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| A bundle of asparagus. Photo by Evan-Amos on Wikimedia. CC BY-SA 3.0. |
In Germany, in the spring, everyone goes wild about asparagus. It is on the menu in all restaurants—asparagus with steak, with ham, or with schnitzel. Its delicious stalks are white if grown in the shade, green from chlorophyll if grown in sunlight. Asparagus is also eaten outside Germany, but perhaps not quite with the same passion. You can now buy it all year round in cans that decades ago were unreasonably expensive.
Asparagus is a distant cousin of the onion and garlic. The name came from Greek to Latin, perhaps from Persian to Greek, from Latin corrupted to sperage or sparrow grass. It was cultivated for at least 2,000 years in eastern Mediterranean countries, in Egypt, and the rest of Africa. In ancient Greece, it was considered a sacred plant with aphrodisiac properties. Hippocrates used it for diarrhea and urinary complaints; perhaps its asparagine components have diuretic properties.
Caesar’s legions brought asparagus from the Middle East to Rome. The Romans enjoyed it as an entrée or as a vegetable accompanying fish. The Arabs continued to eat it. It was forgotten in Europe during the Middle Ages, then rediscovered and served at royal courts. In 17th century France, it was cultivated for Louis XIV, who was very fond of it. By the 18th century it had become fare of the common people. It is now widely eaten, in soups and salads, or with meat and fish dishes, and is produced in great quantities in China.
There is nothing unhealthy about asparagus. It is high in fiber, low in fat, full of vitamins and folate. It is not fattening. Half a cup provides only 20 calories and 2.2 grams of protein. It also contains many substances whose function in the body is unclear: flavonoids, glutathione, polyphenols, quercetin, isorhamnetin, kaempferol, and anthocyanins. In the Linnean classification asparagus was formerly placed in the lily family, with leeks, onions, and garlic, but more recently it has been reassigned to the Asparagaceae family, the Asparagoideae subfamily, and the Asparagus genus of about 300 species. Of these Asparagus officinalis is the one consumed in most parts of the world. It must not be confused with Asparagus racemosus, a plant used in Ayurvedic medicine.
In 1702 the French botanist and chemist Louis Lémery wrote that asparagus spears “cause a filthy and disagreeable smell in the urine, as everybody knows.” In 1781 Benjamin Franklin wrote that “a few stems of asparagus eaten shall give our urine a disagreeable odor” and hoped that scientists would discover a drug to render this as agreeable as perfumes. It is now known that asparagus contains asparagusic acid, an odorless sulfurous compound that is metabolized in the body into sulfur-containing compounds such as methanethiol and dimethyl sulfide. These compounds are responsible for the distinctive smell which may be detected within fifteen minutes and may persist for several hours. Everybody who eats asparagus produces asparagusic acid and its byproducts, but not everyone is able to smell them.
Several groups of investigators have studied this issue of asparagus urine, but results are inconclusive. Some people seem to have developed alternative metabolic pathways of breaking down the asparagusic acid degradation products. The urine of these “non producers” does not have an unpleasant odor.
Other people, however, do produce “asparagus urine” but cannot smell it. Some can smell it only slightly, others not at all and are sometimes referred to as asparagus anosmotics. Genetic studies indicate they were born with variations in their olfactory protein-coding genes (in OR2M7). An estimated 871 variations in the DNA sequence seem associated with asparagus anosmia. They are located on chromosome 1, the chromosomal region that contains several genes connected to the sense of smell. So it seems that we are left in the world of “asparagus urine” with some who cannot not produce it and some who cannot smell it. The latter seem to include some women who say they cannot smell it, but this is because of the position they assume during urination.
Asparagus also plays a role, perhaps largely apocryphal, in the history of kidney failure. It was said that during the last years of the 19th century, when laboratory tests were primitive, some astute clinicians would diagnose kidney failure by noting that their patients no longer produced asparagus urine. This time passed long ago, now leaving asparagus to the few who study it and the many who enjoy eating it. Surprisingly, asparagus has even been used as an ingredient to make ice cream. Marcel Proust did not object to its smell. Instead, he wrote that it transformed his humble chamber into a bower of aromatic perfume.
, MD, Editor-in-Chief
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