The Exact Nutritional Benefits of Kale
Kale remains one of the most hyped-up foods in the health community. Dietitians, marketers, and recipe developers all claim kale is a nutritional powerhouse — but why? What exactly is in kale that makes the veggie so nutrient-rich?
To demystify the beloved leafy green, we’re going to break down its exact nutritional value. First, though, let’s address a common question: Is kale a superfood?
Is Kale a Superfood?
The definition of a superfood varies depending on the person you’re talking to. However, if you consider a superfood a nutrient-dense food that has proven health benefits, then kale definitely qualifies.
Kale Nutrition Facts
Like other dark leafy greens, kale is easy to eat in volume, especially if it’s cooked down to a more compact size. However, a standard serving is one cup of cooked kale or two cups of raw kale, says Jennifer Glockner, R.D.N., and creator of Smartee Plate.
Interestingly, when you cook kale, the value of some of the nutrients increases, while others decrease. Here’s how the nutritional value of kale shakes out:
One cup of cooked kale contains:
- 42 calories
- 3.47 grams of protein
- 6.25 grams of carbs
- 4.7 grams of fiber
- 177 milligrams of calcium
- 30 milligrams of magnesium
- 50 milligrams of phosphorus
- 170 milligrams of potassium
- 21 milligrams of vitamin C
- 77 micrograms of folate
- 172 micrograms of vitamin A
- 493.8 micrograms of vitamin K
By contrast, two cups of raw kale contain:
- 15 calories
- 1.23 grams of protein
- 1.86 grams of carbs
- 1.7 grams of fiber
- 107 milligrams of calcium
- 14 milligrams of magnesium
- 23 milligrams of phosphorus
- 146 milligrams of potassium
- 39 milligrams of vitamin C
- 26 micrograms of folate
- 101 micrograms of vitamin A
- 163.6 micrograms of vitamin K
Let’s review what some of the key vitamins, minerals, and nutrients in kale actually do for your body.
1. Vitamin C
“Vitamin C is an antioxidant that’s important for skin health, wound healing, and iron absorption,” says Newgent.
Vitamin C helps synthesize collagen, a protein that’s an essential part of your skin and connective tissue like tendons and ligaments. Plus, vitamin C has long been reported to help boost your immunity, says Glockner.
According to the 2015–2020 Dietary Guidelines for Americans, the recommended dietary allowance (RDA) for vitamin C is 75 to 90 milligrams a day for adults. One cup of cooked kale has 21 milligrams of vitamin C, which is nearly 30% of your daily intake.
Folate is a B-vitamin that helps make new cells in the body, Newgent says. “For pregnant women, it’s especially important for prevention of birth defects associated with the brain and spine,” she explains.
The RDA for folate varies by age, but most adults should aim to consume 400 micrograms a day. Anyone who is pregnant or breastfeeding should aim for 600 micrograms a day.
With 77 micrograms of folate, one cup of cooked kale provides almost 25% of your daily intake.
3. Vitamin K
Vitamin K is a fat-soluble vitamin that helps keep your tissues and bones healthy, says Newgent. If a vitamin is fat-soluble — as opposed to water-soluble — it means your body needs healthy fats to help absorb the vitamin properly. Once your body absorbs fat-soluble vitamins, it stores them in your liver and fatty tissues.
Vitamin K isn’t just good for your tissues and bones, though. It also helps prevent blood clotting, says Glockner.
The RDA for vitamin K for adults is 90 to 120 micrograms per day. One cup of cooked kale has almost 500 micrograms of vitamin K, whereas a cup of raw kale contains 82 micrograms.
“Kale is packed with powerful antioxidants, including quercetin, lutein, and zeaxanthin,” says Newgent. Along with beta carotene, lutein and zeaxanthin are carotenoids that are believed to maintain the health of your eyes and vision as you age.
Another antioxidant present in kale is vitamin A, which has a similar function. “Vitamin A plays a vital role in your vision,” says Newgent, “as well as the functioning of cells and your immune system.”
Getting enough vitamin A in your system may also help improve your skin and hair health, too, adds Glockner.
The recommended amount of vitamin A is 700 to 900 micrograms of retinol activity equivalents (RAE) a day. One cup of cooked kale contains 172 micrograms RAE.
“Calcium is the most prevalent mineral in our bodies,” says Glockner. Along with phosphorus, she explains, calcium helps improve our bone and tooth health. “Calcium is also important for heart health and muscle contractions,” she adds.
Adults should aim to consume 1,000 milligrams of calcium per day; growing teens and adolescents should shoot for 1,300 milligrams.
One cup of cooked kale gives you 177 milligrams of calcium, which is nearly 20% of your daily intake.
Fiber has a plethora of important functions for the body. Fiber helps promote better gut health, says Glockner, and adds bulk to your stools, making them easier to pass. Plus, “Fiber keeps the tummy full longer,” she explains, “which can prevent overeating at the next meal.”
Fiber can also help regulate your blood sugar levels and prevent extreme highs and lows, Glockner adds, since it slows down the rate of glucose absorption.
One cup of cooked kale has nearly five grams of fiber, which is about 20% of the RDA for adults (25 grams of fiber for women and 30 grams for men).
Which Is Healthier: Spinach or Kale?
When it comes to leafy greens, spinach and kale reign supreme. But is one leaf healthier than the other? Glockner says no.
“One is not a better option than the other. They just have different nutrient and taste profiles,” she says. For example, “Kale is higher in vitamin C, calcium, and fiber,” she says, “while spinach is higher in iron, potassium, and vitamins A and K.”
Eating spinach and kale is a good idea if you want to score as many nutrients as possible for a low calorie count.
“The more vegetable variety you get,” Newgent says, “the more variety of nutrients you get.”