News & Ideas

Rethinking the American Diet

Gidon Eshel
Photo by Jonathan Kozowyk

For decades, scientists have been studying the effects of what we eat on our bodies. Gidon Eshel RI '17, a geophysicist, has spent the past 10 years studying the effects of our food choices on the planet.

Oh, this is where the food is really produced in this country.

Gidon Eshel remembers well first seeing an American commercial farming enterprise. It was the early 1980s, and he was making his way across the United States, part of a years-long cycling trip around the world. Somewhere in the desert of southern California, Eshel found himself biking for several hours alongside a single trough of dairy cows. “Imagine head after head of cattle for 25 miles,” he says. “It was stunning.”

The scene affected him, and he wrote about it in letters to his mother, back home in Israel. “I described how odd it seemed to me that in the middle of this deeply arid hostile desert, there would be dairy farming, which is really water intensive,” says Eshel.

Living among Livestock

He would know: from the age of 13, Eshel grew up on an Israeli kibbutz, a complex and multifaceted agricultural commune where he helped run a dairy operation consisting of 620 to 650 cows that needed to be milked three times a day. “I used to remember each of the names of those 620 cows, and I could identify each one of them personally,” he says with a laugh. “I was crazy about the whole thing: the lifestyle, the cows themselves, the way we make and preserve food for them—I had a very unmediated connection with nature.”

Later, after four years of military service, Eshel had an opportunity to start his own herd of beef cattle, with which he lived atop a mountain in northern Israel: “Just me, the cows, and the dogs.” He lived this way, mostly alone and off the land, for two and a half years before choosing to embark on the cycling trip that would begin to open his eyes to large-scale US beef production. Paradoxically, it was during his time with the beef herd that Eshel began to phase out animal products from his diet, save for the occasional meat provided when one of his cattle became injured in the rugged environment. He refers to this as salvage eating, saying, “It was that or having the jackals eat it.”

Eshel has lived most of his life outdoors. He spent his first nine years at sea with his older sister, mother, and ship-captain father. He says that he’s always had an innate feel for the environment and could sense that human activities were affecting it in various ways: “I could see things happening but wasn’t really in the position to interpret them scientifically.”

Seeing the Science

After cycling the world, Eshel headed back to Israel to pursue undergraduate studies in physics and earth sciences in Haifa, and then to New York City for graduate studies in geophysics at Columbia University. There, he earned a doctoral degree in physical oceanography. A Harvard postdoc followed at the now-dissolved Center for Earth and Planetary Physics, at 29 Oxford Street, during which he conducted research on climate physics.

It wasn’t until 2005 that he began to see the scientific path that would bring him to his current work. Pamela A. Martin—a friend and colleague at the University of Chicago, where both were assistant professors in the Department of Geophysics—considered his agricultural and scientific background and egged him on to investigate further.

“I am of the first generation of geophysicists who had the advantage and the joy of having pictures of Earth from space—it really changed the course of the discipline,” Eshel says. “When you look at the earth from space, in the dark half-sphere you see illuminated features like cities and roads, making clear the scope of human interference with the natural world. But if you look at the day-lit half-sphere, almost the only thing that you can see related to us is agriculture.” Sensing that seeing food-production features from space had scientific implications, he took his colleague’s advice.

“At that time, no one else was quantifying the environmental impacts of agriculture through the prism of sophisticated geophysics,” says Eshel. In 2006, he and Martin published “Diet, Energy, and Global Warming” in Earth Interactions. It was the first paper of its kind, and they would go on to coauthor several more papers on related topics.

Now, a decade into this course of research, Eshel is an expert on the various environmental tolls of the mean American diet, and his data have time and time again revealed its unsustainability. “Not only was I right,” says Eshel about his hunch that the American diet is environmentally suboptimal, “but I was right to an extent that I really did not expect.”

An Environmental Crisis

The mean American diet is rich in animal products, including beef. In the United States, pastureland comprises almost 0.7 billion acres—about a third of the country’s entire surface area—yet that land contributes only about a third of the calories consumed by beef cattle. (The other two-thirds are cultivated on about 78 million acres of high-quality cropland.) Devoting this land, much of it federally owned, to cattle grazing has environmental impacts beyond greenhouse gas emissions and water usage. It also leads to wildlife displacement, among other negative effects. “These are choices, and they’re not really leading us to an optimal allocation of resources—far from it,” says Eshel.

So what do the data reveal about how best to allocate those resources? “Save going all-out vegan, the most impactful change that you can make is to ditch beef altogether and replace it with poultry—just beef to poultry,” Eshel says. “That alone will allow the United States, with current resources used, to sustain fully 120 to 160 million additional Americans.” He has taken this message to the masses in such popular documentaries as Planeat (2010) and Leonardo DiCaprio’s Before the Flood (2016).

Worldwide, the problem is even larger, particularly in the tropics. “In recent years, nearly all new deforestation has been in the name of beef production,” Eshel explains. “We’re driving species to extinction at a rate that is staggering, and it’s just for eating beef. It seems like such a poorly thought out bargain.”

