What this means

After eating asparagus, almost everyone produces the sulphur-containing metabolites (mostly methanethiol and dimethyl sulphide) that create the famous post-asparagus aroma. Whether you can smell it, though, depends on a cluster of olfactory receptor genes on chromosome 1. The rs4481887 variant is the headline SNP from a 23andMe-led GWAS of around 6,000 people; the G allele substantially reduces your odds of detecting the smell. It's one of the most charming results in modern human genetics: the production is universal, the perception is not.

After eating asparagus, almost everyone produces the same sulphurous compounds in their pee. Whether you can actually smell them comes down to a cluster of smell-receptor genes on chromosome 1. One DNA change in that cluster substantially lowers your odds of being able to detect the aroma — you produce it, you just can't perceive it. It's one of the most charming findings in modern human genetics: almost universal production, very different perception.

Caveats

• This is one of several variants near olfactory receptor genes — predictive power for any individual is modest.
• You either smell it or you don't; effect sizes here are real (not subtle).
• Most studied in European-ancestry participants.
• Truly important findings here: zero. Enjoy the asparagus either way.

References

• Eriksson et al. — Web-based, participant-driven studies yield novel genetic associations for common traits (PLOS Genetics, 2010)
• Markt et al. — Sniffing out significant pee values: genome wide association study of asparagus anosmia (BMJ, 2016)