Seeking asparagus info

Peter Rice rice at
Wed Mar 9 03:18:05 EST 1994

In article <2ldrhe$6g0 at>, piggy at
(La Monte Yarroll) writes:

> There is something in aparagus which causes a specific odour in urine
> in certain individuals.  Does anybody know what this substance is?
> We would appreciate any information on asparagus or related species.

With apologies to the rec.gardens readers, because this has little to do with
gardening - but it was a cross-post and the answer is amusing.

This is my favourite search of the human genetics database OMIM (Online
Mendelian Inheritance in Man). There is something that causes a smell, *but*
it does it in all individuals. The genetic difference is that not everyone
notices the smell.

The two relevant OMIM entries, both fairly short, are included below.

In case anyone worries about the "groups of ethnic jews" reference, OMIM
frequently cites population studies of isolated groups, usually in whichever
country the studies were carried out. If you search OMIM with the name of any
country, you are sure to find some strange genetic differences associated with
them. For example, the relative length of big and second toes in Cleveland
Ohio, Sweden, and other populations varies dramatically.

The "I" in the first entry is Victor McKusick, who wrote a lot of the database.
(For a further self-reference, try looking up Kirk Douglas in OMIM :-)

>The odoriferous component seems to be methanethiol.  Forty-six of 115
>persons were excreters in the experience of Allison and McWhirter
>(1956).  They suggested, furthermore, that 'excreter' is dominant to
>'nonexcreter.' I am told (Maas, 1972) that a nonexcreter may become
>an excreter during pregnancy, the unborn child presumably being an
>excreter.  This is yet to be tested.  Lison et al. (1980) concluded
>that the urinary excretion of an odorous substance after eating
>asparagus is not an inborn error of metabolism, but rather that the
>detection of the odor constitutes a specific smell hypersensitivity;
>see 108390.
>Allison, A. C. and McWhirter, K. G.: Two unifactorial characters for
>which man is polymorphic. Nature 178: 748-749, 1956.
>Lison, M.; Blondheim, S. H. and Melmed, R. N.: A polymorphism of the
>ability to smell urinary metabolites of asparagus. Brit. Med. J. 281:
>1676-1678, 1980.
>Maas, W. K.: New York City: personal communication, 1972.

>Lison et al. (1980) concluded that the urinary excretion of an
>odorous substance after eating asparagus is not an inborn error of
>metabolism as had been supposed (see 108400).  Instead they suggested
>that the detection of the odor constitutes a specific smell
>hypersensitivity.  Their observations on a large number of
>individuals indicated that those who could smell the odor in their
>own urine could also smell it in the urine of anyone who had eaten
>asparagus, whether or not that person was able to smell it himself.
>Thresholds for detecting the odor appeared to be bimodal in
>distribution, with 10% of 307 subjects tested able to smell it at
>high dilutions.  No family studies were reported.  There were no
>differences in the distribution of smellers and nonsmellers for this
>specific odor in the 3 ethnic groups of Israeli Jews studied.
>Lison, M.; Blondheim, S. H. and Melmed, R. N.: A polymorphism of the
>ability to smell urinary metabolites of asparagus. Brit. Med. J. 281:
>1676-1678, 1980.

 Peter Rice, EMBL                             | Post: Computer Group
                                              |       European Molecular
 Internet:    Peter.Rice at EMBL-Heidelberg.DE   |            Biology Laboratory
                                              |       Postfach 10-2209
 Phone:   +49-6221-387247                     |       69012 Heidelberg
 Fax:     +49-6221-387306                     |       Germany

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