Bacteria in the colon (large intestine) play a part in digestions. The aerobic bacteria in colon help in digestion of carbohydrates and sugars. However, some of these carbohydrates and sugars are converted into hydrogen. Bacteria can also release some chemicals in the colon. Sometimes, colon secretes water due to these chemicals and lead to diarrhea. A part of the hydrogen produced in the colon is absorbed into the blood. This gas is exhaled in the breath. Hydrogen and other chemicals are produced when some carbohydrates and sugar reach the colon.
It is the job of the small intestine to digest and absorb sugar and carbohydrate. The small amount of carbohydrates and sugar reaching colon cause no problem. The problem occurs when sugar and carbohydrate reach colon in a larger amount. It results into more hydrogen and other chemicals in the colon. The hydrogen in breath is collected and measured in lactose hydrogen breath test.
Lactose is not the only sugar that is not digested properly. Fructose is a sugar found in corn syrup. Sorbitol is a sugar found in low-calorie sweetener. Sucrose, fructose and sorbitol are other sugars that are sometimes poorly digested. Abnormal digestion of sugars is not the only reason behind the digestion issues due to bacteria.
Bacteria are found in both small and large intestines. There is a smaller number of hydrogen producing of bacteria present in the small intestine. On the hand, there is a larger number of hydrogen producing bacteria found in the large intestine. Sometimes, the larger number of bacteria from the large intestine move into the small intestine. This leads to another health issue known as small intestinal bacterial overgrowth.
In this condition, the small intestine does not get a chance to digest and absorb sugar and carbohydrate as bacteria digest sugar and carbohydrates. So, a large of amount hydrogen is produced in the small intestine.
In some cases, the food rapidly passes through the small intestine. The food does not stay in there for proper digestion of sugar and carbohydrate. The undigested carbohydrates and sugars are then digested by bacteria in the large intestine. The bacteria then convert it into gas.
Both bacterial overgrowth and rapid passing of sugar through small intestine are diagnosed with Lactose Hydrogen Breath Test. When sugar passes through the small intestine quickly the bacteria in large intestine converts it into hydrogen soon after ingestion. So, you exhale hydrogen in breath soon after ingesting sugar.
During the Lactose Hydrogen Breath Test, Hydrogen is produced twice in the case of small intestinal bacterial overgrowth. The first time hydrogen is produced when the sugar is digested by the bacteria in the small intestine. Second time hydrogen is produced when the food enters the large intestine.