The Way Forward

Eshel’s research keeps revealing the amazing effects that subtle dietary shifts can have. But should Americans eliminate beef, he asks, “what would replace it that will achieve the most impact, both nutritionally and environmentally?” This is the question to which Eshel is devoting his year as the 2016–2017 Hrdy Fellow at Radcliffe.

Currently a research professor of environmental physics at Bard College and founder of the website—which attempts to guide visitors looking for the best ways to mitigate their environmental impact—Eshel is collaborating with Harvard colleagues at the Center for the Environment and the Harvard T.H. Chan School of Public Health to unify environmental and nutritional science. “There are many people, including some very well-meaning people, who take interest in the realm of the environment and agriculture but dispense advice that is not very sound,” he says. He’d like to counteract that with solid scientific evidence showing that minimizing or eliminating animal products significantly protects health along with the environment.

It’s an ambitious goal that he hopes will reveal a more efficient and sustainable American diet. Helping him along his fellowship journey are two Radcliffe Research Partners, Paul Stainier ’18 and Akshay Swaminathan ’19. The two undergraduates have produced enough original work to write their own paper, with Eshel as coauthor, which they hope to publish before the end of the academic year. “They are phenomenal,” he says. “I’ve never seen undergraduates like this.”

Full Circle

This year, Eshel is surprised to find how much he is enjoying his city sojourn: walking around Cambridge, working out at the gym, food shopping in Central Square at H-Mart or the Harvest Co-op. It’s a lot different from his day-to-day life in the Hudson Valley, in New York. There, he lives with his family in a rural environment and bikes 16 miles to and from the Bard campus. They grow their own vegetables in the summer. “All our neighbors are farmers, every last one,” he says. “We’re the only household that isn’t. It’s an insular community where people help each other: if my neighbors’ sheep are loose, everybody will gather to bring them back in.”

The Hudson Valley is a long way from his rugged youth on the kibbutz, in the northern Israeli mountains, or cycling his way across foreign lands, but Eshel continues to live his life in a manner consistent with his upbringing. Now, however, after his years of scientific exploration, he knows the reasons behind the mysterious environmental changes he observed as a child—and his life’s work aims to ameliorate them.

Science Diet

In his very first paper, Gidon Eshel compared the mean American diet with five other hypothetical diets—and found that it releases more carbon dioxide (CO2) into the atmosphere than a vegan, poultry-based, lacto-ovo vegetarian, or pescatarian diet. (The only hypothetical diet to perform worse was one that gets all its animal protein from red meat.) In fact, compared with a plant-based diet, the mean American diet results in 1,500 kilograms of CO2 per person released annually into the atmosphere.

More-recent research has considered individual foods that consume fewer resources while delivering comparable energy and protein. Surprisingly, soybeans, tofu, and even spelt handily outperform beef on both counts.

Collaborating across Disciplines

When he’s not in his Byerly Hall office, Eshel can be found attending meals and events at the Center for the Environment, directed by Daniel P. Schrag, a friend and collaborator whom he calls “super smart” and praises for his “talent in delivering succinct and well-packaged environmental messages.” Schrag is the Sturgis Hooper Professor of Geology and a professor of environmental science and engineering at Harvard, where he also directs the Laboratory for Geochemical Oceanography.

However, Eshel’s collaborations extend across disciplines—and across the river. Eshel has tapped two faculty members from the Harvard T.H. Chan School of Public Health to ensure that his research yields nutritionally sound dietary advice that optimizes health as well as environmental outcomes. There, he’s working with Meir J. Stampfer, a professor of epidemiology and nutrition, and Walter Willett, the Frederick John Stare Professor of Epidemiology and Nutrition.

Inspiring the Next Generation

Paul Stainier ’18 and Akshay Swaminathan ’19 are Harvard undergraduates who have signed on to work with Eshel this year as Radcliffe Research Partners. Their goal is to expand on models from Eshel’s original work to consider other types of consumption. “They use my code, my machinery, but they modify it for the specific calculations at hand,” the fellow says.

“He told us that we could turn it into a paper,” says Swaminathan. “He emphasized that one paper should communicate one single idea. Although we still have a lot more to do within this meat-replacement project, we reached a reasonable milestone that merits its own analysis.”

The resulting paper, which they hoped to submit in January for publication before the end of the academic year, presents plants that have a low environmental impact in terms of production but which provide sufficient protein. Swaminathan says, “We wanted to make sure that our recommendation didn’t sound like ‘If you want to replace beef in your diet to reduce your environmental impact, you just have to eat 20 pounds of lettuce a day!’” Their results show that soybeans, lentils, tofu, and peanuts are the foods that best replace beef.

Swaminathan, a joint concentrator in statistics and molecular and cellular biology with a secondary in global health and health policy, has been a lifelong vegetarian for cultural reasons. More recently, though, “I’ve become aware of the immense nutritional and environmental benefits of a plant-based diet,” he says. “I love being able to advocate for my lifelong diet with incontrovertible scientific evidence.”

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