The other day, my mother asked if we should have waffles for breakfast, and my response shocked even me: “What if we had a salad?” In the weeks since Allure asked me to write about leafy greens, I’ve changed. Once a kale agnostic, I’m now a Devout Kale Orthodox. The kind of person who eats spinach for breakfast and offers unsolicited advice to strangers in line at the salad bar: “You know, romaine is actually healthier than arugula.” (I know, spoiler alert. Just sit tight for a minute.)
All the Good They’re Doing
The more I learned about leafy greens, the more of them I ate, and the more I ate, the more I wanted to eat. “It’s a virtuous cycle,” says Dean Ornish, the president of the Preventive Medicine Research Institute in Sausalito, California. “You feel so much better so quickly that it becomes positive reinforcement.” While I can’t say I felt physical changes immediately, the psychological benefits were instantaneous. Nothing makes you feel more superior than pulling out a Tupperware container of collard greens in front of your colleagues. I may have become a zealot, but as cults go, the cult of greens isn’t a bad one to be in. (Although maybe every cult member feels this brand of righteousness?)
It seems like every week there’s a new study telling us that a food we thought was healthy is, in fact, the sole reason for the decline of civilization. But think about the Leafies. There’s a reason you’ve never read a disparaging word about them. Research has shown, over and over again, that there’s practically no anatomical system that doesn’t benefit from more kale, more spinach, more watercress. They lower the risk of heart attack and stroke; they’re linked to lower blood pressure; they keep the digestive tract healthy; they help you see better; they’re protective against many types of cancer; and they even play a role in combating mental decline.
Here’s a gross oversimplification: They have pretty much every nutrient our bodies need, with the exception of protein and fat. But when I suggested to registered dietitian Tanya Zuckerbrot that I might go on an all-green diet, she quickly set me straight: “An average woman would have to eat 50 cups of kale per day to get adequate calories.” OK, so you shouldn’t eat only greens, but they actually are a good source of one kind of fat: omega-3, which is associated with alleviating everything from mood disorders to eczema. Fish is usually the go-to for this essential fatty acid, but omega-3s originally come from greens. Fish get them from eating algae, which, as everyone knows, are the salad of the sea!
One place where greens have been shown to be more beneficial than other vegetables or fruits is in the brain. Scientists are beginning to seriously examine the effects of diet on brain function. What they’re finding is great news for anyone who thought cognitive decline was due to unlucky genes. When Martha Clare Morris, a nutritional epidemiologist at Rush University Medical Center in Chicago, tracked the eating habits and brain health of almost 1,000 adults over five years, she found that those who ate one to two servings of green leafy vegetables per day had the mental abilities of someone 11 years younger than those who didn’t eat greens. “Of all of the different types of vegetables, green leafy appear to be most related to protection against cognitive decline,” says Morris.
So what is it about greens that make them so good for you? It probably has something to do with the tough life of a leaf. Think of the leaf as the engine of the plant: It’s where photosynthesis, the process of turning light into fuel for the plant, occurs. Photosynthesis creates something called reactive oxygen species, which are turbocharged free radicals that wreak havoc in cells. To combat this molecular chaos, leaves produce tons of antioxidants. “Antioxidants put the brakes on those free radicals and keep those electrons from bombarding everything in the plants’ cells,” says Auriel A. Willette, an assistant professor of food science and human nutrition at Iowa State University. Antioxidants do the exact same thing in our bodies and have been linked to all kinds of health benefits, including protection against cancer and heart disease.
Some of the most well studied are carotenoids, which our bodies convert to vitamin A. The amount of carotenoids correlates to the amount of chlorophyll. So the more chlorophyll you have, the more carotenoids there are. This is why you always hear that the darker green the vegetable, the more nutritious it is — specifically, it’s richer in carotenoids. Among other benefits, carotenoids have been found to accumulate in the eyes and prevent macular degeneration, a leading cause of blindness. While kale may have the best PR team in the flora kingdom, according to a 2014 study conducted by the Centers for Disease Control and Prevention, it’s not even close to the healthiest green. In fact, it’s less nutrient-dense than romaine lettuce. Are you done screaming into the void?
