Eat too much asparagus at dinner, and later, when you pee, you might notice an odd, vaguely cabbage-y aroma—or maybe you won’t. Asparagus is one of a handful of foods that, in some people, makes their urine smell weird and funky.
People have been noticing asparagus’ effect on our excretions for years. Benjamin Franklin wrote that “a few stems of asparagus eaten shall give our urine a disagreeable odor” — it’s one of his less-often cited quotes—while French novelist Marcel Proust was more of a fan. He said that asparagus “as in a Shakespeare fairy-story transforms my chamber-pot into a flask of perfume.”
Both Franklin and Proust fall into the group of people who produce smelly pee when they eat asparagus, and can also smell the said smelly pee they produce. In all, there are four types of people:
- those who produce smelly pee and can smell it
- those who produce smelly pee but can’t smell it
- those who don’t produce smelly pee but can smell it when someone else produces it
- those who can do neither
If you’ve never thought your pee smelled funny after eating asparagus, then either your pee genuinely didn’t smell funny because you don’t produce odorous urine—or it did, and you just aren’t able to detect it.
What percentage of people fall into each group is unclear. Various studies place the number of people who produce asparagus-effected urine at somewhere between a little under half and almost everybody, which is quite a wide range. Similarly, different studies have found as few as 10% of people or as much as 94% of people can smell asparagus pee. The effect is real— it’s just not clear as to how widespread it is. I won’t suggest ways you can work out which group you fall into, other than to note asparagus is cheap at your local grocery store, and you probably have small glasses at home that you could use as test tubes.
So, asparagus makes some people’s pee smell funny—including mine, and maybe yours. What’s going on? Science’s best guess is that asparagusic acid, a substance in asparagus, gets metabolized and broken down by some of our bodies into methanethiol, dimethyl sulfide, and a couple of other smelly volatile compounds. Scientists have been able to detect these compounds in some people’s urine but not others, which explains why some people’s pee smells and others don’t, although nobody knows why it’s the case.
Asparagus isn’t the only food that can make your pee smell funny, though it’s by far the most famous one. Personally, mine gets a weird musk if I eat too many bowls of Sugar Puffs for breakfast. Other foods that can potentially make your pee smell are alcohol, bananas, broccoli, Brussels sprouts, cauliflower, chicken, cilantro, coffee, cumin, fish, garlic, pineapple, turkey, and salmon.
Does any food make your pee smell weird? Let us know in the comments.