text: why does eating  asparagus make your urine smell funny?   "as you clearly know, the human digestive processes are typically able to break asparagus down into smelly by-products with an amazing quickness, often within 15 to 30 minutes after eating. when you use the lavatory, those odorific by-products are released as a rather pungent form of "asparagus urine."   the website webmd blames this smell on the break-up of a chemical called mercaptan. that said, asparagus contains a half-dozen sulfur-based chemicals identical ones found in other such lovely smells as rotten eggs, garlic breath and skunk spray. there is some controversy in the scientific community over exactly which by-product, or combination of by-products, causes the asparagus urine smell. the first published study on the phenomenon, written in 1891 by a man going by the name of "nencki," found that the smell was caused by a metabolite called methanethiol. so far, this conclusion seems about as sound as any.  but the story of asparagus urine is far from ending there. some people eat asparagus, go to the restroom, and-amazingly-no smell. further research suggested that, likely due to genetics, some people did not possess the enzymes required to create asparagus urine. perhaps you've heard it said that a person who's pee smells after eating asparagus has high intelligence? well, maybe there is some genetic corollary for that. (just kidding, all you eugenicists out there!)   to complicate matters even further, however, around 1980 a scientist had the good sense to pass the urine of the non-asparagus urine population in front of the noses of the asparagus urine population, and lo-and-behold, many found they could smell that asparagus urine smell. people are now debating whether genetics controls the ability to produce asparagus urine, the ability to smell asparagus urine, or possibly both."   http://www.greenworks.tv/askgreenworks/asparagus.htm