Differentiation of mouth versus gut as site of origin of odoriferous breath gases after garlic ingestion

Utilizing the sulfur-containing gases of garlic as probes, we investigated the gut versus mouth origin of odoriferous breath gases. Five individuals i ngested 6 g of garlic, and sulfur gases in mouth, alveolar air, and urine s amples were measured. The mouth normally contained low concentrations of hy drogen sulfide, methanethiol, and dimethyl sulfide. Immediately after garli c ingestion, transient high concentrations of methanethiol and allyl mercap tan and lesser concentrations of allyl methyl sulfide (AMS), allyl methyl d isulfide, and allyl disulfide were observed. With the exception of AMS, all gases were present in far greater concentrations in mouth than alveolar ai r, indicating an oral origin. Only AMS was of gut origin as evidenced by si milar partial pressures in mouth, alveolar air, and urine. After 3 h, AMS w as the predominant breath sulfur gas. The unique derivation of AMS from the gut is attributable to the lack of gut and liver metabolism of this gas ve rsus the rapid metabolism of the other gases. Breath odor after garlic inge stion initially originates from the mouth and subsequently from the gut.