by Ocean Robbins: Asparagus may be a weird-looking vegetable that makes your pee smell funny, but it’s also a nutritional powerhouse and a culinary giant.
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What’s in asparagus that’s so good for you, and what health benefits does it provide? How do you select the best spears, and how do you store them for maximum flavor and nutrition? Find out below!
If there was an Academy Award ceremony for produce, I’d argue that asparagus should be a perennial contender for “Healthiest Vegetable.” And we’ll see why in a little bit. But first, we have to deal with the smelly elephant in the room. Because the Oscar for “Vegetable that Causes the Funniest-Smelling Pee” goes, yet again, to asparagus. (Polite applause, followed by Asparagus, embarrassed, mumbling an acceptance speech and quickly slinking off the stage.)
OK, let me try to be mature about this weird feature of asparagus because it’s very much related to asparagus’ health benefits. When you eat asparagus, one of the compounds that your body metabolizes is called asparagusic acid. (I give whoever named it an A for accuracy and a C for creativity.)
Inside your body, asparagusic acid turns into several different by-products, one of which is called methanethiol. This substance is what gives post-asparagus urine its distinct odor. Now, not everyone experiences aromatic pee. Some people may produce far more methanethiol than others, due to genetic differences in their metabolism. And some (lucky? unlucky?) folks simply lack the olfactory ability to detect the odor, and so may wrongly believe that they don’t produce it or that it doesn’t even exist.
Although the smell is not everyone’s cup of tea (if it is your cup of tea, I may decline an invitation to your tea party), the compounds responsible for it are part of what makes asparagus so healthy.
In this article, we’ll look at some of the ways asparagus can support your health. We’ll explore its nutritional profile, check out the research on asparagus health benefits, and share how to choose and store asparagus to maintain its health benefits. Plus, if you stay all the way to the end, you’ll find a link to our companion article with seven delicious asparagus recipes.
On paper, asparagus is a nutritional powerhouse. Calorically speaking, it’s mostly carbohydrates with a small but not insignificant amount of protein: 2.4 grams of protein per 100-gram serving of asparagus. That same serving also delivers two grams of fiber, which sounds a bit low since asparagus is sometimes extremely chewy (especially if you don’t cook it or neglect to cut off the tough, fibrous stems).
Asparagus is also an excellent source of both fat-soluble and water-soluble vitamins, especially vitamins A, C, E, K, and most of the B vitamins. Plus, it’s no slouch when it comes to minerals, including copper, manganese, selenium, and potassium. Most of the nutrients in asparagus increase slightly in concentration when it’s cooked rather than eaten raw, although you can get a heap of benefits either way.
Asparagus also delivers “specialty nutrients” that pack huge nutritional punches, including potent antioxidants like lutein and zeaxanthin, which are important to eye health; glutathione, which is a multi-disease-fighting powerhouse; and quercetin, which has anti-inflammatory properties.
And, as we’ve seen (or smelled), asparagus also contains the sulfur-containing compound asparagusic acid that makes your pee smell weird. While the smell of sulfur may conjure mental images of fire and brimstone, its presence in vegetables generally signals nutritional superpowers. Other veggies high in sulfur include allium (such as onions and garlic) and cruciferous (such as cabbage, broccoli, and kale) vegetables, two of the top superfood categories.
These sulfur-rich foods play a significant role in preventing various diseases, including chronic inflammation, cancer, diabetes, obesity, and neural dysfunction. They’re also being studied for their ability to enhance the effects of chemotherapy and support neurological function.
And we’re just scratching the surface in understanding asparagus’ rich cocktail of phytonutrients and their ability to promote health and fight disease across a wide spectrum of organs, systems, and conditions. Purple asparagus, in particular, deserves a Lifetime Achievement Award for its high concentrations of anthocyanins.
Top 6 Health Benefits of Asparagus
While there’s much yet to discover about how asparagus can help us thrive, there are six areas, in particular, where research is beginning to make serious inroads: gut health, cancer treatment, cardiac health, liver and kidney function, eye health, and skin health (aka antiaging).
You’ll notice that much of this research is in its early stages, which unfortunately means researchers are often testing extracted compounds on rodents rather than simply feeding asparagus to humans and seeing what happens. (Our view on the use of animals in medical research is here.)
That said, there’s good reason to expect that at least some of the health benefits transfer across species — especially since whole foods typically deliver more nutritional benefits than individual nutrients extracted from those foods.
Asparagus and Gut Health
In 2020, researchers from China fed asparagus extracts to mice who had been on a high-fat diet and discovered that the compounds found in asparagus increased the diversity of the rodents’ gut bacteria in ways that could theoretically treat the elevated cholesterol caused by their diet. A comparison group received cholesterol-lowering medication instead of asparagus and didn’t show the same increase in gut biodiversity.
The following year, another Chinese research lab showed that the fiber from asparagus not only altered the ratios of gut bacteria in mice who had been on a high-fat diet but also lowered total cholesterol, LDL cholesterol, and triglycerides in the serum of mice who had been on a high-fat diet.
Expanding on those previous studies, researchers from Spain also looked for the specific compounds in asparagus that enable it to so significantly improve microbial diversity. And they flagged several, including xylose, inulin, flavonoids, and saponins, for future study.
Asparagus and Cancer
One promising avenue for the treatment of cancer is the search for metabolic interventions that starve cancer cells but leave healthy cells unharmed. A compound in asparagus, asparagine, appears to do just that to leukemia cells. And scientists are looking for ways to harness this power in the fight against other cancers.
A 2021 study by an international group of researchers showed that asparagus slowed ovarian cancer progression in mice, both fighting the growth of tumors and preventing their metastasis into other organs and parts of their bodies.
