Hey there, fellow health explorers! Let’s talk about a universal human experience – one that’s equal parts weird, scientific, and slightly embarrassing. Have you ever enjoyed a delicious plate of asparagus, only to visit the bathroom later and wonder, What the heck just died in here?
Yep, I’m talking about asparagus pee. Not everyone smells this. But it’s that sulfuric, skunky aroma that hits you like a brick wall moments after you eat this otherwise innocent vegetable. But here’s the fun part—not everyone notices it. Is it your body? Your nose? Your destiny? The answer, my friends, is hidden in your genes.
Speaking of genes, there are other weird things that can happen in your body because of genetics, like I’m thinking of the snatiation gene which causes you to sneeze if you eat, or if you eat too much. READ MORE HERE.
Meet the Culprit: Asparagusic Acid
Asparagus isn’t just a tasty green spear, it’s a biochemical magician. It contains a unique compound called asparagusic acid, a sulfur-based molecule that gets metabolized into volatile compounds like methanethiol, dimethyl sulfide, and dimethyl sulfone. More on its health benefits down below.
Let me comment about the word “volatile” you see this term in research papers all the time and I just mentioned it above. I do not mean “volatile” as in explosive urine! 😂 In this context, when I talk about volatile sulfur compounds in asparagus pee (like methanethiol and dimethyl sulfide), I just mean they quickly turn into airborne molecules (gases) which is why people can smell the aftereffects of asparagus almost immediately after urinating!
Now, if you’re wondering where else you’ve smelled something similar, think of rotten eggs and skunks. It’s like asparagus is playing an olfactory prank on you!
Once you eat it, these sulfur compounds enter your bloodstream, hit your kidneys, and make a grand exit through your urine within 15 to 30 minutes. Talk about efficiency! But here’s where the genetic fun begins – not everyone perceives the stench.
The Smell Test: Producers vs. Perceivers
Research shows that about 90-95% of us produce these stinky sulfur compounds after eating asparagus. So if you think you’re special and immune to asparagus pee, well… chances are, you’re just nose-blind to it. You just can’t smell it, but most everyone else does if they go into the bathroom right after you.
A 2016 STUDY in The British Medical Journal reviewed 6,909 people’s DNA and found that while most of us are excreting asparagus funk, only half (about 50-60% of people) can actually smell it! The deciding factor? A handful of genetic variants on Chromosome 1 impact olfactory receptors, the smell detector proteins in your nasal tissue.
The Science Behind Asparagus Anosmia
Your ability to smell asparagus pee depends on genes in the OR2 family—olfactory receptors specialized for detecting sulfur-based odors. One big player is OR2M7, which sits on Chromosome 1 and plays a key role in sensing these smells.
If you carry certain single nucleotide polymorphisms (SNPs) (like rs13373863 or rs6689553 in case you have your gene report) your nose just ignores the stinky party happening in your urine. Scientists call this phenomenon “asparagus anosmia,” which sounds like a rare disorder but is really just nature’s way of keeping dinner parties civilized lol.
So next time someone swears their pee smells fine, they might not be lying, they just have genes that block out the funk. Speaking of lying or not lying, there is a thing called confabulation. I wrote a whole blog about it because some people actually believe the ‘lies’ they tell. Read this blog: The Truth About Confabulation: 10 Causes of ‘Honest Lying’ and Its Social Impacts.
Are You a Non-Producer? Maybe, But Unlikely
While just 5 or maybe even up to 8% of the population claim their urine doesn’t smell at all after eating asparagus, scientists aren’t entirely sure if that’s due to genetics, enzyme deficiencies, or just an exceptionally speedy metabolism.
It’s possible that some folks don’t break down asparagusic acid the same way, but the vast majority of “non-smellers” are really just “non-perceivers.” Translation? You’re probably still producing asparagus pee stink… you just don’t have the nasal receptors to confirm it.
Beyond Asparagus: Other Foods That Impact Urine Odor
Asparagus isn’t the only food that can make your bathroom break interesting. Here are some other culprits:
- Garlic & Onions – More sulfur shenanigans! These contain allyl methyl sulfide, which can make your pee (and sweat) smell garlicky. If you are bold and want more sulfur in your life, try my recipe for Garlic Parmesan MUSTARD GREENS.
- Coffee – That bitter, acidic brew contains polyphenols, which can give urine an earthy, almost burnt-coffee scent—especially if you’re dehydrated. Coffee actually has some medicinal benefits, read my other article: Coffee Has A Unique Impact on Weight, Mood and Cancer. You may also enjoy this interesting comparison/contrast: Matcha vs. Coffee: Unlocking the Power of Caffeine for Health and Well-being.
- Fish – Some people lack the enzyme flavin monooxygenase 3 (FMO3), which leads to trimethylamine buildup, which makes urine smell a little fishy.
- Brussels Sprouts & Cabbage – Like asparagus, these are rich in sulfur compounds, but the effect is usually milder.
Asparagus and Health: More Than Just Funky Pee?
Asparagusic acid, the sulfur-containing compound in asparagus responsible for the infamous “asparagus pee” smell, hasn’t been extensively studied for direct medicinal benefits. However, its sulfur-based metabolites may contribute to some health-promoting effects. Here’s what I can tell you about the potential health benefits found in asparagus:
- Detoxification Support
Asparagus is rich in compounds that create glutathione, a powerful antioxidant that plays a key role in detoxification, especially in the liver. Similarly to the peroxide-removing antioxidant CATALASE this comopound breaks down a lot of free radicals.
Sulfur-containing compounds help regenerate and support glutathione synthesis, which aids in neutralizing free radicals and detoxifying heavy metals.
