Sulfate-reducing bacteria (SRB) in the gut produce Hydrogen Sulfide (H2S) internally and externally in humans. H2S plays an essential role in the control of vascular homeostasis, and ongoing studies have shown that extreme levels of SRB in the gut may cause small intestinal bacterial overgrowth (SIBO). Gastrointestinal disorders such as irritable bowel syndrome, ulcerative colitis, and Crohn’s disease have also been linked to changes in H2S levels. Therefore, H2S may be an important breath biomarker of intestinal health and dysbiosis, but there is currently a lack of data to understand the normal ranges of H2S in humans, which limits its clinical use by practitioners.
Determining Normal Hydrogen Sulfide Levels with CDI Breath Tests
A recent study by Owlstone Medical investigated the normal levels of H2S in human subjects. Hydrogen and methane breath tests from Functional Gut Diagnostics, Commonwealth Diagnostics International (CDI)’s exclusive distributor of hydrogen and methane breath tests (HMBTs) in the United Kingdom, were utilized in the study. The study recruited participants aged 18-60 who were neither pregnant nor breastfeeding nor had any significant medical condition. It was also ensured that the participants were not taking regular prescription medications, laxatives, or promotility agents and had not performed any form of bowel cleansing about one week before the study. Patients also maintained a low fermentable diet about 24 hours before the application of the breath test and were asked to avoid food, drinks, water, exercising, smoking, and sleeping during the test.
A baseline breath sample was collected before participants ingested 10g of lactulose dissolved in water. More breath samples were taken at 15-minute intervals for 180 mins to analyze hydrogen and methane levels. Similarly, samples were taken for hydrogen sulfide analysis at 45, 90, and 180mins after lactulose ingestion. Hydrogen and methane samples were analyzed using gas chromatography and H2S via selected ion flow tube mass spectrometry (SIFT-MS). -MS.
Participants in the study collected samples for hydrogen and methane analysis by exhaling into a breath test tube for just 3-5 seconds. The participants also provided samples for hydrogen sulfide analysis by exhaling into 500ml polyvinylidene fluoride bags.
Results
Hydrogen and methane levels increased as the study progressed while hydrogen sulfide reduced. Imperatively, hydrogen sulfide decreased as lactulose was fermented. The result of the study agrees with the findings of Birg et al. in 2019. The levels of H2S were constantly below 50ppb. This suggests a physiological range that can be used in future clinical studies.
Currently, no diagnostic technology on the market can test for H2S at levels of parts per billion (PPB) accomplished in this study.
Mean hydrogen (H2), methane (CH4), and hydrogen sulfide (H2S) production in parts per million (ppm) for hydrogen and methane, and parts per billion (ppb) for hydrogen sulfide over a 3hr lactulose breath test.
The report, Hydrogen Sulphide and its Role in Gastrointestinal Disease, was originally published by Owlstone Medical on July 11, 2022.
