It was on a warm spring afternoon last year that I realized I’d become something of a greens fanatic. Invited to an "almost summer!" barbecue, I arrived with my potluck side dish and looked around the buffet table to see all the usual suspects: potato salad, pasta salad, rice salad, green salad, chips and salsa, baked beans. I made room for my gratin of Swiss chard and kale, which I thought looked great—the Parmesan-and-breadcrumb topping browned into a lovely crust. But immediately I wondered: What had I been thinking, bringing a slab of cooked greens to this ritual offering of grilled sausages and vegetarian "not dogs"?
I mean, everyone knows greens are good for you, and some folks probably eat them out of duty, but they’re not quintessential party food. With the exception of bite-size triangles of spinach in phyllo, I can’t remember cooked greens making it onto the menu at many gatherings I’ve been to. And yet there I was with my chard and kale and the realization that I must have some subconscious desire to convince my friends of the glories of greens.
Leafy greens are among the most nutritious foods you can eat. A half cup of cooked Swiss chard, for instance, provides more than 150 percent of the recommended daily value for vitamin K, which your body needs to maintain bone health; 55 percent of the daily value for vitamin A, important for vision and healthy lungs; and 26 percent of the daily value for vitamin C, necessary for a robust immune system. Chard is also an excellent source of minerals like iron, potassium, and magnesium, as well as a great way to increase fiber intake. And you get all of that good-for-you stuff in just 18 calories!
Chard, collards, kale, spinach, mustard greens, and turnip greens have all made it onto the World’s Healthiest Foods list, compiled by the George Mateljan Foundation, a nonprofit dedicated to providing unbiased nutrition information to consumers. The foundation ranks these greens among the most nutrient-dense foods around—calorie for calorie, they give your body more of what it needs than most other foods.
(Mateljan, who founded and eventually sold Health Valley Foods—one of the first purveyors of packaged health foods—is a longtime advocate of the idea that good food choices make for healthier people. He established the foundation to educate people about healthful eating, and it funds and operates the World’s Healthiest Foods site. See World’s Healthiest Foods for nutrition information about these greens and a list of other healthy foods.)
I didn’t share any of this data with my BBQ buddies, though. Instead, I watched in disbelief as the gratin was devoured. Even the kids came back for seconds, and soon mine was the only clean platter on the table. Clearly the dish won fans based on its divine flavor—any healthful properties were only a bonus.
The Calcium Connection
On a morning walk, I told my neighbor Kay that I’d found myself serving greens to everyone I could. I was growing dinosaur kale and rainbow chard in my garden, and so I’d sautéed the chard with golden raisins and pine nuts for a few friends, stir-fried the kale with mushrooms for my family, and made a repeat of the gratin, which my daughter and her preschool pals had gleefully gobbled up. I was loving the fact that my friends and family were getting the health benefits of greens—and enjoying their flavors.
I also appreciated the ease of growing them: Put in a couple of plants, and snip a few leaves when you’re ready to cook. My sister managed to keep kale growing in a cold frame through a New Jersey winter, and my old-timer gardening friends in California taught me to never uproot a chard plant; apparently, the older the plant, the sweeter its leaves.
Kay, a nurse midwife with a keen interest in nutrition, mentioned that she favored kale and collards over Swiss chard and spinach because the latter have fairly high levels of oxalic acid. The acid can bind with calcium and prevent your body from taking in much of the calcium present in those vegetables.
As a woman in her 50s, Kay is concerned about getting enough calcium to prevent osteoporosis—but Americans of all ages would be wise to pay attention to their calcium intake. "In our culture, the decline of milk consumption that has come about with the popularity of soda pop has meant that a lot of people aren’t getting enough calcium," said Debra Boutin, a registered dietitian and an assistant professor of nutrition at Bastyr University. The USDA recommends 1,000 milligrams per day for most people.
I knew that some leafy greens are high in calcium—a half cup of cooked collards provides 179 milligrams—but I’d never heard of the calcium-oxalic acid connection and decided to do some research. As it turns out, oxalic acid does not generally cause problems for people—except those with compromised kidneys, whose doctors may recommend avoiding foods with high levels of oxalates.