I can’t get passed this section without mentioning my tasty superfood drink mix for detoxification, check out YUMMY GREENS if you like those. Actually, check out that supplement if you DON’T like those because mine tastes delicious, and I will guarantee that with a 100% money back guarantee! This formula is patented! We rarely ever get returns, people love it!!! It used to be called Thyroid Greens, because it’s safe for your thyroid gland unlike most other formulas, but I changed the name. And NO it will not make smelly urine because it is free of asparagus, it contains dulse and sea lettuce instead.
- Anti-Inflammatory & Antioxidant Properties
Sulfur compounds have been linked to reduced oxidative stress and inflammation.
Similar to sulfur-rich vegetables like garlic and broccoli, asparagus may help lower chronic inflammation markers.
- Potential Antimicrobial Effects
Some sulfur metabolites, including those in garlic and onions, have been shown to inhibit bacterial growth.
While asparagusic acid itself hasn’t been studied for antimicrobial effects, related sulfur compounds often exhibit antibacterial and antifungal properties.
- Support for Joint & Connective Tissue Health
Sulfur is a crucial element in forming collagen, keratin, and cartilage, which support skin, hair, and joint health.
Some researchers speculate that sulfur-containing vegetables may contribute to joint flexibility and pain relief (though studies are limited).
- Possible Cancer Protective Effects
Sulfur compounds found in cruciferous vegetables (like sulforaphane in broccoli) have been linked to cancer prevention by inducing apoptosis (cell death) in cancer cells.
Asparagus also contains asparagine, an amino acid involved in cell metabolism, which some research suggests may play a role in cancer growth regulation.
NAC, MSM and L-Cysteine: Sulfur Supplements that Smell… and Heal?
A lot of you take supplements to promote glutathione production or to improve lung function. Things such as NAC or L-cysteine (which is in my Immune Script®) are precursors to glutathione, one of the body’s most powerful antioxidants. And they contain sulfur (not sulfa, that’s totally different).
Then there’s MSM (methylsulfonylmethane) which is also a sulfur donor, but it doesn’t help you make glutathione like NAC and cysteine. MSM itself is naturally found in plants, animals and humans. And you can buy supplements of it too.
MSM is taken by many people for it’s ability to help with collagen formation, joint health and inflammation reduction. It’s in my Joint Script® for that reason. Anway, it breaks down into dimethyl sulfone and sulfur dioxide, which are less odorous than NAC’s hydrogen sulfide (H₂S). Taking supplements with MSM can *maaaaybe* affect your sweat or breath, but it will rarely affect urine odor the way that NAC or cysteine does. Still, I want to mention it here for completeness since it’s a sulfur donor. If MSM interests you, here’s a BLOG about my trip to a hot spring with sulfur in it.
Anyway, these sulfur-based supplements can contribute to changes in body odor, but not in the same way as asparagus.
- Why Asparagus Pee Smells Different:
- Asparagusic acid is unique to asparagus and breaks down into volatile sulfur compounds like methanethiol and dimethyl sulfide, the main culprits behind the skunky urine smell.
- This happens rapidly, within 15-30 minutes, making the effect highly noticeable.
- Why NAC and L-Cysteine Don’t Have the Same Effect as Asparagus:
- NAC and L-cysteine are broken down into hydrogen sulfide (H₂S) and other sulfur metabolites, which can contribute to a rotten egg-like smell, but this usually affects breath, sweat, and gas more than urine.
- If taken in high doses (600 – 1,200mg per day), NAC can sometimes cause a slight sulfuric smell in urine, but it’s milder than asparagus pee.
- Since NAC is metabolized slowly in the liver, rather than producing urine metabolites like asparagusic acid, it doesn’t cause that immediate, pungent urinary effect. If you have poor liver function, or sluggish pathways there, the sulfur metabolites might linger longer, increasing body odor.
- If your gut bacteria are out of balance, meaning you have poor probiotic status, then sulfur metabolism will produce more hydrogen sulfide, leading to gassy, eggy smells.
So, Should You Worry?
If you take NAC or L-Cysteine and notice an increase in sulfuric body odor, it’s usually a sign of detoxification – not necessarily a bad thing! However, if it’s overwhelming, you can:
✔ Support liver detox with molybdenum and B vitamins (especially B6, B9, B12)
✔ Stay hydrated to flush out excess sulfur metabolites
✔ Consider adjusting the dose if the smell becomes bothersome
NAC and L-cysteine won’t make your urine smell like asparagus, but they can contribute to mild sulfuric odors, usually in sweat or breath rather than pee. If your urine starts smelling strongly of sulfur on NAC, it’s worth checking liver function, gut health, and hydration levels to see what’s going on under the hood!
Summary
Your DNA holds the key to whether you’ll smell that signature odor. If you can’t detect it, congratulations, you win the genetic lottery of blissful ignorance. If you can smell it, at least you know your smell receptors are in mint condition!
Want to test your genetics at home without a 23andme or similar genetic test? You totally can! Eat some asparagus, wait a short while (maybe 30 minutes or an hour) go to the bathroom to pee, and take a whiff. Are you Team Smeller or Team Oblivious?
Either way, your body is doing something pretty interesting, at no extra charge!
Got any questions about other weird food effects? Wondering if you have the gene for cilantro tasting like soap?! That’s a thing. Drop me a line at scriptessentials@gmail.com so I can research it for you – remember I live for this stuff!
Suzy Cohen, has been a licensed pharmacist for over 30 years and believes the best approach to chronic illness is a combination of natural medicine and conventional. She founded her own dietary supplement company specializing in custom-formulas, some of which have patents. With a special focus on functional medicine, thyroid health and drug nutrient depletion, Suzy is the author of several related books including Thyroid Healthy, Drug Muggers, Diabetes Without Drugs, and a nationally syndicated column.
