Allyl Dimethyl Sulfonium: A Novel Urinary Biomarker of <i>Allium</i> Consumption

Allyl methyl sulfide (AMS) is an odorous and bioactive major metabolite produced following <i>Allium</i> food consumption and is regarded as the culprit behind the "garlic breath". Indoleethylamine <i>N</i>-methyltransferase (INMT) can methylate a variety of thioethers to their respective sulfonium ions in humans, aiding in their urinary excretion. We hypothesize that AMS may serve as a novel target for INMT and be metabolized to the allyl dimethyl sulfonium (ADMS) ion, which would constitute a previously undescribed pathway for metabolism of <i>Allium</i> food. ADMS was synthesized, and analytical methods were developed to explore its existence and characterize its levels in humans. ADMS was indeed consistently detected in all volunteers over 6 weeks without dietary intervention and found to strongly respond to controlled garlic supplementation. Striking interindividual variability in urinary ADMS was observed and found to mirror other products of INMT, which is attributable to genetic variation. ADMS is a novel metabolite in humans, and its remarkably variable production suggests variable response in body odors and health effects of <i>Allium</i> food and can be used to assess <i>Allium</i> consumption in the general human population in future epidemiological studies. More products of INMT that can serve as biomarkers of sulfur-rich food intake await discovery.