Asparagus and Urine Smell: The Science Behind It

Why does asparagus make your pee stink? If you’ve pondered this question, you’re not alone.

We asked urologist Tyler Trump, MD, to demystify asparagus pee’s malodorous musk. Dr. Trump explains why it happens, who it affects and if there’s anything you can do to prevent it.

What causes your pee to smell after eating asparagus?

The main culprit behind that distinctive asparagus pee smell is asparagusic acid. It’s a compound that naturally occurs in asparagus — and only in asparagus. Asparagusic acid itself doesn’t smell. But as you digest the stalky vegetable, it breaks down into sulfuric byproducts.

Sulfur, in general, isn’t very pleasant to smell.

“Sulfur is the chemical that gives rotten eggs and skunk spray their unique aroma,” Dr. Trump explains. “When you pee, those sulfur byproducts evaporate almost immediately, causing you to smell that unpleasant scent.”

Asparagus pee usually shows up between 15 and 30 minutes after eating the vegetable and hangs around for several hours. One study even found that the smell could taint your tinkle for up to 14 hours!

Not everyone has it (or can smell it)

Does everyone's urine smell after eating asparagus? The answer, it turns out, is no.

Depending on what study you read about asparagus and urine scent, somewhere between 20% and 50% of people experience this funky phenomenon. But what about everyone else? Researchers suspect that they’re missing out on the “fun” for a couple of reasons:

• Everyone digests food differently. Some people can break down sulfur byproducts more efficiently than others. In other words, it’s possible you’ve never smelled asparagus pee before simply because that’s how your body works.
• Your genes can affect your sense of smell. Some people lack the ability to detect the odor because of one (or more) variations in their genetic code. There’s even a term for it: “Asparagus anosmia.”

Is it harmful?

Asparagus pee may smell a bit disarming, but it’s still a totally normal bodily reaction.

And smelly pee’s no reason to shun the stalk. In fact, asparagus is a great addition to a balanced diet.

“Asparagus is considered a low-potassium food when consumed in small portions,” says Dr. Trump. “You can eat it as part of a healthy diet.” If you have kidney disease, you’re encouraged to eat a low-potassium diet. So, asparagus (six stalks or fewer) is a healthy choice.

It’s also worth noting that asparagus isn’t the only food that can temporarily change the smell of your pee. Some people report that drinking too much coffee causes their urine to smell like … well, coffee. Brussels sprouts, onions, garlic and soda have also been linked to odd-smelling pee in some people.

“You really only have to worry about the scent of your pee if it’s musty, sweet or has an aroma like ammonia, fruit, maple syrup or rotten fish,” Dr. Trump clarifies. “Those scents could point to an underlying health condition — especially if the smell doesn’t go away on its own within a day or so.”

Can you prevent the smell?

While there’s nothing you can do to prevent asparagus from turning your pee pungent, you can make a few minor changes to reduce its intensity:

• Drink more water. “The more hydrated you are, the more diluted your pee will be. That should help cut the odor down at least a little bit,” Dr. Trump suggests.
• Try other types of asparagus. You might be surprised by just how many different kinds of asparagus exist in the world. You may find your body breaks some varieties down better than others.
• Don’t overindulge. Eating too much asparagus in a single sitting won’t just leave you with an offensive bathroom bouquet: It can also really bother your stomach. The vegetable’s high fiber content can cause gas, bloating and stomach cramps.

Final thoughts

At the end of the day, it isn’t a big deal and it happens to many of us.

So, don’t shy away from asparagus because of urine odor. In fact, next time you smell that distinct scent, go ahead and pat yourself on the back for eating a nutritious veggie. Consider it the smell of success!