Sunday, June 16, 2019

Plant Story--Garden Asparagus, Its Folklore and "Asparagus Pee"

red asparagus shoots

Garden asparagus (Asparagus officinalis, asparagus family, Asparagaceae) has been cultivated since Roman times (see last week's post link), so there is interesting folklore.

It was and is considered an aphrodisiac. It comes up as phallic shoots in the spring. Historically and prehistorically people celebrated spring as a rebirth and time of renewed reproduction. Asparagus shoots fit well into that. Cultures from Greece to England have included asparagus in spring (fertility/Easter) festivals, both as food and in decorations from bouquets or chaplets (little wreaths worn on the head).

Apart from symbolism, asparagus shoots are one of the earliest vegetables of spring. If you imagine Europeans living all winter on dried peas and pickled cabbage, having fresh vegetables would not only be a delight, it would provide nutrients that were likely missing in the winter diet, so indeed fresh asparagus would act as an aphrodisiac.

Dioscorides, author of a very influential book on medicinal plants in 64 C.E., wrote that people plant small pieces of ram's horns and asparagus comes up, which he doubted.

Dioscorides also reported that if dogs drink the seeds in water they will die. The red fruits are slightly toxic: 5-7 will cause vomiting and abdominal pain in humans (link) though I can find no reports of fatalities in humans or asparagus seed toxicity in dogs. The plants do cause dermatitis in some people.

asparagus plants

Dioscorides further said that hanging an asparagus shoot around the neck as an amulet, and drinking a decoction ("tea") of the shoots, it will make the person barren.

A thousand years later, the Tacunium Sanitatis, a health handbook that began in Arabic about the year 1000 but was reproduced in Italy and France in the 13th and 14th centuries, recommended gathering young stalks whose tips point downward, which, when eaten, make one's humors flow unobstructed and stimulate carnal relations. Gerard (1633) likewise said eating asparagus was thought to increase seed (semen) and provoke lust.

The Tacunium Sanitatis also wrote:

"Avicenna, the learned Persian savant, said that [asparagus] imparts a pleasing smell to the whole body"

Which brings us to the question of asparagus pee. If you have not experienced it, many people smell a distinctive odor in their urine after eating asparagus. Avicenna may have liked it but Franklin did not.

Benjamin Franklin (1781) (in Fart Proudly) wrote "A few Stems of Asparagus eaten, shall give our Urine a disagreable Odour;" 

Proust is poetic but I read him as disliking the odor:

“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 recognise 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 chamberpot into a bower of aromatic perfume.”― Marcel Proust, Swann's Way 1913 (from Goodreads website).

So the scent asparagus imparts to some people's urine has been known a long time. Mitchell (see references) says the odor wasn't reported until the 18th century (by John Arbuthnot, physician to Queen Anne of Englandabout 1731). But he also points out that there is a problem with reporting:
   "Those who produce the odor assume, politely, that everyone does and those who do not produce it have no idea of the olfactory consequences. There is no reason as to why these two opposing factions should converse on this subject. A brief discourse with one's colleagues will confirm such differences and verify this state of affairs." (p. 541) So no one thinks to bring up the subject. Surely that applied historically as well. 
asparagus shoots

Today, though, it is an active area of research. 

There's probably a search on for a delicate way to say "smelling a distinct odor, somewhat like rotten cabbage (also reported to smell like vegetable soup) in your urine after eating asparagus" but "asparagus pee" is the current term. As a child, when I discovered it, I thought it interesting, not repulsive. My brother-in-law, however, found it sufficiently revolting that he will not eat asparagus.

When I was a college student in the 1970s, the explanation was that some people broke down the compounds in asparagus to small volatile molecules and some did not (or broke them down more). That turns out to be only part of an ongoing story.

People smell their own pee, but not other people's (usually). It turns out that some people can smell the volatiles in asparagus pee, and some cannot. So we have asparagus anosmia (inability to detect the smell) and those who are not asparagus anosmic (can smell the odors). (I said there was a search for euphemisms).


Both producing asparagus pee or not and smelling it or not have been reported to have a genetic basis. The assumption has been that to smell asparagus pee you have to have the genes that put the smelly molecules into urine and then have the genes to smell those molecules. Certainly both traits (excreting/ detecting) vary across the people so far studied. Human Genetics Myths has a very nice analysis (link). 

