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How the Media Got a Study About Vegetarianism Really, Really Wrong

Like, really.

If you're the sort of person who believes bacon makes everything better, then a study that made headlines this week claiming a vegetarian diet can kill you was probably a welcome sight. Enough with this nonsense about how eating less meat is better for you, for animals, and for the planet. Vegetarianism is deadly, the headlines read.

"Long term vegetarian diet changes human DNA raising risk of cancer and heart disease," the Telegram warned. "Being a long term vegetarian changes your DNA and increases your risk of cancer" according to Cosmo UK. "Being a vegetarian could kill you, science warns," the New York Post proclaimed.


Except here's the problem: that's not what the actual study said. At all.

"In the beginning, we were pretty happy to see our research getting so much attention," Kaixiong Ye, a biology post-doc at Cornell University and co-author of the study in question, told me. "But over the last few days I have found that most of the news coming out right now [on our study] is wrong. It's kind of frustrating."

So what did the study actually find? Ye and his colleagues identified an allele—a gene variant—in some people whose ancestors maintained a primarily vegetarian diet. This allele allows these individuals to produce synthetic versions of omega-3 and omega-6 fatty acid, which are essential for brain function but can be lacking from vegetarian diets.

While a certain level of these fatty acids is necessary for your body to run, too much of it can cause inflammation, which can lead to heart disease and colon cancer. Because of this, individuals with the "vegetarian allele" would be better off sticking to a vegetarian diet, so that they're not getting double the dose of fatty acid from their diet and their body's natural synthetic version.

It's actually a really cool finding that demonstrates how humans, over hundreds of generations, can evolve traits unique to their local environment: This allele was more commonly found in individuals from more vegetarian cultures. While about 70 percent of South Asians had it, only 17 percent of Europeans (whose ancestors ate meat) did.


"Our claim is that, to put it simply: you need to have a diet that is matched to your genes," Ye explained. "For those individuals that carry the 'vegetarian allele,' our suggestion is to stick to the vegetarian diet because that's what your ancestors ate and that's what your ancestors adapted to. Too much meat or vegetable oil is not good for these people, because those foods also contain omega-3 and omega-6 fatty acids."

But somehow, this study about a gene variant that means some people might be better off eating a vegetarian diet was misinterpreted to mean that eating vegetarian will cause your genes to mutate and lead to a higher risk of colon cancer.

"There was a cascade of misinformation," said Nathaniel Comfort, the Baruch Blumberg professor of astrobiology at the Library of Congress and NASA who blogs about hype and misconceptions in genetic research. "The way this happened is through a kind of informational entropy."

Comfort said there were a number of elements that made this particular study ripe for misunderstanding. Genetics often gets oversimplified due to a general misunderstanding of how genes affect traits, Comfort told me. One single gene does not cause one single trait, and the relationship between the genes and the traits they impact is complicated, but that doesn't always make for the most exciting headline, so these kind of studies often get boiled down to labels like "the vegetarian gene," Comfort said.


"Vegetarians make us feel guilty, right?"

Nutrition studies also commonly get misconstrued because they are a popular topic, Comfort told me. Everybody eats, so everyone is interested in studies about what we put in our bodies, which means writers who don't often cover science might report on nutrition studies and make mistakes.

Then there's the vegetarian factor.

"Vegetarians make us feel guilty, right? They're so virtuous and ascetic, and yet bacon is so good, you know?" Comfort said. "Interpreting this study like this is a way for someone to rationalize their not following a vegetarian diet."

Here's the thing: the study, like lots of studies, is not exactly simple to parse. Even the title —"Positive selection on a regulatory insertion-deletion polymorphism in FADS2 influences apparent endogenous synthesis of arachidonic acid"—is, uh, cryptic. Science writers must simplify some concepts in order for any reader who doesn't have a PhD in genetics to understand. Comfort told me the key is to simplify without distorting, a challenge that requires time and research.

"We have to be careful and precise," Comfort said. "Science is an intellectual discipline that requires precision and accuracy and writing about science has to be equally careful."