The researchers looked at how much of 17 different nutrients, including vitamins B, C, and K, were in a bunch of “powerhouse” foods. Then they ranked the foods in terms of nutrient density. The big winner was watercress, which has an average of 100 percent of the daily value of each nutrient per 100 grams. Spinach came in fifth with about 86 percent, and poor kale was way down on the list with 49 percent. According to all the experts I spoke to, this doesn’t mean we should shun kale — the study didn’t measure nutrients like carotenoids and flavonoids, in which kale is particularly high. But we should cover our bases by eating a variety of greens, since they’re basically all good for you. Even lowly iceberg lettuce was ranked above almost every fruit on the list. The extreme complexity of food and how it affects our bodies is why it’s hard to get a simple answer on whether greens should be eaten cooked or raw. While cooking at low heat can break down cell walls and make nutrients easier for the body to absorb, many nutrients, especially water-soluble ones, like vitamin C, are lost during cooking. “There’s no simple rule,” says Morris. “I recommend that people try both.”
Juices vs. Smoothies
Tempting as it is to occasionally drink our meals, experts recommend against drinking your greens. There are three basic problems with green juice: First, many of the nutrients in leafy greens, including vitamins A, D, E, and K and carotenoids, are fat-soluble, meaning they are absorbed much more efficiently if consumed with fat, which green juice usually doesn’t contain. Second, the fiber is filtered out, so you’re going to feel hungry again before you finish the bottle. Third, many contain fruit juice, which ramps up the sugar content significantly. “They might contain 30 to 45 grams of carbohydrates,” says Zuckerbrot. “That’s like taking two pieces of Wonder Bread and pouring green juice on top.” These juices will often advertise that they do not have added sugar, but of course, pineapple or apple juice has plenty of sugar on its own. If you must have your greens liquefied, doctors recommend smoothies way over juices. “I would rather have the whole vegetable blended as opposed to having a juice that is filtered,” says Eric Rimm, a professor at Harvard’s T. H. Chan School of Public Health. “Not only are you losing much of the fiber, but probably also some of the micronutrients and other compounds.”
This idea that the whole is greater than the sum of its parts is also why green supplements are not recommended. “There have been several clinical trials testing supplements where they found that even if you grind up watercress or kale, supplements have either not that much of an effect or no effect at all,” says Willette. In fact, green-food supplements might even be bad for you. While lutein, a type of carotenoid, has been shown to slow the thickening of arteries, taking carotenoids in supplement form not only doesn’t reduce heart disease but in some cases increases heart-related complications.
To bastardize Michael Pollan: Eat greens, all kinds, cooked and raw. And since you’re being so virtuous, make it easy. I hate to cook and I love kale, so I eat a lot of kale salads. I also buy my greens prewashed and chopped. Yes, it’s more expensive, but for me it’s the difference between eating them and letting them wilt in the crisper drawer. The important thing is to get greens into your body by any means necessary, because most likely we are only beginning to understand how good they are for us. Says Ornish: “Study after study shows that when people eat a plant-based diet, they feel better — fast.”
We know that what you eat affects how you look. Studies have shown that diets that are high in antioxidants and low in sugar and fat are associated with fewer wrinkles, less sun-induced skin damage, and even reduced acne. But what about bypassing the whole eating part and rubbing kale right on your face? That’s exactly what companies like Bobbi Brown, Pacifica, and Youth to the People are hoping you’ll do with their new leafy-green-infused serums, moisturizers, masks, and cleansers. The companies claim that antioxidants found in kale, spinach, and Brussels sprouts will make your skin taut, glow-y, and generally youthful. The bottom line from dermatologists: “Vitamin C and vitamin E have been used in skin care forever. Whether the nutrients come from kale or something else, they have the same effect,” says Elizabeth Hale, a clinical associate professor of dermatology at NYU Langone Medical Center in New York City. What could potentially set these products apart is that they incorporate the whole food instead of just using individual antioxidants synthesized in a lab. “It’s just like when you eat a whole vegetable. You may be getting more nutrients than we even know about,” says Mona Gohara, a dermatologist at the Yale School of Medicine.