Asparagus Odor Detection: 23andMe Trait of the Day

How is Asparagus Odor Detection Done?

The detection of asparagus odor in urine is entirely dependent on individual perception. After consuming asparagus, some people can detect the characteristic odor in their urine, while others cannot. It’s important to note that there are two separate phenomena at play here: the production of odorant metabolites and the ability to smell them. While most people produce the metabolites after eating asparagus, not everyone can smell them. The ability to detect the odor is highly variable among individuals.

Why Does Asparagus Have Odor?

Asparagus is a popular vegetable known for its unique flavor and high nutritional value. However, it’s also notorious for causing a peculiar odor in urine after consumption. This phenomenon, known as “asparagus odor,” results from the breakdown of asparagusic acid, a compound found in asparagus, into various sulfur-containing metabolites. These metabolites give off a strong, often unpleasant smell that’s usually described as sulfurous or similar to cooked cabbage.

Which Genes Influence Asparagus Odor?

The ability to detect the characteristic odor in urine after consuming asparagus is primarily linked to variations in a group of olfactory receptor genes. Olfactory receptors are proteins that bind to odor molecules and initiate a neural response that is perceived as smell.

The Genes

Research has identified a few specific genetic variations associated with this trait. A study published in 2010 in the journal Chemical Senses found that variations in a cluster of olfactory receptor genes on chromosome 1, specifically within a region known as 1q44, were associated with the ability to smell asparagus metabolites in urine. These genes include OR2M7, OR2M3, and OR2T33.

A subsequent study by 23andMe, published in 2016 in the journal PLOS Genetics, confirmed these findings and identified a few more specific genetic markers (single-nucleotide polymorphisms or SNPs) within this region that were strongly associated with the ability to smell the metabolites in urine after consuming asparagus.

While these genetic variants have been associated with the ability to detect asparagus odor, the relationship is not entirely clear-cut. Not everyone with these variants can smell the odor, and not everyone without them is unable to smell it. This suggests that other genetic factors may also be involved, and/or that environmental factors (such as diet, smoking, and the use of certain medications) may also influence this trait.

Explain the 23andMe Asparagus Odor Detection Report

23andMe, a consumer genetic testing company, provides a report that can predict whether you’re likely to be able to smell asparagus odor. This report is based on the presence or absence of specific genetic variants associated with this ability.

The 23andMe asparagus odor detection report is based on a study conducted by the company that identified a few genetic markers strongly associated with the ability to smell the metabolites in urine after consuming asparagus. However, like all genetic tests, it does not provide a definitive answer, as other genetic or environmental factors not accounted for in the report might also influence this trait.

Summary

References

1. Eriksson N, Wu S, Do CB, Kiefer AK, Tung JY, Mountain JL, Hinds DA, Francke U. A genetic variant near olfactory receptor genes influences the ability to smell the asparagus metabolite methanethiol. PLoS ONE. 2012;7(9):e35259.
2. Mitchell SC. Food idiosyncrasies: beetroot and asparagus. Drug Metab Dispos. 2001;29(4 Pt 2):539-543.
3. Pelchat ML, Bykowski C, Duke FF, Reed DR. Excretion and perception of a characteristic odor in urine after asparagus ingestion: a psychophysical and genetic study. Chem Senses. 2011;36(1):9-17.