And in the same year, a team of Italian scientists also found that asparagus compounds given in conjunction with chemotherapy for breast cancer improved the specificity of the treatment. That is, asparagus appears to allow the chemotherapeutic agents to target cancer cells more specifically and effectively, and leave healthy cells alone.
Asparagus and Heart Health
The gut bacteria changes that asparagus can bring about appear to favor heart health by lowering levels of circulating fats in the blood, at least in test-tube studies.
Food scientists in Japan discovered in 2013 that asparagus extract lowered blood pressure in hypertensive mice. In a randomized controlled trial, the extract dropped the average mouse’s systolic blood pressure significantly (to 160, a full 30 points lower than the control group), and appeared to do so via the same mechanism as a major class of hypertensive drugs, the ACE inhibitors.
As a result, there’s hope that asparagus compounds (or even raw or cooked asparagus!) could help people reduce their hypertension without the side effects of these drugs.
Asparagus and Liver and Kidney Disease
Asparagus is also a possible friend to your liver and kidneys. A 2015 study out of China identified a bunch of compounds in asparagus that appear to be protective against chemical changes associated with liver scarring (the process that leads to cirrhosis) in test-tube samples.
In 2018, an Iranian team extended this line of inquiry, this time with a controlled study of live mice. They found that asparagus extract protected against oxidative stress as well as liver and kidney damage in mice who were exposed to the endocrine disruptor BPA.
Asparagus and Eye Health
Many of the compounds in food that can help prevent eye-related disorders, including macular degeneration, are in asparagus. Purple asparagus, in particular, appears ready to walk the eye-health red carpet, thanks to its high concentration of anthocyanins.
In a 2020 study, an Iranian research team showed that asparagus extract helped to prevent cataract formation in baby rats.
Asparagus and Skin Health
One of the chemicals in your body that protects your skin from ultraviolet (UV) radiation damage is called Heat Shock Protein 70 (HSP70), which sounds like an expensive shampoo that was named by a 1950s doo-wop band.
But in 2018, Japanese researchers took normal human dermal fibroblasts (the cells that repair damaged skin) and exposed them to UV-B radiation in test tubes. Researchers added asparagus stem extract to some tubes, while others served as controls. After 24 hours, the tubes with asparagus extract contained significantly more HSP70, suggesting that the vegetable was able to protect the fibroblasts from radiation damage.
And a 2021 study out of Thailand also investigated the effects of asparagus on wrinkle development. Researchers tested different parts of the asparagus and found that the spear contained the most potent anti-wrinkle compounds. They concluded that asparagus could be an effective natural ingredient in anti-wrinkle products.
How to Choose Asparagus
Now that you’re thoroughly impressed with the comprehensive medicine cabinet that is asparagus, I hope you’re thinking about ways to incorporate this wonder veggie into your diet.
The first step is knowing how to select the best-tasting and most nutritious spears.
You can buy fresh asparagus when in season (late spring through summer) at many grocery stores and farmers markets. It’s one of the first spring vegetables to appear in many parts of the world.
You can also grow it yourself, with less effort than many other garden veggies. That’s because asparagus is a perennial. Plant it once, and within 2–3 years you’ll have feathery tips popping out of the garden bed every spring. All you’ve got to do is take care of the soil, weed out anything that isn’t asparagus, water if needed, remember where you planted them so you don’t rototill that bed by accident — and of course, harvest.
Whether you purchase asparagus or grow it yourself, fresh green asparagus spears should be bright green and firm, with tightly closed tips. The purple and green varieties should have vibrantly colored tips as well.
You’ll also want to avoid slimy or wilted stems. Give a little sniff (don’t worry, no one’s looking) to check that the stalks emit a clean, slightly sweet aroma (so unlike how they leave the body!).
How to Store Asparagus
Store your asparagus in the refrigerator until you’re ready to prepare it. For maximal freshness, you’ll want to keep the bottoms of the stems moist. And there are a couple of easy ways to do this, depending on how much vertical space you have in your fridge.
If there’s room, you can stand the green, purple, or white spears upright in a container with an inch or two of water in the bottom. One trick for getting more headroom is to trim the bottom inch or so of the stems, which also makes it easier for the asparagus to absorb water and stay fresh.
Alternatively, wrap the bottom of the stems in a damp paper towel and put them in a zip-top produce bag.
Don’t wash asparagus until you’re ready to use it because moisture will cause the tips to become mushy. In any case, try to use asparagus within a few days of purchase. Like many veggies, asparagus begins to lose nutrients as soon as it’s harvested.
If you have a bumper crop that you can’t eat all at once, or you accidentally buy 20 bunches at the store, you can also freeze asparagus spears for later use. Blanch them in boiling water for a couple of minutes, then plunge them into ice water, dry them, and freeze them in airtight bags or containers.
You can also pickle or can asparagus, but you will lose some nutritional value in the process.
Now — ready for that collection of amazing asparagus recipes? Here’s your link: How to Cook & Use Asparagus: 7 Simple and Tasty Recipe Ideas
Hooray for Asparagus’ Health Benefits!
Asparagus may be a weird-looking vegetable that makes your pee smell funny, but it’s so much more. In those pointy spears lies a nutritional powerhouse that provides a variety of health benefits, including supporting gut health, helping to fight cancer, protecting the heart, and promoting eye and skin health.
Asparagus is an excellent source of vitamins, minerals, and antioxidants, making it a valuable addition to any diet. And to get the most nutritional benefit, it’s important to choose and store asparagus correctly. With its unique flavor and numerous health benefits, asparagus is a versatile vegetable that will add value and color to your spring and summer menus.