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Dear Cecil:
My faith in you remains unshaken and my respect for the
sagacity of your judgment undiminished. However, I am afraid that,
as Mitzi Malone might say, your interlocutors have gotten pretty
weenie.
What you need are some good questions, such as the
following: Why does my urine smell funny after I've eaten
asparagus? --F.K., Dallas, Texas
Dear F.:
I have probably been asked
this question a dozen times since I started this job. The first
ten times I dealt with it as you might expect. I burned the letter,
had the room fumigated, and prayed for the writer's immortal soul.
This week, however, I have
gotten the question twice in the same mail. This leads
me to believe this is something the Teeming Millions truly
yearn to know, God help us. So I give up. Here's the story:
Many sagacious
persons have noted the peculiar effect of certain products on human
urine.
For example, Benjamin Franklin, in a wide-ranging discussion
of bodily discharges, once noted, "a few stems of asparagus eaten
shall give our urine a disagreeable odor; and a pill of turpentine
no bigger than a pea shall bestow upon it the pleasing smell of
violets."
It is said that in a venerable British men's club there
is a sign reading "DURING THE ASPARAGUS SEASON MEMBERS ARE
REQUESTED NOT TO RELIEVE THEMSELVES IN THE HATSTAND."
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.
(Thioesters are
compounds that result from the reaction of an acid with a
sulfur-containing alcohol. They tend to be smelly.)
I know you are
very interested in all this stuff and are following me closely, F.,
so I am going to give you the exact chemical formulation for these
chemicals, in case somebody asks you at some fancy social soiree.
The thioacrylate recipe
is:
CH2=CHC(=O)SCH3
The thiopropionate
is:
CH3SCH2CH2C(=O)SCH3
We are faking the above somewhat given the limitations of the ASCII
character set, but I know you are grateful for whatever information
we can provide.
Anyway, sez Bob, the "metabolic origin [of the compounds--i.e.,
how and why they end up in the urine] remains an open question." I
can't exactly say that research is continuing, but if anything
develops I'll let you know.
--CECIL ADAMS
The Straight Dope / Questions or
comments for Cecil Adams to: cecil@chicagoreader.com
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