Plant-based diet: why we might need it to survive as a species

The way we eat and produce food has become so destructive to the environment and our health that it now threatens the long-term survival of the human species, an international commission of 37 scientists write in a sprawling new Lancet report.

We now have so many interconnected food-related crises — climate change, pollution, and food waste, not to mention malnutrition and obesity — that it will be impossible to feed the 10 billion people expected by 2050 unless we make dramatic changes to our diets and farming practices, the researchers argue.

What’s needed, according to the peer-reviewed report, titled “Food in the Anthropocene: The EAT-Lancet Commission on healthy diets from sustainable food systems,” is a new philosophy for how to eat on planet Earth. Though there are huge variations around the world in what and how much we consume, we are all in this existential crisis together.

Which brings us to what seems to be the most controversial aspect of this report: its specific dietary advice for ensuring that everyone’s nutritional needs are met without exceeding “planetary boundaries.” To survive as a species, it says, everyone — including you! — is advised to eat mostly vegetables, grains, legumes, and nuts, and limit red meat consumption to just one serving per week.


The EAT–Lancet Commission’s Planetary Health Plate.
EAT–Lancet Commission

This “planetary health diet,” as the authors call it, is a provocative recommendation, especially for those of us in countries (like the United States) where many people eat multiple servings of meat a day. It would require a radical revamping of our food culture — prioritizing sustainability and collective survival over food hedonism and tradition.

So it’s no shocker that there’s been some pushback to the report, and not just from the usual suspects in the meat industry, who seem to feel increasingly threatened by modest increases in flexitarianism, veganism, and good old-fashioned vegetarianism. A few researchers and doctors have also quibbled with some of the details in the dietary advice, and whether we really know what a healthy diet for all humans looks like. Let’s chow down on the details.

Why the EAT-Lancet Commission is pushing a plant-based diet

After three years of reviewing what they say was “the best evidence available for healthy diets and sustainable food production,” the Lancet authors came up with a set of targets for shifting diets on an average intake of 2,500 calories a day. Funding for the initiative came from the Wellcome Trust in the UK and the EAT Foundation, the private foundation of Norwegian billionaires Gunhild and Petter Stordalen.

The targets are ambitious, to say the least.

Relative to average global consumption patterns, everyone should eat half as much red meat and sugar, and twice as many nuts, fruits, vegetables, and legumes.

Per person, this means about less than half an ounce of red meat per day, or one serving of red meat (one quarter-pound hamburger) per week. The targets are similarly stringent for other animal products, recommending less than one ounce of white meat (such as chicken), one ounce of fish, one-quarter of an egg, and 9 ounces of milk per day.


Targets for a planetary health diet, with possible ranges, for an intake of 2,500 calories per day.
EAT-Lancet Commission

According to Walter Willett, a professor of nutrition and epidemiology at Harvard University and the lead author on the report, there is strong evidence of the health benefits of plant-based diets. “Our conclusions are based on dozens of randomized controlled feeding studies that show improvements in cardiovascular risk factors with higher intakes of plant-based protein sources,” he wrote in an email.

He cited Predimed and the Lyon Diet Heart Study, two randomized controlled trials (considered the “gold standard” for evidence in health research) of the Mediterranean diet that showed benefits for cardiovascular disease risk or overall mortality. The Mediterranean diet, which emphasizes loading up on olive oil, fish, nuts, and fresh produce, is a good example of something that fits well with the report’s dietary targets, he added. (For a solid critique of the Predimed study, check out Julia Belluz’s recent piece.)

Francesco Branca, the head of nutrition at the World Health Organization and a Lancet co-author, says the report is also largely in line with WHO recommendations on fats and carbohydrates. He cited a recent systematic review of prospective studies and clinical trials published in the Lancet, which found that increasing “dietary fiber intake and replacing refined grains with whole grains is expected to benefit human health.”

But, of course, the planetary health diet is not just about human health. As Marco Springmann, a University of Oxford researcher and a member of the commission, showed in a recent Nature paper, animal products generate the majority of food-related greenhouse gas emissions (72 to 78 percent of total agricultural emissions). Even the world’s largest livestock companies, through efforts like the Global Roundtable for Sustainable Beef, admit they need to do more to reduce greenhouse gas emissions and pollution from the billions of animals they raise to sell to us.

