MALODOROUS BREATH (halitosis) is a common problem that has received extensive study (2-5, 10-12, 17-19). Virtually all of these studies have worked on the assumption that the malodorous compounds originate in the mouth (2-5, 10, 11, 17-19). However, there is abundant evidence that gases produced by the microflora of the gut, such as hydrogen and methane, are efficiently absorbed into the portal blood flow and then excreted in expired air (7). The extent to which odoriferous breath gases are derived from the mouth versus the gut has not been rigorously investigated. This differentiation is of importance because cleansing of the oral cavity would not be expected to appreciably reduce the breath concentration of gases derived from the gut.
Many people who feel that halitosis is their problem in our community are unsure if it's oral based or metabolic. Traditionally, metabolic halitosis has not been considered. Recently, because of trimethylaminuria, the few papers on that subject include the notion of trimethylaminuria halitosis.
In this paper, from 1999, they consider it the first looking into the concept of metabolic halitosis by provoking it with the consumption of garlic, which is commonly known to cause smells. For anyone who hasn't thought of the principle of metabolic odors before, another obvious example would be drinkers having alcohol breath and perhaps hours later having alcohol body odor too. This is basically consumption of so much alcohol that it is circulating freely in the blood. Another example would be those who get 'curry body odor' after eating a curry.
The results of this study demonstrate that halitosis may be of oral and/or gut origin. A rational approach to the treatment of this common problem presumably should begin with the identification of the malodorous gas and its site of origin. The simple techniques utilized in the present study make it possible to differentiate between a mouth versus gut origin. In the paper, they investigate where the garlic smells are coming from. They test the mouth breath, and the alveolar breath (breath from the lungs), and urine. Mostly, the compounds that turn up in their results are detected from the mouth breath largely, apart from allylmethyldisulfide (AMS), which turns up later in the urine. Through work they have done on rats, they have discovered that this isn't easily metabolized by rats or humans. They conclude that the other odorous compounds found were quickly metabolized when absorbed, and so didn't show in alveolar breath or urine in significant size. They used 'normal healthy' volunteers for testing. It may have been very different if they used metabolic body odor patients.
Currently, any expert interested in trimethylaminuria will likely only test for TMAU. It would be interesting to see how someone with a weakened FMO system coped with these Volatile Organic Compounds (VOCs) found in the garlic test, since most of them are likely FMO substrates. It seems ironic that those who are burdened with metabolic body odor are only offered the TMAU test whereas in the other tests done on pubmed they seem to test for all VOCs to see what turns up. Perhaps someday the metabolic body odor and halitosis test will be a blank check of VOCs, rather than just one compound.