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Chapter 36 : Spotlight on Acetaldehyde
Mikko Salaspuro, of the University of Helsinki in Finland, and his colleagues discovered that normal human colonic contents, especially their aerobic bacteria, generated significant quantities of acetaldehyde when incubated aerobically or microaerobically with ethanol in vitro. Writing in the Scandinavian Journal of Gastroenterology, they suggested that this bacterial adaptation might be an essential feature of what they called the bacteriocolonic pathway to form acetaldehyde from exogenous (or endogenous) alcohol. Another type of evidence comes from studies on Oriental flushers. These are individuals with genetically deficient aldehyde dehydrogenase (ALDH2) whose faces redden after they consume alcohol; the partially inactive enzyme cannot deal quickly enough with acetaldehyde produced by alcohol dehydrogenase (ADH). As a means of preventing the adverse consequences of this accumulation, Salaspuro and his colleagues experimented with the nonessential amino acid L-cysteine. This reacts covalently with acetaldehyde (to form 2-methylthiazolidine-4-carboxylic acid). In principle, therefore, it could be used in slow-release tablets to forestall carcinogenicity. A further strand of evidence comes from the comparison of saliva from different individuals who varied in their capacities to produce acetaldehyde. The observation of increased yeast colonization in patients with poor dental hygiene might be of special interest since several Candida strains have been shown to occur more frequently and in higher densities in risk groups of oral cancer.