Much of the demand for animal products comes from more affluent countries like the US — where each person ate 222 pounds of red meat and poultry, on average, in 2018. As the Lancet report argues, we’re eating far more than our fair share, environmentally speaking.

The report acknowledges that animal agriculture can be beneficial to ecosystems in some contexts. But “plant-based foods cause fewer adverse environmental effects” than animal products by every metric. “We estimated that changes in food production practices could reduce agricultural greenhouse gas emissions in 2050 by 10 percent, whereas increased consumption of plant-based diets could reduce emissions by 80 percent,” it says. So we could help limit the climate and pollution mess by scaling back meat and dairy and scaling up grains, legumes, and nuts.

Why some researchers and doctors are pushing back

According to Stanford meta-researcher John Ioannidis, nutrition science hasn’t yet been able to prove if there is a single set of nutritional guidelines as specific as the ones in the Lancet report for all humans to follow.

The problem, he says, is that the nutrition studies provided by the researchers to back up this “healthy” diet are observational, which means they can’t actually tell us whether one thing caused another thing to happen — only that two things are associated. “Much has never been tested in randomized trials and they continue to promote it as if it is solid knowledge,“ he told Vox by email.

He went on to explain that the only component of the EAT-Lancet diet that has been evaluated with large randomized trials is unsaturated versus saturated fats: “There is indeed a small/modest observed benefit for cardiovascular events but even this seems to be driven mostly by the trials that are not adequately controlled. Sugars and added sugars have been assessed in small randomized trials with mostly unimpressive results.”

Others also quibble with the report’s nutritional recommendations — including doctors and dietitians who advocate for low-carb patterns of eating, especially in an era when we are drowning in sugar and refined carbs.

In a piece for Psychology Today, Georgia Ede, a psychiatrist and nutrition consultant, writes that “animal foods are essential to optimal human health” and describes the various ways she thinks the EAT-Lancet Commission authors fail to provide adequate scientific evidence for the nutritional value of a plant-based diet. “For those of us with insulin resistance (aka ‘pre-diabetes’) whose insulin levels tend to run too high, the Commission’s high-carbohydrate diet — based on up to 60 percent of calories from whole grains, in addition to fruits and starchy vegetables — is potentially dangerous,” Ede notes.


World Resources Institute

What about all the people who are malnourished or don’t eat much meat at all?

As the chart from the World Resources Institute above shows, meat consumption varies greatly by country. And the report notes that many of the 1 billion of the world’s population who are malnourished need more animal products in their diet, not less. “In some places, like rural sub-Saharan Africa, and rural South Asia, people don’t get enough animal products to get their growth cognitive needs,” said Jessica Fanzo, an associate professor at Johns Hopkins. Stunting in kids, for instance, is sometimes associated with low consumption of animal products and other protein-rich foods.

Ultimately, the dietary guidance the report offers is meant to be flexible and tailored to different cultures and food availabilities. But there’s a clear message for wealthier countries where meat consumption is high: We will need to cut way back, as much as 90 percent.

“In the US, Australia, Brazil, and some European countries where we consume too much animal products overall, the question is can we shift to lower-impact foods like poultry and legumes?” said Fanzo. “And can we shift that equilibrium so that those who aren’t getting enough get more animal products to create more balance?”

As for how we’d get there, the report authors admit, “Humanity has never aimed to change the food system so radically at this scale or speed.” But they note that several countries — including China, Brazil, Vietnam, and Finland — have changed their food systems rapidly in recent decades (in some cases, dramatically increasing meat consumption), and there may be clues for how governments can take it back in reverse.

To shift the world to plant-based diets, we couldn’t count on individuals. Instead, we would need a wide range of policies — everything from restricting certain foods to guiding food choices with incentives. This could mean requiring unpopular methods like taxes, rationing, and mandates. The researchers also call for a global treaty to limit the political influence of the food industry — modeled on the WHO’s Framework Convention on Tobacco Control.

Feeding everyone within planetary boundaries will also mean changing agricultural practices and reducing food loss. It’s a gargantuan task, and it’s clearly not a top priority yet for most leaders (ahem, Donald Trump). Yet it’s time to get moving, time to sift through the big ambitious ideas like those in the Lancet report and figure out how to eat in ways that won’t destroy the planet. Otherwise, we might be cooked.