Why does eating asparagus make my urine smell so bad?

Asparagus is a surprisingly popular vegetable, and for good reason: it's crunchy, earthy, and scrumptious. As an additional culinary option, the vegetable can be used in a wide variety of dishes, including cold soups, salads, frittatas, and more. One major caveat One reason to avoid asparagus is the unpleasant odor it can impart to your urine. Several authors, including Benjamin Franklin, have referenced the odor of "asparagus pee" in their works over the centuries.

But why, exactly, does eating asparagus cause you to urinate so strongly? The scientific explanation for asparagus peeing and the ability to smell it has been discovered. Here, registered dietitians explain why and how asparagus causes a person's urine to smell. (

Foreground on what asparagus is and isn't is necessary before delving into why it causes a pungent urination odor. As reported by the University of Illinois, asparagus is a spring vegetable that originated in the Mediterranean and is related to onions, leeks, and garlic. A scientific review published in the journal Metabolites in 2020 revealed that there are approximately 300 cultivars of asparagus, including green, purple, white, and pink colors. On the other hand, in the United States, green asparagus is the norm. S you can find the green "Martha Washington" variety's stems (also known as spears, the edible part of the plant) in most supermarkets.

However, consuming asparagus of any variety has been linked to the development of "asparagus pee," or particularly pungent urine. This is not a technical term, but the phenomenon is so common (and smelly) that it has entered the vernacular. Urine doesn't typically have a pleasant aroma to begin with, but asparagus pee stands out due to its particularly strong odor, which has been compared to that of rotten eggs and garlic, according to Annamaria Louloudis, M.S., R.D., a registered dietitian at Culina Health. Depending on how sensitive your nose is, you may also detect a sour, acidic, or tart aroma. When translated literally, that means the odor is absolutely repulsive.

If the smell of asparagus in your urine gives you pause, just remember that it's a natural byproduct of digestion. The "chemical compound" in asparagus, as explained by Louloudis, is "asparagusic acid." According to studies, eating asparagus causes your body to produce compounds rich in sulfur. (Sulfur, by the way, is a chemical element that, surprise, smells like rotten eggs.) Odorous pee results from the excretion of these compounds and other waste products through the urinary tract. Also, as Louloudis puts it, "sulfur-containing molecules [readily vaporize at room temperature], allowing them to easily travel from urine into the air." So it's understandable if you find yourself scrunching up your nose even before you flush the toilet.

Rapid asparagus urination is also possible. About 15 to 30 minutes after eating the vegetable, you may notice an unpleasant odor in your urine, and according to Louloudis, that smell may linger for up to 14 hours. However, as Ehsani points out, the length of time you experience asparagus pee depends on a number of factors, including how much asparagus you ate and how often you urinate. To reduce the duration of the unpleasant smell of asparagus pee, Ehsani suggests maintaining a healthy fluid intake and urinating more frequently. However, she qualifies this by saying that how your body handles asparagus plays a role and that this varies from person to person. (We'll get to that last part in a minute.) )

Right about now is when things start to get exciting. "Not everyone develops smelly pee after eating asparagus," says Roxana Ehsani, M.S., R.D., C.S.S.D., L.D.N, so don't worry if you don't notice a change after eating asparagus. professional nutritionist She explains that this is because some people may be better able to metabolize the sulfur-containing compounds (once again, a byproduct of asparagusic acid in asparagus) than others. However, there is currently no research explaining why some people may be better at metabolizing these compounds than others. As a result, it's possible that people whose diets include asparagus will produce less sulfur-containing compounds in their urine, resulting in less pungent urination.

Other times, it has less to do with digestion and more to do with your sense of smell. Asparagus anosmia, as described by Ehsani, is the inability to detect sulfuric byproducts in one's urine even if they are produced after eating asparagus. (For those who might not know, anosmia refers to a lack of olfactory sensitivity.) According to Ehsani, the inability to smell the sulfurous odor of asparagus is due to a genetic variation that alters olfactory (smell) receptors. Even if your urine contains post-asparagus sulfuric compounds, you may not notice a difference in the smell from a healthy individual.

Your reaction to asparagus pee may also be influenced by other factors. For instance, a 2016 study published in the journal BMJ found that urinating while seated may reduce exposure to odorous compounds, making it less likely that people will notice the odor. Ehsani suggests that a low level of sulfur-containing compounds in the urine could be the cause. She explains that this is possible if you eat a lot of other things in addition to the small amount of asparagus you're supposed to eat. She gives the example of eating a small amount of asparagus, saying that "if you eat a small amount of asparagus — just a spear or two [in] a large veggie medley," the concentration of sulfur compounds in the urine would be so low that the smell might be undetectable. Similarly, if you drink a lot of water, you may not notice as strong of a stench because your body will be excreting the compounds more quickly.

There's no way around it, says Louloudis; your urine will smell bad if you eat asparagus. First of all, you can't stop your body from producing sulfuric compounds because of the way it digests food. You can't alter your olfactory receptors' sensitivity to odorous molecules because doing so would require altering your genetic make-up, which is beyond your control. But if you drink more fluids and then pee more frequently, the unpleasant compounds will be flushed out of your system more quickly, and you'll have a more pleasant urinating experience overall. Another way to lessen your contact with these noxious chemicals is to urinate and flush while seated.

It's important to keep in mind that passing urine shaped like an asparagus is totally normal. However, according to Ehsani, this does not make the vegetable in question "unhealthy" or cause for widespread avoidance. She further clarifies, "You can — and should — eat asparagus even if you have smelly pee after." After all, asparagus is loaded with useful nutrients like fiber for maintaining a healthy digestive system, vitamin K for strong bones, and folate for promoting a healthy pregnancy. Even if you have to pinch your nose after you urinate because of the smell of asparagus, it's worth it because of the health benefits.