Why does the urine smell so funny after eating asparagus?

Maybe you know it yourself or from stories told by others. You eat asparagus, go to the toilet a few hours later and wonder why the urine smells so strong or even stinks. What is the reason for this and, above all, why does not everyone feel the same way? I will answer these questions for you in this post!

The aspartic acid is to blame

When it comes to something smelly in food or excreta, you can be almost certain that sulfur or sulfur compounds are somehow involved. For example, they are also significantly involved in the strong smell of eggs or any other decomposition processes.

In the case of asparagus, the culprit is what is known as aspartic acid. This is a sulfurous carboxylic acid found in common asparagus.

Aspartic acid is broken down in the body after eating asparagus and converted into various other compounds. Among other things, this produces sulfur-containing compounds that are excreted through the hard and are therefore responsible for the unpleasant smell.

That’s why not all urine smells the same

Now you know where the smell in the urine after eating asparagus comes from. But why doesn’t everyone notice the smell immediately and why are there many people who don’t smell any stench after eating?

The breakdown of aspartic acid depends heavily on which enzymes are present in the body and in what ratio and are involved in the breakdown. Which enzymes you actually have or don’t have depends on various influencing factors. An important aspect is genetic disposition. This ensures that the breakdown products of aspartic acid differ from person to person. About 40% of people from the sulfur compounds are responsible for the characteristic smell. All others do not form these or only to a very small extent. Exactly why this is the case is the subject of current research.

Everyone smells different!

Another important factor to consider is that each person perceives smells very differently.

For example, the threshold for what we perceive as “smelly” is different for everyone. The sulfur-containing decomposition products are perceived differently by everyone.

What is special about the sulfur-containing decomposition products in asparagus is that there are people who do not (cannot) perceive these smells at all! This is due to a genetic mutation of an olfactory receptor that causes those specific scents to go undetected. If you are interested in the topic, you can find a lot more information under the keyword anosmia.

That’s why the urine stinks after eating asparagus

In summary, there are two reasons why some people’s urine smells strong after eating asparagus, while others (almost) don’t smell at all.

The sulfur-containing degradation products of the aspartic acid contained in asparagus, which are responsible for the unpleasant smell, are formed and excreted by each person in different amounts and compositions. The form in which this happens depends, among other things, on a genetic disposition.

In addition, the resulting sulfur-containing degradation products in the urine are perceived with different intensity by everyone and there are people who cannot perceive the smell at all due to an individual loss of smell.

If you belong to a group of people who cannot perceive the smell or only to a very small extent, don’t worry. You are in very good company with many great personalities. For example, Winston Churchill, Julius Caesar, and Napoleon Bonaparte are said not to have been able to perceive the typical asparagus urine smell .

Now you know where the smell in the urine after eating asparagus really comes from. The next time someone tells you that it’s all in your head, you can confidently answer that it is not! This is the end of the post. Thanks for reading!


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