why does asparagus make your urine smell?

Question

not a pleasant question I know...but nonetheless,, i think its an intriguing one.

Answer 1

Im not in the habit of sniffin it..... try beetroot...that gets a good result too.

Answer 2

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, 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.

Basically it comes from the sulfur containing parts (thiols and thioesters) that are in asparagus that get quickly metabolized.

Answer 3

This is an inherited characteristic. There is an amino acid in asparagus called asparagine. Some people , depending upon their genetics, metabolize this amino acid differently than others. The waste product of this amino acid is removed from the blood by the kidneys and ends up in the urine. It has a distinct odor. Ask blood relatives if they can detect this odor after eating asparagus.

Answer 4

Asparagus is filled with sulfur-containing amino acids that break down during digestion into six sulfur-containing compounds. These can impart a unique smell to urine as they are excreted.

Answer 5

The smell is caused by various sulfur-containing degradation products (e.g. thiols and thioesters) contains in the asparagus.

Answer 6

I have no idea but you are right it's a disgusting smell. I look forward to someone answering this with a valid reason!

Answer 7

I have never tried this before however I have sent my PA out to buy € 50 worth of this magic veg and will report to you by the afternoon. Did you know that certain mushrooms make me fly .......Tally Ho...!!

Answer 8

It breaks down into sulpher containing compounds in your stomach- thats what makes your wee smell horrible!

Answer 9

I would imagine it's the complex acids in it. Apparently your emissions will taste absolutely revolting too. So I heard...

Answer 10

not sure but sugar puffs do the same