Get Over Kale

An otherwise worthless vegetable reminds us why nutritional studies are unreliable

Photograph by Bobbi Bowers
Photograph by Bobbi Bowers

It’s difficult to pinpoint exactly when the kale obsession began, but the most common guess is 2013—the year national kale day was founded, and the year Oberon Sinclair started making international headlines. Sinclair, a former Chinese soap opera star who now runs a New York-based PR agency, told the media that she was hired by the “American Kale Association” to make the vegetable cool (though it was later revealed that she made up the organization as part of an elaborate ploy to convert people to her love of roughage). That same year, custom “Kale(ing) Me Softly” T-shirts and articles preaching the miraculous benefits of kale prompted more and more people to incorporate the leafy green into their diets. Pizza Hut, formerly one of the largest buyers of kale in the US, was quickly outstripped—the chain had used it primarily as a garnish around their salad bars.

Suddenly, the vegetable was a transcendent force, the subject of Instagram photography and celebrity endorsements. Gwyneth Paltrow credited kale for her fitness magazine-worthy body, and Beyoncé wore a “KALE” sweatshirt in one of her music videos. Restaurants and juice bars followed suit, with establishments dedicated entirely to kale-based dishes popping up in Daytona Beach, Portland, Toronto, and Los Angeles. A 2015 report published by a restaurant research firm noted that the presence of kale on Canadian menus grew 122 percent over a two-year period. It was sautéed, baked, dipped in chocolate, mixed in cocktails, and added to smoothie concoctions resembling sewage sludge. Regardless of whether consumers were aware of the heath benefits (kale is high in iron, fibre, potassium, and vitamins C, K, and B6), all of the evidence suggested it was something we should be eating.

Ernie Hubbard disagreed. In 2015, the molecular biologist published controversial research implying that eating too much kale could be linked to low-level thallium poisoning, eventually causing chronic fatigue, neurological disorders, heart abnormalities, or hair loss. Other studies arrived at similar conclusions about high thallium levels in certain leafy vegetables. The toxic grey metal is often used in rodent poison and pesticides, though most experts say the average person would need to consume more than 150 pounds of kale for it to be a health-hazard. A handful of well-regarded publications advised people to stay away. Other sources moved on to “the new kale”—cauliflower, kelp, dandelions, and broccoli leaves have been cited as up-and-coming trends.

The verdict on what we should be eating seems to change weekly. One day, an ordinary food can supposedly add years to your life, make your smarter, and give you better skin. Then that same food gets grouped in with rat poison. Put simply, there are too many studies. In 2015, researchers in Finland and California conducted a metastudy that found an “exponential growth in the number of publications.” By some estimates, 2.5 million scientific papers are published every year. And experts continue to try and quantify what we should and should not be putting in our bodies—often with contradictory results.

When coffee first became popular in North America, it was immediately the subject of debate; some coffee drinkers suspected it gave them good manners and better breath, but doctors compared it to poison. A 1912 issue of The Salt Lake Tribune advised anxious women to avoid caffeine completely in case of “nerve storms.” To date, approximately 19,000 studies have been conducted on whether coffee should be part of our morning routine. Dutch researchers found that people who consume several cups per day were half as likely to develop type two diabetes, while an Australian study claimed that drinking more coffee was linked to weight gain and an increased risk for diabetes. Some scientists have linked it to cancer, others have deemed it a preventative. Which is it?

More often than not, food studies go beyond the nutrition label. We know that coffee contains antioxidants, and we know that’s a good thing. But we also know that those who are consuming five, six, or even ten cups every day have certain dietary patterns. These people tend to be busy, stressed, and more likely to eat on-the-go. In most cases, the bad habits associated with coffee are more likely to lead to health problems—not the coffee itself. In the case of heart disease, coffee is only associated with higher risk for people who aren’t genetically able to break down caffeine.

Like coffee, red wine contains antioxidants further associated with heart health. Wine started to become a dietary staple during the middle ages and is now closely connected to the Mediterranean diet, which recommends (at least) seven servings every week. Since the ’60s, when American scientist Ancel Keys released findings showing that poor populations in small Mediterranean towns were healthier than the wealthiest people in New York, the diet has been associated with vitality and a longer life expectancy. In 2011, researchers from Sweden’s University of Gothenburg published several decades’ worth of research on the dietary patterns of 1,200 participants over seventy. They found that those who ate like the Greeks tended to live three years longer than their Western food-consuming peers.

In an attempt to convince remaining skeptics of the health benefits associated with the Mediterranean diet, the New England Journal of Medicine monitored more than 7,000 patients at-risk for heart disease and strokes over a five year period (the first of these studies done at such a large scale). The results confirmed that, yes, people who eat the foods that make up the Mediterranean diet—fruit, vegetables, fish, olive oil, and of course, red wine—are up to 30 percent less likely to develop cardiovascular issues.

