Smelly Urine; but why?

Sometimes, especially late at night, I am surprised to find that my urine smells like . . .

-Popcorn

-Bacon Cheeseburgers

-Thumb tacks

-Dry Wall

(I kept a running list next to my sink over the last week. After researching this a little bit, I have concluded that I have genetic super-powers; not involving my digestive tract, but with my nose ––– It's ultra-sensitive. Sensitive to a fault. I have not yet discovered how to apply this power for the benefit of humanity.)

Why does urine smell like different things?

Disease:

According to WebMD, "Urine does not smell very strong, but has a slightly "nutty" odor. Some diseases cause a change in the odor of urine. For example, an infection with E. coli bacteria can cause a bad odor, while diabetes or starvation can cause a sweet, fruity odor."

Why does urine smell nasty after eating asparagus?

History:

There is only one recorded instance in which a food had a repeated effect on urine odor. In the 18th century, a physician to the French royal family wrote in his Treatise on all sorts of foods that asparagus "eaten to Excess... causes filthy and disagreeable Smell in the Urine." (McGee H. On food and cooking: the science and lore of the kitchen. New York: Simon & Schuster, 1997;194.)

Allison and McWhirter first showed that the ability to produce methyl mercaptan after eating asparagus is not universal. (Allison AC, McWhirter KG. Two unifactorial characters for which man is polymorphic. Nature 1956;178:748-9.)

The Biochemical Mechanism:

The smell cannot be noticed in raw or cooked asparagus, so it is believed that the body converts a compound within asparagus into a metabolite, which can then be smelled in the urine. The odour is often described as the smell of rotten or boiling cabbage, or even ammonia, and is believed to be due to the presence of methyl mercaptan, also known as methanethiol, which is a sulphur containing derivative of the amino acid methionine. (Nencki M. Uber das Vorkommen von Methylmercaptan in menschlichen Harn nach spargelgenuss. Arch Exp Path und Pharmak 1891;28:206-9.)

Experiments:

Some people produce detectable amounts in the urine after eating only three or four spears of asparagus, while others would produce none even after eating as much as one pound (0.45 kg) of asparagus. In original test's random sample of 115 human subjects, they demonstrated that this ability occurred in about 40% of the population, with an autosomal dominant inheritance pattern. (Allison)

In a larger study of 800 volunteers, Mitchell and co-workers verified these findings in both men and women, and from a pedigree analysis of two families, with one spanning three generations, the autosomal dominant mode of inheritance was also confirmed.5 Interestingly, the BM Journal later reported a study in which all the subjects could produce methyl mercaptan, but their ability to smell it in the urine differed. Those who were able to smell the odour in their own urine could smell it in the urine of anyone who had eaten asparagus irrespective of whether or not that person could smell it. The authors suggested that the ability to smell these substances in one's or, indeed, another's urine was also genetically determined. (Lison M, Blondheim SH, Melmed RN. A polymorphism of the ability to smell urinary metabolites of asparagus. BMJ 1980;281:1676-8. 7 White RH. Occurrence of S-methyl thioesters in urine of humans after they have eaten asparagus. Science 1975;189:810-11.)

Apart from methyl mercaptan, other metabolites may be responsible for the smell of the urine after eating asparagus. Gas chromatography of the urine has shown that the odour could be caused by S-methyl-thioacrylate and S-methyl-3- (methylthio)thiopropionate,7 while a combination of methyl mercaptan, dimethyl sulphide, and small amounts of sulphur-oxidised compounds could also be responsible.8 The source of these metabolites is unknown, but the last paper postulates asparagusic acid, which is specific to asparagus and, when given to humans, causes the same characteristic smell in the urine.8

Apparent Cure

Drink more water. This should simply dilute the solution before passing through the kidneys, making the scent less strong.

p.s. I don't eat thumb tacks or dry wall.