Somewhere along the way, kale went from being the leafy decoration nobody ate at the salad bar to becoming the darling of the health-food world. Some people love it, while others are still wondering how something that tastes like lawn clippings became a nutritional celebrity. Suddenly, it was everywhere. Kale salads, kale smoothies, kale chips, kale powders, and probably a kale-scented candle for people who wanted their entire house to smell like nutritional superiority.
And to be fair, kale earned quite a bit of that attention. This sturdy, sometimes annoyingly chewy green packs an impressive amount of nutrition into its leaves. It’s also a member of the cruciferous vegetable family, alongside broccoli, cauliflower, cabbage, and Brussels sprouts. Apparently, nutritional overachievement runs in the family.
But before we crown kale the undisputed queen of vegetables, there are a few things worth knowing. Like many healthy foods, kale comes with some considerations, including its effects on thyroid function, digestion, and certain medications. And yes, we’ll talk about oxalates, because even vegetables have baggage.
What’s Actually Inside Those Leaves?
Kale has an impressive nutritional résumé. And unlike some foods that need a marketing department to convince us they’re healthy, kale has the nutritional credentials to back up its reputation.
Let’s start with vitamin K, because kale has plenty of it. This nutrient helps your blood clot normally and supports bone health, which becomes especially important for women navigating menopause, when declining estrogen can accelerate bone loss. Unfortunately, eating kale doesn’t mean you can cancel your strength workouts. Nice try.
Then there’s vitamin C, which most of us associate with oranges. Kale happens to be an excellent source, supporting immune function, collagen production, and the body’s ability to absorb iron from plant foods. Collagen helps maintain our skin, blood vessels, and connective tissues, so vitamin C has considerably more responsibility than simply helping us through cold season.
Your eyes get some attention, too. Kale contains beta-carotene, which the body can convert into vitamin A, along with lutein and zeaxanthin, two plant compounds that support retinal health. Considering how much time we spend staring at screens, our eyes could probably use the nutritional assistance.
And let’s not forget calcium, potassium, and magnesium, which support everything from bone strength and muscle function to nerve communication and healthy blood pressure. Interestingly, our bodies can absorb calcium from kale relatively well compared with calcium from spinach. Apparently, kale isn’t content with simply having nutrients; it wants us to actually use them.
Finally, there’s fiber, which supports regular bowel movements and helps nourish the beneficial bacteria living in our intestines. Of course, those bacteria can also produce some rather noticeable side effects when we suddenly feed them more fiber than they’re accustomed to. We’ll get to that shortly.
Kale’s Secret Weapons: Antioxidants and Plant Compounds
Beyond its vitamins and minerals, kale contains glucosinolates, naturally occurring compounds found in cruciferous vegetables. When kale is chopped or chewed, these compounds can be converted into substances researchers are studying for their potential roles in cellular protection and the body’s natural detoxification processes. Kale also contains antioxidants such as quercetin and kaempferol, which are being investigated for their potential benefits in protecting cells from oxidative damage.
Does that mean kale prevents cancer, eliminates inflammation, or magically detoxifies your liver? No. Your liver already has an impressive detoxification system, and kale isn’t showing up with a mop and bucket to clean it out. But the nutrients and plant compounds in kale can support the body’s normal functions, which is considerably more useful than the exaggerated promises often attached to superfoods.
Now for the Fine Print: Kale Has a Few Issues
I love whole foods, but I don’t believe any food deserves a free pass simply because it grew out of the ground. Kale is a wonderful example of why understanding our food is more valuable than blindly following the latest superfood trend.
Oxalates: Kale Is Mostly Innocent
Oxalates are naturally occurring compounds found in many plant foods. In susceptible individuals, excessive oxalate exposure can contribute to calcium oxalate kidney stones. But here’s the interesting part: kale is generally considered a low-oxalate leafy green, especially compared with spinach and Swiss chard.
That’s right. Kale gets dragged into the oxalate conversation simply because it’s green and leafy, while spinach is over there quietly carrying a much larger oxalate load. Apparently, vegetables are guilty by association now.
Oxalates are a subject I’ve explored extensively because of my own experience with calcium oxalate kidney stones. If you’d like to learn more about oxalates, why they matter, and how they can affect your health, read my article, How Can Good-for-You Foods Be Bad? Secrets of Oxalates. I’ve also created a free Oxalates Food Guide identifying high-, medium-, and low-oxalate foods to help you make more informed choices.
Goitrogens: Is Kale Messing With Your Thyroid?
Kale contains naturally occurring compounds called goitrogens, which can interfere with the thyroid’s ability to use iodine under certain circumstances. Since iodine is essential for producing thyroid hormones, this has understandably raised concerns about eating cruciferous vegetables.
