Description
Carbohydrate in the gut lumen can be fermented by bacteria in the small intestine forming hydrogen as one of the bye-products . Some of this hydrogen is absorbed into the blood stream and there is a direct relationship between the hydrogen concentration in expired breath and the amount of unabsorbed carbohydrate in the intestine.
In clinical situations in which there is poor digestion and or absorption of carbohydrates breath hydrogen concentrations increase 4-6 hours after eating. If a patient has bacterial overgrowth the increase in breath hydrogen is detected only 1-2 hours after eating.