The research community is working on understanding asparagus pee but has a long way to go. Issues not yet resolved include
     >dosage effects--what concentrations of smelly molecules do people normally smell and how much does that amount vary between people (both creating more smelly molecules per asparagus spear eaten and concentration necessary to be detected)
     >what exactly are the compounds people smell? Those have to be only in asparagus, survive cooking and eating, and be small enough to disperse into the air, so there's no definitive answer yet on which molecules
     >how are the abilities to create asparagus pee and to smell it inherited--or are they?  The explanation that all the variation is due to the method of asparagus preparation, amount eaten and conditions for digestion is hard to eliminate given the wide variety of methods in studies to date. If genetic, how many people (what percent) have the genes (alleles) that create asparagus pee and what percent can smell asparagus pee? Can most of the people who make asparagus pee also smell it?
     >And, is the ability to make or smell asparagus pee a benefit or a liability?

Sounds like we don't know much at all.

Almost certainly, making asparagus pee and smelling it are different groups of genes. The asparagus pee gene may be inherited as a simple dominant (if you get one copy you will make asparagus pee) but there is inadequate data on transmission in families. The ability to smell appears to be more complex, but no inheritance data is available. Of people who have been asked, mostly northern European or Americans of that ancestry, about 40% made asparagus pee and about 40% could smell asparagus pee. But inability to smell asparagus pee was far the most common condition in Israeli and Chinese studies. The details and sample sizes differ greatly between studies so it is impossible at this time to say anything about the number of people who produce asparagus pee and the number who can smell it, and certainly not about how many people can do both. (Though Franklin and Proust surely did).

And of course we would like to know what the chemistry is of making or not making asparagus pee. And beyond that, to know what differs biologically and chemically between people who do and do not smell asparagus pee.

This is an active area of research: watch the science news for answers to the questions above.

Whatever your asparagus pee and asparagus pee smelling characteristics, enjoy being you. And try that conversation with coworkers: does everyone indeed assume that their own excrete/detect condition is universal?

asparagus in a vase

And look, writing these posts results in serendipity. Isn't the asparagus beautiful in a vase?!

Comments and corrections welcome.

Note: asparagus pee is a good topic for student papers: a modest-sized literature with lots of questions available, methods that differ so the reader must be very careful making comparisons, several papers critiquing the methods previously used and the opportunity to test any hypothesis by feeding asparagus to friends and family.

Gerard, J. 1633. The Herbal or General History of Plants. Dover edition, New York. 1975.
Gunther, R. T. 1934. The Greek Herbal of Dioscorides. Oxford University Press, Oxford.
Markt, S. C., E. Nuttall, C. Turman and others. 2016. Sniffing out significant 'Pee values": genome wide association study of asparagus anosmia. The BMJ. (British Medical Journal) Dec 2016. published online.
Markt, S. C. and L.A. Mucci. 2017. Authors' reply to Rishniw. BMJ : British Medical Journal 
(Online); London Vol. 357,  (Jun 16, 2017). link
McDonald, J. H. 2011. Aspargus urine smell: The myth. Myths of Human Genetics. visited 6/8/19. The citation the site gives is pp. 8-13 in: McDonald, J.H. 2011. Myths of Human Genetics. Sparky House Publishing, Baltimore, Maryland. Very nice summary, up through 2011.
Ramamoorthy, A., B. M. Sadler, J.G. Coen van Hasselt and others. 2017. Crowdsourced asparagus urinary odor  population kinetics. CPT Pharmacometrics Syst. Pharmacol. 1: 34-41. link.
Mitchell, S. C. 2001. Food idiosycracies: beetroot and asparagus. Drug Metabolism and Disposition 29: 539-543.
Rishniw, M. 2017. "Perception v production" of asparagus odour in urine needs to be determined in a controlled study. BMJ (British Medical Journal) 2017: 357L j2882 (link)
Spencer, J. translator. 1983. The Four Seasons of the House of Cerruti. Facts on File Publications, New York. (a translation of the Tacunium Sanitatis)

Kathy Keeler, A Wandering Botanist


  1. Thank you for sharing

  2. Love the history, thank you. BTY, when one sends a cell sample to 23andme,
    one of the genetic markers tested for is Asparagus Odor Detection!