Myths about asparagus urine smell

pp. 8-13 in: McDonald, J.H. 2011. Myths of Human Genetics. Sparky House Publishing, Baltimore, Maryland.

Asparagus urine smell: The myth

As stated in this article written by John H. McDonald, Ph.D., Professor, Department of Biological Sciences, University of Delaware,

After they eat asparagus, some people notice that their urine has a strong, unusual odor. Other people don't notice anything unusual. This was first thought to result from genetic variation in whether or not sulfur compounds in asparagus were secreted into the urine, with the allele for secreting being dominant. Later it was suggested that everyone secretes the compounds in their urine, but only some people can smell the compounds.

After citing works from renowned experts dating from 1950s through 2011, McDonald seems to be saying what we as sufferers have discussed in meetups amongst ourselves and have experienced in our own lives - that "in addition to variation in excretion, there is also variation in the ability to smell the compound," as Dr. McDonald states in this article. He adds,

This complication means that the ability to smell stinky compounds in one's own urine after eating asparagus is not a simple genetic trait. It is not known whether the two separate traits, secreting the compounds and being able to smell them, have a simple genetic basis.

This blog has made reference in posts listed below to the dichotomy sufferers have to deal with on a regular basis - some argue that a particular sufferer is not emitting odor at any given moment in time, while at the same time, others are offended by the odor. This phenomena makes everyday life a very torturous ordeal because a sufferer never knows who does or does not perceive the odor, and thus, what reaction to expect from others. Consistency in social reaction to one's behavior or one's appearance, helps maintain a sense of control and security. This sense of control and security erodes in the life of sufferers because of the unpredictability of people's reactions due to the varying degrees of olfactory sensitivity. Slowly but surely, normal psychological reactions to feeling out of control and vulnerable begin to creep in, such as anxiety and depression, and ultimately, social isolation. Moreover, personal relations are strained when loved ones deny the existence of odor and suspect mental illness is the cause of the "imagined" odor.

When trying to understand whether a person suffers from body odor/halitosis, the following questions need to be addressed:

1. Are odorous compounds are present or not? Of course, this should be established by scientific tests that identifies and quantifies the compound(s).
2. Is it that they are present on an intermittent basis? Possibly triggered by diet, mood/mental state, hormonal changes, weakened metabolic, etc.
3. Is it that only some people who have a keener sense of smell can detect it, while others cannot? "Beauty is in the eye of the beholder, as well as "Odor is in the nose of the beholder."

It is refreshing to read Dr. McDonald's Conclusion:

It is clear that there is variation in two different traits: excretion of sulfur compounds in urine after eating asparagus, and ability to smell those compounds. This means that asking people whether their own urine smells odd after they eat asparagus is not a good way to study this. The limited amount of family data available suggests that excreting may be a simple one-gene character, with the allele for excreting dominant, but more work needs to be done. There is no family data on the smelling/non-smelling trait, only the genomic association study of Pelchat et al. (2011), so more work needs to be done on this trait as well.

Scroll down to read all the related articles in this blog under the following links:

• Anosmia
• Olfactory
• Olfactory Reference Syndrome

María

María de la Torre
Founder and Executive Director

A Public Charity
www.meboresearch.org
www.brasil.meboresearch.org
maria.delatorre@meboresearch.org
MEBO's Blog (English)
El Blog de MEBO (español)
MEBO Brasil - Blog (Portuguese)

---

SUPPORT THE MEBO MISSION: Click Amazon button at right sidebar of this blog when shopping online for the holidays
at no extra cost to you.
MEBO gets small commission from Amazon.

Please use your credit card to make your donation to MEBO.

Subscribe for latest posts : Enter your email address:

Delivered by FeedBurner

---

A EURORDIS and NORD Member Organization