But last year, Dame Sally Davies, one of Britain’s top doctors, made headlines with a new study that warned wine enthusiasts about an increased risk of breast cancer. Davies appeared in front of MPs to defend her research and, soon after, the government changed its drinking guidelines, advising that there’s “no safe level of alcohol consumption.” However, people tend to skip the fine print when they see new studies surfacing on the web: Davies’ research only showed a 1.7 percent increased risk.

“Red wine is good if you if you’re following the recommendations,” says Caroline Richard, a registered dietician from Quebec City. Canada’s Low-Risk Alcohol Drinking Guidelines recommend no more than ten drinks per week for women, and no more than fifteen for men. When drinking habits morph into drinking problems, that’s when we start to see negative health effects, she says.

Keys, the same scientist who noticed health discrepancies between the American and Mediterranean diet, has also been credited as the person who started the war on fat. His famous study, which compared the diets of middle-aged men in seven countries, was one of the first to draw a connection between saturated fat and heart disease. During the ’70s, when the US government poured $150 million into additional studies on saturated fat, it was vilified as a leading cause of heart attacks in North America. For nearly four decades, this research was considered to be reliable. Food companies started supplying grocery stores with “light” alternatives: fat-free yogurt, skim milk, egg whites, and margarine became household staples (by some estimates, the market for artificial fat-replacers grows 5 percent each year). But a set of documents released last year suggested that some of this research was heavily influenced by the sugar industry. In a widely publicized 1967 study, Harvard scientists were paid $50,000 to understate the connection between sugar and heart disease, instead pointing the finger towards saturated fat.

Rather than replacing fatty foods with fruit or vegetables, people started eating more carbs and sugar. Those refined carbs can alter blood chemistry, tricking our bodies to feel hungry more often—which could explain why the obesity crisis in the US started in the late seventies. Between 1980 and 2012, diagnoses of type two diabetes increased 166 percent, and heart disease is currently the leading cause of death for people of most ethnicities in the US. A more recent study, published in the British Journal of Nutrition, found that people in European countries who eat the most saturated fat have the lowest risk of heart disease.

Grapefruit provides us with the oldest and perhaps most notable example of food-study inconsistency. Early twentieth century nutrition journals claimed it could heal chronic diseases and ease nausea. By the time the influenza epidemic of 1918 hit North America, the fatally ill looked to the supposed miracle produce, causing supermarkets to sell out in less than ten days. Then, a decade later when grapefruit was suspected to have fat-burning properties, people found themselves consuming as many as twenty-one servings per week—raw, juiced, or boiled.

The notion that eating more grapefruit was good for your health stuck around. Photos of pink citrus started appearing more frequently in cookbooks and women’s magazines. When a diet pill called “Grapefruit 45”—made from grapefruit extract—surfaced in the ’80s, the company spokesperson, a middle-aged man with a prominent moustache and a comb over, claimed “major research studies prove pound after pound can be lost with grapefruit.”

Grapefruit is high in essential vitamins, fibre, potassium, and antioxidants. But does it deserve its longstanding reputation? Prior to 2006, most studies arrived at the same answer: it’s a good idea to incorporate more grapefruit into your diet as a low-calorie, nutritious food. This was thought to be true for years—until a wave of later research suggested that the beloved fruit could kill you.

In a study published in the British Journal of Cancer, scientists linked increased grapefruit consumption to a rise in estrogen levels in postmenopausal women, which has been associated with breast cancer. Then, in 2012, Canadian researchers found that eating grapefruit can cause detrimental side effects when mixed with forty-three different drugs, including some birth control pills and sleeping pills. After the headlines surfaced, conspiracy theorists even suggested grapefruit was what really killed Michael Jackson.

With all of the contradictory research out there, how do we know what we should be eating? Will kale make us bald? Will coffee make us fat? Will red wine give us cancer? University of Toronto nutritional sciences professor Ahmed El-Sohemy says that it’s nearly impossible to arrive at a definitive conclusion when it comes to food assessment because we all break down nutrients differently. “Unless you know what happens to you as an individual, you’re only just guessing,” he says. “There are so many aspects to our diet and there is so much advice coming to us from all angles. It’s hard to know what to focus on.”

Consumer habits are rooted in the idea that people are improvable: Anyone can be slimmer or stronger, if they eat this or buy that. Food studies feed into these ideals about health and fitness, of that never-ending search for perfection. But ultimately, the study of nutrition is riddled with trial and error; it responds to the constant pursuit of the next big trend, and the obsession that inevitably follows. So feel free to break that well-intended New Year’s resolution and ditch the superfood smoothie—it probably won’t be healthy in 2018.

Nicole Schmidt
Nicole Schmidt is a freelance writer, editor, and fact checker based in Berlin. She was previously an associate editor at The Walrus.