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Their job was simple: Define a healthy diet.

But when 21 of the top nutrition scientists in the world gathered in Boston last week to agree upon universal principles for sound eating, more than one described their final dinner together as a cage fight.

Paleo diet partisans called for more meat. Mediterranean diet advocates argued for olive oil. Low-fat faced off against high-fat. And on. And on.


“Ninety minutes into the meeting, we were still trying to agree what the hell a vegetable was,” said Dr. David Katz, director of Yale University’s Prevention Research Center. “That was a dark moment.”

Oldways, a food education nonprofit based in Boston, had convened a two-day conference, including what turned into a four-hour dinner debate, to craft a single, clear message on healthy eating.


In the media, diet headlines flip-flop regularly — Butter is bad! No, good! No, bad! — leading to whiplash in the public and the perception that no two nutrition experts agree. Those experts worry consumers might not understand that for all the disputes, there are core principles for healthy eating, backed by solid evidence.

“We disagree about details, but we affirm that experts with very diverse perspective do have common ground,” said Katz, who co-chaired the Oldways Finding Common Ground Conference.

That was the theory, at least.

But common ground seemed elusive as the conference got underway. In the first talk, Dr. Dean Ornish of the University of California, San Francisco, advocated for low-fat, plant-based diets, which he has said can “undo” heart disease.

Ornish didn’t hesitate, either, to take a swing at the vaunted Mediterranean diet — high in fatty olive oil and cheese — arguing that while it might reduce the rate of stroke, it didn’t help other cardiovascular health measures.

That didn’t sit well with epidemiologist Dr. Miguel Martínez-González of the University of Navarra in Spain, lead author of a seven-year randomized, controlled clinical trial of the Mediterranean diet.

Martínez-González, who wore a shiny green tie that looked as if it had been dipped in the olive oil he’s so passionate about, flashed a slide he had created specifically to rebut Ornish. “I have included this table just now to address this criticism,” he said, pointing to a table of data to show that the Mediterranean diet also protected individuals from heart attack and death from cardiovascular problems.

He didn’t stop there: Martínez-González rattled off a series of findings from the last two years showing that the high-fat diet also protects from peripheral artery disease, type 2 diabetes, breast cancer, and even cognitive decline.

And the day was just warming up.

“Ninety minutes into the meeting, we were still trying to agree what the hell a vegetable was.”

Dr. David Katz, director of Yale’s Prevention Research Center

Radiologist S. Boyd Eaton of Emory University, father of the Paleolithic diet, whipped up the crowd with his claim that we all should eat what our ancient ancestors ate — namely, meat, wild fruits, and vegetables, with about 30 percent of calories from protein and a whopping 35 percent from fat. That could be an ideal paradigm for the field, he argued — an overarching perspective through which to understand and study nutrition, like the germ theory in medicine.

In the spirit of the conference, he did make a concession: Red meat, a staple of a Paleolithic diet, “is a real problem” due to its carbon footprint, said Eaton, and he proposed a more sustainable Paleo diet that instead derives its protein from plant sources, poultry, and seafood. But he still called for way more fat and protein than, say, Ornish.

Other presentations pressed the merits of vegan and vegetarian diets, and talked up the importance of the glycemic index, which measures how much certain foods raise blood glucose. (Those who follow a low-glycemic diet might eat, for instance, pasta but not bagels, parsnips but not potatoes, grapes but not raisins.)

After the presentations, over a dinner of ratatouille, couscous, and poached pear, Katz asked the assembled scientists for a consensus on a list of foods that people should eat more often. “I thought it would be easy — a softball,” said Katz.

It wasn’t.

“People got worked up,” recalled Martínez-González.

Participants said the debate was so heated that a few particularly argumentative colleagues got branded “the naughty corner.” (They didn’t name names.)

In the end, the nutritionists decided to endorse a broad set of dietary guidelines rather than try to agree on details.

The result: An 11-point consensus statement on healthy eating.

It endorsed a hefty 2015 report by the the federal Dietary Guidelines Advisory Committee, which recommends a diet high in vegetables, fruits, whole grains, low- or non-fat dairy, seafood, legumes, and nuts. The report also recommends moderate alcohol intake and low consumption of red and processed meats, sugar, and refined grains.

The consensus also emphasized that food must be sourced in a sustainable way if society is to feed future generations.

But how would the newfound agreement make it above the din and reach the public? The sixth point of the consensus begs for a consistent message from the media, rather than a rush to embrace (or reject) every new study that comes along. “We need to stop treating dietary science like a pingpong ball,” Katz pleaded.

When the consensus review was finished, applause filled the room. Katz was smiling ear to ear.

“Last night, I thought we were doomed. But I’m really impressed and satisfied,” Katz told STAT. “It is robust and meaningful.”

With that, the scientists headed toward lunch. On the menu: olives, hummus, and falafel — a Mediterranean buffet.

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