What is Hydrogen Breath Testing?
Hydrogen breath testing is used to diagnose three primary conditions. First, hydrogen breath testing detects sugars like lactose that are not properly digested and metabolized. Secondly, hydrogen breath testing detects sugars like fructose that are not absorbed in sufficient levels. Thirdly, hydrogen breath testing is used to diagnose bacterial overgrowth of the small bowel.
Hydrogen breath testing is the most common method to diagnose small intestinal bacterial overgrowth (SIBO) in clinical practice due to its low risk, lower costs than intestinal cultures of small bowel aspirates, and ease of use. SIBO hydrogen breath testing uses the orally ingested carbohydrate lactulose as a substrate.
Hydrogen and methane gas are only produced in the body from intestinal bacteria. Bacteria ferment sugars such as lactulose to hydrogen and/or methane gas. Hydrogen and methane are absorbed by the intestinal mucosa, enter the vasculature, and get transported to the lungs. A change in the level of hydrogen and/or methane gas above 20 parts per million within 60 minutes is diagnostic for SIBO. The majority, but not all malabsorbers produce hydrogen gas. Approximately 15% of patients are methane producers rather than hydrogen producers. These patients will only be properly diagnosed by measuring methane levels. As a result, each breath specimen is measured by Metabolic Solutions for hydrogen and methane.
What causes Bacterial Overgrowth?
Normally the proximal small intestine contains no or low levels of colonic-type bacteria. Small intestinal bacterial overgrowth is the presence of anaerobic organisms in an atypical location of the small bowel. SIBO is defined as the presence of >105 colony forming units per milliliter (cfu/ml) in the proximal small intestine. It has been suggested that even 103 cfu/ml can induce symptoms of bacterial overgrowth if the bacterial species are colonic in orgin.
Two major factors are responsible for controlling the number of bacteria in the small bowel. Normal small bowel motility is the first defense against attachment of bacterial organisms to intestinal walls. Gastric acid is the second defense by destroying invading ingested organisms. Both of these mechanisms are compromised during the natural aging process and with the presence of anatomical changes, functional pH or dysmotility syndromes, or miscellaneous diseases that introduce motility derangements.