"This is of no practical importance," the urologist tells me. "It wasn't part of my training. It's something we contemplated over pizza and beer." When I admit that I have actually timed the arrival of the distinctive odor in my pee after eating asparagus (about 15 minutes), the good doctor suggests, facetiously, that my groundbreaking research might lead to a tenure-track position at a fine university.
In 1891 a scientist named "Nencki" had so very little to do that he convinced four guys to eat seven kilograms of asparagus (that's about three and a half pounds each). He collected the pertinent pee, worked some medieval magic on it, and concluded that the smell was due to a metabolite called methanethiol.
So there you go. Nencki claimed that as your body metabolizes asparagus, it produces this smelly chemical, which your discriminating kidneys see fit to dump into the bladder.
In 1975 a chemist from California claimed in Science that gas chromatography had fingered a different culprit: S-Methyl Thioesters, to be precise. No methanethiol.
I'm voting for methanethiol, partly because the guy who did the gas chromatography left no forwarding address, and partly because the methanethiol entry in my aging Merck Index of chemicals is so interesting.
Methanethiol is composed mostly of sulfur with a splash of hydrogen, plus some carbon, a brew famous for its effect in rotten eggs, cabbages and paper mills. Convincing, no? Merck also notes the asparagus connection and, most intriguing, warns that methanethiol may be a narcotic in high concentrations.
Even if you do but lack the smell, you're still OK. In fact the fabulously funny book, The ReSearch Guide to Body Fluids (by Paul Spinrad, Juno Books, N.Y., 1994), says just 22 percent of survey respondents experience asparagus pee.
If you've been deprived of this gift, don't give up hope. To increase the concentration of methanethiol molecules available to your snoot, you could either intentionally dehydrate yourself before you dine (this is unhealthful); or pee into a cup and sniff that. Or eat three and a half pounds of asparagus for lunch.