Love it or loathe it, asparagus sometimes shows up on the dinner table. But there's a funny thing about this vegetable. Some people notice a telltale odor after eating asparagus while others seem oblivious to it. An AncestryDNA® Traits test can tell you if your DNA suggests you're able to detect the smell of asparagus metabolites in urine.
Why Does Asparagus Make Your Urine Smell?
Have you ever wondered, "Why does my pee smell after eating asparagus?" When your body digests asparagus, it produces a chemical called asparagusic acid. Asparagusic acid breaks down into compounds that contain sulfur, which is notoriously stinky (think rotten eggs). Some people can smell this in their urine after eating asparagus, but others can't.
Scientists used to think that asparagus caused some people to produce bad-smelling urine. However, it turns out that it's probably not the stench—but the ability to smell it—that varies. The inability to smell the effects of this vegetable is called “asparagus anosmia."
Passing on the “Asparagus Pee" Detection Gene
If you're wondering why you're able to detect "asparagus smell" in your urine, your genes have the answers. This is because non-genetic factors don’t play a significant role in this trait, so things like environment or diet aren't likely to affect whether you can or can’t smell the odor.
The ability to detect this specific and distinctive smell appears to be a dominant trait. That means if you inherited the gene variant for smelling asparagus metabolites from either of your parents, you'll probably be more sensitive to the scent of asparagus in urine. It's also likely that variants in other olfactory genes may play a role, so there may be multiple genes involved in asparagus smell detection.
Science Behind the Asparagus Metabolite Detection Trait
Scientists think the OR2M7 gene on chromosome 1 affects your ability to detect the asparagus urine smell. The gene OR2M7 produces an olfactory receptor that allows you to pick up certain chemicals in the air, like sulfur or citrus. Small differences in your DNA around OR2M7 can leave you more or less able to detect the odors asparagus adds to your urine.
A study that included 6,909 people (of European-American descent) found that 61.5% of women and 58% of men had asparagus anosmia, so they couldn't smell asparagus in urine. While women usually have a better sense of smell, scientists don't know why this is different for asparagus metabolites.
Interesting Facts About Asparagus Urine Smell
If you can get past the distinctive post-consumption smell, you'll discover that this vegetable is a nutritious powerhouse. Half a cup of cooked asparagus only has 20 calories, but it has 2.2 grams of protein. That half a cup also provides you with 57% of your daily recommended intake of vitamin K and 34% folate. Plus, asparagus has vitamin C, fiber, and vitamin E.
An epidemiologist at Harvard University, Lorelei Mucci, points out that not being able to detect the scent of asparagus in urine can be useful since you'll be more likely to eat it without having to worry about odors in the bathroom later.
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