The benefits. At just 36 calories per 1-cup serving, kale is packed with vitamins A, C, and E, along with calcium and fiber. And it contains lutein, zeaxanthin, and other carotenoids, which have been linked to a reduced risk of certain eye diseases. Plus it’s loaded with vitamin K, which helps blood to clot and builds stronger bones.
There’s evidence that eating an extra daily serving of leafy greens can reduce the risk of type 2 diabetes. And the greens have glucosinolates, which might help fight cancer. “We have not seen clear benefits with cruciferous vegetables for reduction in cancer incidence in humans,” said Walter C. Willett, M.D., Dr.P.H., chairman of the department of nutrition at the Harvard University School of Public Health. “Although glucosinolates and related compounds at high doses can inhibit cancers in animals.”
People taking warfarin (Coumadin and generic) should talk with their doctor before eating foods rich in vitamin K because it can undermine the blood thinner’s effects, says Sarah Booth, Ph.D., director of the Vitamin K Laboratory at Tufts University in Boston.
Buying it. Two types are popular: curly, which is bright green and tastes a little tart, and dinosaur (also known as black, lacinato, or Tuscan), which is darker, with flat leaves and a nutty taste. All types of kale can be eaten raw, but beginners might like the more tender dinosaur variety, says Dawn Jackson Blatner, R.D., author of “The Flexitarian Diet” (McGraw-Hill, 2009).
When shopping, avoid yellow or bruised leaves, limp stems, and any signs of decay. Or try prepackaged baby kale, which tends to be more tender and less pungent than mature kale. Frozen kale is best used in casseroles and other dishes where you’re combining ingredients, as it loses some of its texture. Buy organic if it’s available.
Growing it. Although it’s usually started in the spring, late July is also a good time to plant kale, says Betty Sanders, a master gardener who oversees a 6,000-square-foot garden at the Massachusetts Horticultural Society in Wellesley. “Kale likes a light frost, which makes it sweeter," she said. "But it’s gone once the temperatures dip into the low 20s.” You can grow it in pots, but make sure that they’re roomy (a minimum of 8 inches deep and 8 inches wide) and that the plants get at least 8 hours of sunlight.
Prepping it. Store kale in an airtight container or sealed plastic bag until you’re ready to use it. Then wash the leaves before you cut them and blot dry. If you’re put off by kale’s tougher texture in raw salads, try cutting it thin and massaging in an acid-based dressing that includes lemon, lime, or vinegar. That will help break down cell walls and make it more tender, Blatner says. Because the stems tend to be tough, she strips the leaves from them whether she’s eating kale raw or cooked.
Cooking it. “You can cook kale to release the bitterness, but don’t overcook it,” Cowan said.
Bottom line. Kale is a star in the produce aisle, but don’t forget to eat a rainbow of fruit and vegetables to get all of Mother Nature’s benefits.