The green party
Scientists are just beginning to understand the benefits of green food, and what they’re learning will surprise you. In a good way!
afew days ago, my mom suggested waffles for breakfast, and even I was shocked at my response: “What if we had a salad?”
In the weeks since I was asked 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 tells strangers at the salad bar: “You know, romaine is actually healthier than rocket.” (I know, spoiler alert. Just sit tight for a minute.)
How good are they really?
The more I learnt about leafy greens the more of them I ate. The more I ate, the more I wanted.
“It’s a virtuous cycle,” says Dr Dean Ornish, president of the Preventive Medicine Research Institute. “You feel so much better so quickly that it becomes positive reinforcement.”
While I didn’t feel physical changes immediately, the psychological benefits were instantaneous. Nothing makes you feel more superior than pulling out a Tupperware container of leafy greens in front of your colleagues. I may have become a zealot, but as cults go, the cult of greens is a good one to belong to. (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, behind the decline of civilisation. Then think about the leafies. There’s a reason you’ve never read a disparaging word about them. Research shows, 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 stroke and heart attack risk; they’re linked to lower blood pressure; they keep the digestive tract healthy; they improve sight; they protect against many types of cancer and even help to combat mental decline. Here’s a gross oversimplification: they have pretty much every nutrient our bodies need, except for protein and fat.
But when I wanted to try an allgreen diet, registered dietician Tanya Zuckerbrot set me straight: “An average woman would have to eat 50 cups of kale per day to get adequate kilojoules.”
OK, so you shouldn’t eat only greens, but they actually are a good source of one kind of fat: omega-3, 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, the salad of the sea!
One place where greens are more beneficial than other vegetables or fruits is the brain. Scientists are beginning to seriously examine the effects of diet on brain function and it’s great news.
When nutritional epidemiologist Martha Clare Morris tracked the eating habits and brain health of almost 1 000 adults over five years, she found 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 types ofvegetables, leafy greens appear to be most related to protection against cognitive decline,” she says. So what makes greens so good for you?
Think of the leaf as the engine of the plant: it’s where photosynthesis, the process of turning light into fuel, occurs. Photosynthesis creates reactive oxygen species, 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 electrons from bombarding everything in the plants’ cells,” says Dr Auriel Willette, assistant professor of food science and human nutrition.
Antioxidants do the exact same thing in our bodies and are 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
“Those who ate one to two servings of leafy greens per day had the mental abilities of someone 11 years younger.”
“The more chlorophyll you have, the more carotenoids there are. This is why dark green veggies are more nutritious.” “Tempting as it is, experts recommend against drinking your greens.”
correlates to the amount of chlorophyll. The more chlorophyll you have, the more carotenoids there are. This is why dark green veggies are more nutritious; they are richer in carotenoids, which help prevent macular degeneration, a cause of blindness.
While kale may have the best PR team in the floral kingdom, studies show that it’s not even close to the healthiest green. In fact, it’s less nutrient-dense than romaine lettuce. The researchers looked at how much of 17 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% of the daily value of each nutrient per 100 grams. Spinach came in fifth with about 86%, and kale was way down on the list with 49%. According to the experts, 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. Even iceberg lettuce ranked above almost every fruit on the list.
The extreme complexity of food and how it affects our bodies is why it’s difficult to get a simple answer on whether greens should be eaten cooked or raw. Cooking at low heat can break down cell walls and make nutrients easier to absorb, but many nutrients, especially water-soluble ones like vitamin C, are lost during cooking. “There’s no simple rule,” advises Martha. “I suggest people try both.”
Juices or smoothies?
Tempting as it sometimes is to 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 fibre is filtered out, which means you’re going to feel hungry again before you finish the bottle. Third, many contain fruit juice, which ramps up sugar content significantly. “They might contain 30-45 grams of carbohydrates,” says Tanya. If you must liquify your greens, doctors recommend smoothies over juices.
“Rather have the whole vegetable blended than a filtered juice,” says Dr Eric Rimm, a professor of public health. “Not only are you losing much of the fibre, but probably also some of the micronutrients and other compounds.”
What about green supplements?
The 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 which found that even ground watercress and kale supplements have little or no effect,” says Dr Willette. In fact, green food supplements might be bad for you. Lutein, a type of carotenoid, has been shown to slow the thickening of arteries, but taking carotenoids in supplement form doesn’t reduce heart disease. In some cases it may actually increase heart-related complications. The solution: eat all kinds of greens, cooked and raw. And since you’re being virtuous, make it easy. I hate to cook and I love kale, so I eat kale salads. I buy my greens pre-washed and chopped. It’s more expensive, but it’s the difference between eating them and letting them wilt. The most important thing is to get greens into your body because we’re only just beginning to understand how good they are for us. Says Dr Ornish: “Study after study shows that when people eat a plantbased diet, they feel better – fast.”