6 myths you may have heard about kale
The past few years have seen kale rise to star status at farmers' markets and grocery stores. But with great popularity comes major confusion: Is kale actually the greatest leafy green on Earth? Can kale help you lose weight? Or—hold up—might kale actually be harmful to health? Read on as we delve into the claims surrounding this buzzy salad staple and stack them up to the science. Spoiler alert: We have only good things to say!
MYTH: The kale trend is total hype.
FACT: Feel free to skip the trendy “Kale yeah!” T-shirt if it’s not your vibe. Just know the veggie’s nutrition stats are no passing fad. Two cups of kale—about the amount you’d enjoy in a salad—deliver almost all your vitamin A for the day (99% Daily Value from beta-carotene), along with 67% of your vitamin C. You’ll also get 2 g of fiber and protein (about how much you can expect from most veggies), plus smaller yet significant amounts of vitamin B6, calcium, potassium, and magnesium.
While no single food can make or break your health, kale is a standout pick to put on your plate. As part of an overall healthy pattern of eating, research has linked the cruciferous veggie and/or its nutrients to a number of potential health benefits:
- Reduced disease risk: Kale is rich in antioxidants that help protect cells from oxidative stress and DNA damage, two processes that can increase one’s risk of developing heart disease and type 2 diabetes. Another potential benefit: High consumption of brassica vegetables—a family that includes broccoli and cauliflower alongside kale—was correlated with a decreased incidence of some cancers in a landmark research review published in Cancer Epidemiology, Biomarkers & Prevention.
- Blood pressure regulation: Eating foods that contain potassium, calcium, and magnesium may improve blood pressure levels, studies have shown. While more investigation is needed to pinpoint the effects of kale specifically, many health experts advise eating a diet high in those minerals to help reduce the risk of hypertension.
- Vision protection: Leafy greens such as kale are rich in lutein and zeaxanthin, two nutrients linked to a lower risk of age-related macular degeneration and cataracts, according to a 2013 review in Nutrients. The duo also helps protect ocular tissues from sun damage. And once consumed, kale’s motherlode of beta-carotene converts to vitamin A, which plays a key role in corneal health.
- Better bone health: Kale is a potent source of bone-building vitamin K—2 cups of leafy goodness deliver 293% of your daily recommended intake of this underconsumed nutrient. One large-scale study of women found that adequate vitamin K intake was associated with a reduced risk of hip fracture. And not to be overlooked: 2 cups of kale also contain 6% of the recommended daily value of calcium, another nutrient needed for strong bones.
MYTH: Eating kale every day is dangerous.
FACT: The rumor that kale is harmful to health went viral in 2015 and has been kicking around the Internet ever since. It got started when a self-described vitality researcher in California publicized claims that kale soaks up toxic levels of lead, arsenic, and thallium from soil as it grows, reportedly leading to problems with cognition and other functions for people who eat kale regularly. Though some soil does contain trace amounts of heavy metals and other substances that could be harmful to humans in high amounts, the claims about kale toxicity have never been published in a peer-reviewed journal and are not considered scientifically valid. Just for reference, one study in the Journal of the North Carolina Academy of Science found that a typical adult could chow down on 153 pounds of kale daily and still be under the safe limit of lead exposure set by the World Health Organization.
Given that less than 10% of U.S. adults eat the five servings of fruits and veggies a day recommended by public health experts, you probably don’t have to worry about “dangerous” levels of kale. Just one caveat: If you are on a blood-thinning medication, check with your doctor before changing your kale intake. The leafy green’s high levels of vitamin K could interfere with the medication’s effectiveness, which might necessitate a dosage adjustment.
MYTH: Kale is healthier than spinach.
FACT: Hey, there’s no question that kale is pretty great. But nutrition is not a contest, and a healthy diet includes a variety of plant-based foods. Both kale and spinach are low in calories, provide antioxidant benefits, and deliver a unique mix of nutrients. Spinach is slightly higher in magnesium, iron, and folate, which are important for circulation, muscle function, and cognition. Meanwhile, kale delivers much more vitamin C and is a touch higher in calcium and protein. In the end, there’s no reason to pit leafy greens against each other! From spinach and kale to arugula and chard, they all support good health in their own wonderful ways.
MYTH: Kale will help you lose weight.
FACT: Whether celery juice or the alkaline diet, it seems we’re always hearing about some “wellness” trend promising fast and easy weight loss. The truth is, there’s no quick fix. Like other leafy greens, kale is low in calories for its volume (25 calories per 2-cup serving). And for WW members, it’s a ZeroPoint™ food across myWW+ plans, so you can add it to meals and snacks without worrying about tracking. So, yes: Eating more fruits and vegetables can indeed help with weight management. That said, kale doesn’t have any special ability to boost metabolism or melt pounds. Lasting weight loss generally involves multiple aspects of a person’s lifestyle, including physical activity and healthy patterns of eating.
Related: What to eat when you’re out of SmartPoints®
MYTH: The best way to boost your kale intake is through juices.
FACT: Sure, juicing may seem like a quick and easy way to consume more kale, especially if you don’t love the slightly bitter taste of its leaves. Just know that from a nutritional standpoint, sipping juice isn't quite the same as adding kale to your diet. The juicing process omits the veggie’s pulp—and with it, most of the fiber. Fiber plays a role in helping you feel full after a meal, and research shows that liquids in general don’t promote the same feeling of fullness as solid foods do.
Related: Should you try a juice cleanse?
If you’re really craving kale in liquid form, consider making a smoothie instead. The blending process retains the pulp, so you’ll get more fiber than you would with a squeezed juice. Grabbing a commercially bottled kale drink on the go? Check the Nutrition Facts label and opt for a brand with zero grams of added sugar per serving, limited additives, and at least 100% of the Daily Value for vitamins A and C. While you won’t reap the full satiating benefits of whole kale, you might still get some nutritional perks.
MYTH: Raw kale is better for you than cooked.
FACT: Proponents of raw food diets would have you believe that basically all uncooked foods are superior to their cooked versions. This eating style has surged in popularity over the past few years, thanks in part to social media influencers waxing poetic over pretty pics of raw, rainbow-color fruits and veggies.
While research suggests that the heat of cooking can zap some of kale’s antioxidants, flavonoids, and minerals, that doesn’t mean cooked kale is bad—or that raw kale is best for you. For starters, cooked kale is plenty nutritious, retaining its fiber, beta-carotene, and protein. Moreover, eating foods you actually enjoy is important. If you prefer your kale sautéed in a stir-fry vs. shredded raw into a salad, so be it. (Check out these 21 raw and cooked kale recipes for some delicious inspo.) In general, the immense benefits of consuming plants in any form—cooked or raw—outweigh the relatively minor nutrition penalties of cooking.
Jaclyn London, MS, RD, CDN is a registered dietitian (RD) and certified dietitian nutritionist (CDN), and holds a bachelor of arts degree from Northwestern University and a master of science degree in clinical nutrition from New York University. WW’s head of nutrition and wellness, London is also the author of Dressing on the Side (and Other Diet Myths Debunked): 11 Science-Based Ways to Eat More, Stress Less, and Feel Great About Your Body, and previously served as Good Housekeeping’s nutrition director.
Nicole Saporita is a senior content manager for consumer wellness at WW. A writer, editor, and content strategist based in New York, she specializes in health & wellness, lifestyle, consumer products, and more. Her work has appeared in Good Housekeeping, Prevention, and REDBOOK magazines.
This article was reviewed for accuracy in July 2021 by Tiffany Bullard, PhD, manager for clinical research at WW. The WW Science Team is a dedicated group of experts who ensure all our solutions are rooted in the best possible research.