What is Breath Hydrogen?
Hydrogen is not produced by human cells and arises exclusively from bacterial fermentation of carbohydrate. Following ingestion of a test substrate, hydrogen generated by fermenting bacteria diffuses across the intestinal mucosa into the portal circulation, is carried to the lungs, and is exhaled in measurable quantities. In a normally colonised gut, fermentation occurs predominantly in the colon, producing a late rise; earlier fermentation implies bacterial activity in the small bowel.