More than 800 genes are involved in the ability to detect a rank smell in your urine after eating asparagus, researchers reported Tuesday.
The groundbreaking study may pave the way to genetic engineering that would allow more people to detect the distinctive odor, the team at the Harvard School of Public Health said.
And it may provide a way to let more people in on the health benefits of asparagus, said Lorelei Mucci, an associate professor of epidemiology who led the study.
The firmly tongue-in-cheek study is published in the mostly humorous end-of-year holiday issue of the British Medical Journal.
"Outstanding questions on this topic remain; first and foremost perhaps is why a delicacy such as asparagus results in such a strong odor?" Mucci's team asked in their report.
"And, will scientists take the results of our study and apply gene editing techniques to convert smellers to non-smellers?"
The team used two big studies of 6,900 men and women to find out why some people can smell the asparagus effect and others cannot.
"Findings show that 40 percent of participants agreed that they could smell a distinct odor in their urine after eating asparagus, and 60 percent said they could not and were labeled as 'asparagus anosmic.'"
They're pretty sure it's not a case of some people having the smell or not -- people who can't smell the asparagus effect in their own urine can't smell it in the urine of people who are known to produce the smell.
They looked through 9 million different genes to see why, and found 871 mutations in the majority of people who cannot smell the effects of eating asparagus in their own urine. "All were located on chromosome 1, containing multiple members of the olfactory receptor 2 gene family," they wrote.
Asparagus is good for you, they noted, so it may be important to help people cope with their ability or inability to smell it.
"Asparagus is rich in iron, fiber, zinc, folate and vitamins A, E and C. Consumption of asparagus, as part of a diet high in vegetables, has been hypothesized to reduce the risk of cancer, cognitive impairment and cardiovascular related diseases," they wrote.
"Furthermore, literature from the 15th century touts its aphrodisiac qualities."
It's not clear whether it's better to smell the asparagus or not to smell it.
"Future replication studies are necessary before considering targeted therapies to help anosmic people discover what they are missing," the team concluded.