Why does asparagus make your urine smell?

Answer 1

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.

Clearly, further research is needed.

Answer 2

Eau D'Asparagus

I love asparagus, but I notice it makes my urine smell funny. What's going on?

By Elizabeth Somer, MA,RD

Aug. 14, 2000 -- You may have heard the tall tale that "asparagus urine" is linked to higher intelligence. In fact, it's the result of a simple chemical reaction. Asparagus contains a sulfur compound called mercaptan. (It's also found in rotten eggs, onions, garlic, and in the secretions of skunks.) When your digestive tract breaks down this substance, by-products are released that cause the funny scent. The process is so quick that your urine can develop the distinctive smell within 15 to 30 minutes of eating asparagus.

But not everyone has this experience. Your genetic makeup may determine whether your urine has the odor -- or whether you can actually smell it. Only some people appear to have the gene for the enzyme that breaks down mercaptan into its more pungent parts. A study published in the May 1989 British Journal of Clinical Pharmacology found that 46% of 115 people tested produced the odor in one group of British citizens, while 100% of 103 people produced it in a group of French citizens. The ability to smell the by-products may also be genetic. Another study published in the same journal found that 10% of a group of 300 Israeli Jews could not detect the odor. In other words, a person's urine could smell, but he or she might not know it. Judging from your question, you can do both. But that's nothing to worry about.

While eating asparagus may make your urine smell strange, it won't harm you. Actually, asparagus -- a member of the lily family along with garlic, onions, and leeks -- is a powerhouse of nutrients. It's an excellent source of folic acid (a B vitamin that may help protect against birth defects, heart disease, and cancer), a significant source of vitamin C (an antioxidant that may protect tissues against damage), and a good source of vitamin A (an antioxidant). Not to mention that asparagus contains 3 grams of fiber per 3.5-ounce serving and a host of health-enhancing plant chemicals, or phytonutrients, that may protect against disease.

Although the link between "asparagus urine" and higher intelligence is a figment of someone's imagination, eating it regularly could be a sign of some serious health smarts.

Elizabeth Somer, MA, RD, is the author of Nutrition for a Healthy Pregnancy, Food & Mood and The Essential Guide to Vitamins and Minerals, and co-author of The Nutrition Desk Reference. An advisory board member to Shape and a contributing editor to Eating Well magazine, she has appeared on The Today Show, The View, CBS This Morning, and other television and radio programs.

Answer 3

There is a compound in asparagus that everyone metabolizes into the smelly compound that ends up in urine. Only some people have the gene that allows them to smell it, though.

Answer 4

at least a cow has a chance to run away, but you have to slaughter the poor old asparagus, who is just stuck there in the ground and doesn't stand a chance. butcher! i say. on a serious note, take a vitamin b complex and you get glow in the dark pee, lol

Answer 5

the better question is, y r u smelling ur piss?