What is the aromatic compound excreted in urine after eating asparagus?
The odour in the urine of asparagus eaters probably comes from a variety of methyl sulphides, sulphoxides and sulphones. The production of these substances from asparagusic acid is genetically determined, an autosomally dominant trait reportedly found in about 40 per cent of the population. The ability to smell the substances is also genetically determined and is present in about 10 per cent of people. Not everyone finds the odour offensive. Juvenal Urbino, in Gabriel Garcia Marquez's Love in the Time of Cholera, "enjoyed the immediate pleasure of smelling a secret garden in his urine that had been purified by lukewarm asparagus".
J K Aronson, Department of Clinical Pharmacology University of Oxford