The Dangers of Superfoods

Kale is either going to kill you or save your life depending on which media report you read. Let’s sort superfood fact from fiction.

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With every health trend, every celebrity-endorsed “superfood” and faddish juice cleanse comes the inevitable backlash.

The irrigation of colons and flushing of kidneys with $10 (and typically green) juice concoctions are as dubious as they are ubiquitous, so the Wall Street Journal and Slate — to name merely two examples — took a hatchet to some of the juicers’ more grandiose health claims. In January, it was kale’s turn. A New York Times story highlighted a potential link between the trendy leafy green and hypothyroidism, fueling a flurry of concern (and some predictable outrage) from kale evangelists.

So are we being slowly killed by kale?

Well, not exactly. This is, alas, the typical superfood debate cycle: consumer curiosity, followed by claims of miracle nutritional properties, and the inevitable warning that too much of said superfood is super dangerous. Take the Daily Mail’s predictably hyperbolic headline from earlier this week: “Why so-called ‘superfoods’ could be BAD for you: Nutritionist says kale can send your thyroid haywire and quinoa irritates the gut.”

The Daily Mail’s claim was sourced to British nutritionist Petronella Ravenshear, who writes in the latest issue of British Vogue that almost all superfoods are vastly overvalued and, in some cases, could have negative health effects. According to Ravenshear, kale “can interfere with thyroid function”; goji berries should be consumed “with caution, especially if you have arthritis”; chia seeds can “inhibit the absorption of certain minerals”; and quinoa contains “potentially gut-irritating compounds.” She cites a recent study claiming that “61 per cent of people questioned had purchased, eaten or drunk a specific food simply because it had been labeled a ‘superfood.’”

But as Ravenshear points out, the problem is not so much that these superfoods are bad for you in excess—though many experts claim they can be, especially at the exclusion of other foods— but that they were declared “super” to begin with. Indeed, the misnomer itself drives excess consumption. “People read about them in the paper and think it must be better to have a lot of them and as often as possible,” Ravenshear told The Daily Beast.

Part of the media attention is driven by celebrity nutritionists like Dr. Oz, who make piles of money promoting superfoods as panaceas. (Simply Google Dr. Oz and superfoods and you’ll stumble upon several segments in which he extols the virtues of some enigmatic fruit or herb, like red palm fruit oil, which he says will “extend the warranty of nearly every organ in your body.”) And when one superfood goes out of style, another one takes its place on natural food store shelves. Kale is apparently so last year. As Ravenshear pointed out, “in January it was buffaloberries.” And sure enough, a recent headline on Business Insider declared “This Tiny Berry Is Being Called The Next Superfruit.”

On the flip side are equally over-inflated claims (also often in the form of click-bait headlines) made by superfood detractors. Endocrinologist Dr. Jeffrey Garber told NPR that the kale-hypothyroidism connection has been “overplayed.” Even if they’re not backed by scientific evidence, such claims are welcomed by former superfood worshipers who overdosed on overwrought arguments about plants and fruits with mind-bending potential. Indeed, our inboxes and spam folders brim with offers of Acai berry diets, miracle roots from the Himalayas, and anti-aging antioxidant therapies.

All of this ensures consumer confusion: someone’s always hawking a product based on elusive, too-good-to-be-true health claims, making it harder for the layman to make an educated choice. Kale will cure what ails me? But didn’t I see a headline in the New York Times claiming it might be the cause of what ails me?

Indeed, both competing media narratives are misleading. Because these stories rarely exist to benefit readers or to help them make informed health choices (unfortunately, the Daily Mail isn’t a suitable replacement for your doctor). Could it potentially be dangerous if you lived off a diet of goji berries or kale only? Maybe, but that’s the case with most everything.

It’s silly to say that vitamin-rich kale is bad for you (but saying so invites plenty of clicks). And it’s equally silly to advise a 10-day “juice cleanse” regimen without a smidgen of scientific data suggesting that such a thing is necessary or healthy.

The truth is that diet should be varied and no single vegetable produces “miracle” results.

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“As human beings we are omnivores and we can get away with a bit of almost anything,” says Ravenshear. And kale lovers can rest assured that their favorite roughage “is a superfood,” if we define superfoods as nutrient-dense vegetables. “But equally super are Brussels sprouts, broccoli and cabbage.”

If kale canonizers need another reason to switch things up a bit, it’s to prevent their beloved greenery from becoming the Gwyneth Paltrow of vegetables—something we once loved but now love to hate.