But it’s handy to know that Swiss chard, beet greens, and spinach all have relatively high levels of oxalic acid. "If those were the only three greens you ate, you wouldn’t be getting the maximum calcium you can from greens," Boutin said. "And you can definitely meet your calcium needs without dairy," she added. "Greens are an excellent source." A cup of cooked kale, for instance, contains 90 milligrams of calcium, about one-third as much as a cup of milk, but with no saturated fat.
Boutin, though, didn’t agree with Kay’s approach of cutting out greens with high levels of oxalates. "Those three are excellent food sources of other nutrients, including vitamin A. So don’t eliminate them; just don’t count on them as your main source of calcium that day."
Stephanie Gailing, a certified nutritionist and a consultant to the World’s Healthiest Foods site, offered more advice: "You can reduce the oxalic acid level by cooking spinach, beet greens, and chard." Boil the greens in an uncovered pot for one to three minutes, and you’ll even find they taste sweeter, too, as the oxalic acid leaches into the water. And cooking your greens at a temperature greater than 165 degrees Fahrenheit for at least 15 seconds will kill any E. coli bacteria that might be present, too. (Water boils at 212 Fahrenheit.) But watch the clock: The longer you cook any plant foods, the fewer nutrients they retain.
In my childhood home, where salads and fresh homegrown veggies like zucchini and string beans were served nightly, the only cooked leafy green we dined on was spinach—a frozen square boiled in water, drained, and garnished with a pat of butter. (My poor mom was treated to an endless supply of overcooked turnip greens by my southern belle grandmother and has never really embraced cooked greens.) It wasn’t until I moved to Manhattan for college and discovered spanakopita, "white pizza" topped with spinach, and the 1980s phenomenon of wilted spinach salads that I started to appreciate cooked greens.
Back in foodie San Francisco, I developed a taste for broccoli rabe quick-sautéed with garlic and lemon. And when I lived in Argentina—a vegetarian among meat lovers—I became dependent on tarta pascualina: a vast quantity of extremely salty Swiss chard and whole hard-boiled eggs, packed into pie dough.
These days I put greens in soups from miso to minestrone, in stir-fries and pasta sauces, and often I sauté them, adding caramelized onions, feta cheese, olive oil, and balsamic vinegar, or orange zest, lemon juice, and pine nuts. Gailing, the nutritionist, tells me that my taste for citrus and oils with greens is a healthy one: A good squeeze of lemon can boost your body’s ability to absorb the high amounts of iron in spinach. "When vitamin C is ingested with non-heme iron [the type of iron in plant foods], absorption can be greatly increased," Gailing said.
And drizzling oil onto greens increases your absorption of carotenoids, the phytonutrients in plant food that are among the body’s strongest allies in fighting disease. "Adding oil after cooking greens is definitely a way of upping the nutritional value," Gailing told me.
Georgeanne Brennan, who wrote Great Greens and lives on a small farm in Northern California, says she eats spinach almost every day. Often she’ll just quick-boil it, but occasionally she’ll make creamed spinach, spinach lasagna, or spinach crepes. And she often uses greens as the base for beautiful, nutritious one-plate meals.
"Make a bed of lightly braised stir-fry greens and top them with slices of grilled eggplant, tofu, red pepper, and a sprinkling of sesame seeds," she suggested. "Or cook down tomatoes, peppers, onions, and some fresh oregano. Mound some arugula on the plate, then top it with polenta and the tomato mixture." In her cookbook she gives a recipe for wilted arugula topped with butternut squash and toasted pecans.
The gratin recipe I discovered last year in Great Greens has become a true family favorite. Although it requires cooking the greens a bit longer than a nutritionist might like, its ability to win over the taste buds of even the most finicky of diners is worth it! It just might inspire a lot more people to go green.
The recipe calls for Savoy cabbage and Gruyére cheese, but I’ve made it with whatever greens and cheeses were in the fridge—kale and Parmesan is a favorite—adding garlic or onions or mushrooms, depending on what I’ve had. Brennan was delighted when I told her of my various adaptations. "My inspiration for that recipe came from France, where I’ve had a house for many years," she said. "The way people cook in the country is with whatever is on hand. You’ve got a little milk, flour, some stale bread, hard cheese." Add a bunch of greens and… voilá! It tastes good enough for a party.