Eau d’Asparagus (or What’s Behind That Asparagus Effect?)

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In Swann's Way, French novelist Marcel Proust penned something of a breathless love letter to asparagus, offering the following reflection as he ponders a decked-out dinner table:

"hat fascinated me would be the asparagus, tinged with ultramarine and rosy pink which ran from their heads, finely stippled in mauve and azure, through a series of imperceptible changes to their white feet, still stained a little by the soil of their garden-bed: a rainbow loveliness that was not of this world. I felt that these celestial hues indicated the presence of exquisite creatures who had been pleased to assume vegetable form, who, through the disguise which covered their firm and edible flesh, allowed me to discern in this radiance of earliest dawn, these hinted rainbows, these blue evening shades, that precious quality which I should recognize again when, all night long after a dinner at which I had partaken of them, they played (lyrical and coarse in their jesting as the fairies in Shakespeare's Dream) at transforming my humble chamber into a bower of aromatic perfume."

He put it as politely as anyone could. For many diners, the love affair with asparagus ends when we get to the "bower of aromatic perfume" bit while making that after dinner pit-stop. The asparagus itself, though quite tasty, later confronts you with an unpleasant smell of sulfur—that unique and cruel trick this herbaceous vegetable likes to play on our urinary system. But not everyone experiences the phenomenon. What's the deal here?

Despite several studies on the subject, no definitive evidence pinpoints which odor-causing molecules create the post-digestive asparagus smell. The most probable candidates are a few volatile chemical compounds: the colorless gas methanethiol; sulfur compounds dimethyl sulfide, dimethyl disulfide, dimethyl sulfoxide and dimethyl sulfone; and bis(methylthio)methane, which contributes to truffles' distinctive aroma and flavor. These substances are drawn out by cooking and by human metabolism and are excreted smelling a lot less like a bouquet of roses.

Curiouser still is that this trait is not universal among people. A 2010 study found that genetic factors come into play in two ways. People differ in whether and how much of the distinctive asparagus smell they produce, and people also differ in whether or not they sense the odor. Since we don't know the exact cause, figuring out who produces the smell and who doesn't remains something of a mystery—but it is surely something that will continue to inspire self-reflection and debate.

And if the above hasn't completely turned you off enjoying asparagus, we've got five ways you can prepare the stuff. What happens afterwards is your business and yours alone.

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