. The undigested lactose then ferments in the colon. A rise of 20 parts per million (ppm) or more in breath hydrogen over baseline after lactose ingestion typically indicates malabsorption.
Fructose Malabsorption
Fructose malabsorption, characterized by difficulty absorbing fructose, is also diagnosed. If fructose is not absorbed in the small intestine, it reaches the large bowel where gut flora ferment it. A breath hydrogen increase of 20 ppm above baseline after fructose intake indicates a positive result.
Small Intestinal Bacterial Overgrowth (SIBO)
Small Intestinal Bacterial Overgrowth (SIBO) is diagnosed by excessive bacteria in the small intestine. For SIBO testing, lactulose or glucose solutions are used. A rapid rise in hydrogen (and/or methane) within the first 60-90 minutes after consuming the sugar suggests bacterial overgrowth, as fermentation occurs earlier than expected. A rise in hydrogen by 20 ppm above baseline within 90 minutes is often considered positive.
Other carbohydrate malabsorptions, such as sorbitol malabsorption, can also be detected. These tests help identify if various dietary sugars are contributing to gastrointestinal symptoms like bloating, abdominal pain, and altered bowel habits.
Preparing for the Test
Accurate hydrogen breath test results depend significantly on proper preparation. Dietary restrictions are crucial for a day or two before the test, typically involving a low-fiber and low-carbohydrate diet. This preparation minimizes bacterial activity in the gut, ensuring a low baseline hydrogen reading.
Foods to avoid often include:
Grains
Fruits
Vegetables
Dairy products (except eggs)
Items containing high-fructose corn syrup or artificial sweeteners
Recommended foods often include:
Plain white rice
Baked or broiled chicken, fish, or turkey with salt and pepper
Eggs
Clear chicken or beef broth
Certain medications must be avoided before the test. Antibiotics should be stopped at least four weeks prior, as they alter gut bacteria. Probiotics, laxatives, fiber supplements, and antacids should typically be discontinued one week before the test. A fasting period of 8-12 hours, meaning no food or drink (except water), is also required immediately before the test. Additionally, individuals should avoid smoking, vigorous exercise, and using certain oral hygiene products like mouthwash for several hours before the test to prevent false readings.
Interpreting Results and Next Steps
Interpreting hydrogen breath test results involves analyzing hydrogen and sometimes methane levels in breath samples collected over time. A healthcare professional evaluates these measurements, looking for a significant increase above baseline after specific sugar ingestion. Normal hydrogen values are typically less than 16 ppm.
A positive test result indicates the administered sugar was not fully absorbed and fermented by bacteria. Results are considered alongside a patient’s symptoms and other clinical findings for a comprehensive diagnosis. Based on the diagnosis, a doctor will recommend management strategies, which may include dietary adjustments, medication, or other interventions.