Steph affectionately refers to me as WebGirl, and in an effort to live up to my name, I went about researching asparagus pee this a.m. From The Straight Dope:
Serious scientific research in this field dates back to 1891, when M. Nencki tentatively identified a compound known as methanethiol as the culprit. The odor appears within an hour after eating just a few spears of the offending vegetable.According to Allison and McWhirter (1956), the ability to produce the odor is controlled by a single autosomal (i.e., non-sex-related) dominant gene. In a sample of 115 persons, 46 were rendered fragrant by asparagus and 63 were not. (This leaves 6 mysteriously unaccounted for. Urology is an inexact science, I guess.)In 1975 one Robert H. White, then with the chemistry department at the University of California at San Diego, found that the odor-causing chemical was not methanethiol after all.Instead, using gas chromatography-mass spectrometry (Bob was obviously not one to screw around), he found that the aroma was in fact caused by several S-methyl thioesters, specifically S-methyl thioacrylate and S-methyl 3-(methylthio)thiopropionate.
So, I have a mutant smelly asparagus pee gene.