But before you start treating your kale salad like a thyroid assassin, consider the circumstances. For most people with adequate iodine intake, eating normal amounts of kale isn’t a significant concern. Problems are more likely with iodine deficiency or unusually large quantities of raw cruciferous vegetables. Cooking also reduces some of the compounds responsible for these effects, making steamed or sautéed kale a good option.
Vitamin K and Blood Thinners
Remember all that wonderful vitamin K supporting your bones? Well, it also plays an important role in blood clotting, which means people taking warfarin need to pay attention to how much they’re consuming. That doesn’t mean kale is off the menu, but keeping vitamin K intake reasonably consistent matters because sudden changes can interfere with the medication’s effectiveness. Not all blood thinners interact with vitamin K, so knowing which medication you’re taking matters.
Bloating, Gas, and Digestive Drama
Kale’s fiber is wonderful for the gut microbiome, but it can also contribute to bloating and gas, particularly when eaten raw or in large amounts. The bacteria in your intestines ferment certain carbohydrates, producing gas in the process. Sometimes the resulting digestive orchestra is considerably louder than anyone anticipated.
If a giant kale salad leaves you feeling like someone inflated a balloon in your abdomen, don’t immediately write kale off. If your body isn’t accustomed to that much fiber, start with smaller portions and gradually increase them, giving your gut microbiome and digestive system time to adapt. Light steaming or sautéing can also make kale easier to digest. There’s no nutritional award for forcing down a mountain of raw kale while your digestive system stages a protest, especially when a little patience may be all that’s needed.
Pesticides: Another Reason to Pay Attention
Kale’s leafy surface can retain pesticide residues, which is one reason I prefer buying organic whenever possible. But organic doesn’t automatically mean free of all contamination, so washing your kale thoroughly under running water is still important. Leafy greens can also carry harmful bacteria regardless of how they’re grown, so proper handling and storage matter, too. Even a vegetable with a glowing nutritional résumé still needs basic hygiene.
Raw, Steamed, Sautéed, or Massaged?
My relationship with kale goes back long before anyone started calling it a superfood. One of the dishes I remember eating as a child was my grandmother’s kale soup with linguiça, a Portuguese sausage. I don’t eat linguiça these days, but I’ve made plenty of my own soups and dishes featuring kale, and whenever I do, I think of my grandmother. It’s funny how a simple ingredient can bring back memories of someone and the food they made for us, even decades later.
This past season, I grew kale in my own garden, and what a difference that made! Fresh kale picked right off the stalk in your own backyard is unlike anything you buy at the grocery store. It was surprisingly tender, a little sweet, pesticide free, and absolutely delicious. And it was incredibly easy to grow. The hardest part was figuring out how to harvest the leaves without cutting off the plant’s ability to keep producing. Once I learned to trim the lower outer leaves and leave the center growing, that kale just kept giving throughout the season. It’s definitely earned a spot in next year’s garden.
These days, I enjoy kale in all kinds of dishes, from soups and curries to salads, and pesto. I’ve even been working on a zucchini lasagna with a layer of kale tucked inside. Want to put all that kale nutrition to work in your kitchen? Try my Cauliflower Curry, Healthy Eats Vegetable Soup, or Ultimate Kale Pesto.
Preparation also influences kale’s nutritional benefits. Raw kale preserves more heat-sensitive vitamin C, while cooking softens its leaves and reduces some goitrogen-related activity. Adding a little healthy fat, such as extra-virgin olive oil or avocado, helps the body absorb kale’s fat-soluble carotenoids. And if you’ve ever tried chewing through a raw kale salad that felt suspiciously like landscaping material, try massaging the leaves with olive oil and lemon juice. Apparently, even kale appreciates a good massage.
So, Does Kale Deserve Its Superfood Reputation?
Absolutely. But that doesn’t mean it needs to be the only leafy green on your plate. Broccoli, cabbage, arugula, collard greens, and plenty of other vegetables offer their own nutritional benefits. Variety gives us access to a broader range of nutrients and plant compounds, and it makes eating healthier a lot more interesting.
One of the central messages in my book, The Awakened Body, is that learning to listen to your body changes your relationship with food. My own journey taught me that eating healthier isn’t simply about following a list of good foods and bad foods. It’s about understanding what we’re eating, noticing how our bodies respond, and making more informed choices. So enjoy your kale however you like it, but remember that even the healthiest foods deserve a little curiosity. And while eating an entire field of kale won’t make you immortal, judging by the amount of chewing involved, it might feel like you’ve been eating for an eternity.