Last week, as Americans grappled with the prospect of presidential impeachment and the national capacity for surprise seemed fatally depleted, news came out that shook people to their core. It was about meat.
Eating red and processed meat, the headlines declared, was no longer unhealthy. It seemed—at a glance—that a bad thing was now a good thing. The stories were based on a recently published analysis of existing evidence in which one group of researchers recommended that “adults continue their current levels of meat consumption.” This conclusion—which the journal that published the research called “guidelines”—was written by a group called NutriRECS. The group was formed recently, and has not previously made recommendations about eating meat. Some of its founders, however, published a similar article in 2016 saying that evidence was too weak to justify advising people to eat less sugar.
Fox News said the new research was “reversing previous data,” and encouraged audiences to “go eat a steak.” PBS declared this another case of “ever-changing nutrition recommendations.” The New York Times called the story “a remarkable turnabout.” But who, exactly, was turning about? The guidelines were not endorsed by any established guideline-issuing medical entities, such as the American Heart Association, the American Cancer Society, the World Health Organization, or the World Cancer Research Fund International. These and others have recommend eating meat in “moderation,” based on many studies that have found heavy meat consumption to be associated with premature death, various cancers, heart disease, and diabetes.
Despite this advice, Americans do not eat meat in moderation, and never have. Since the 1960s, the per-capita intake has doubled. The average man eats more than his own weight in meat every year (even as that weight has increased by 30 pounds since 1960). Americans eat meat in quantities that are double the global average.
The new guidelines were released in Annals of Internal Medicine, a prestigious medical journal published by the American College of Physicians. Robert McLean, the ACP’s president and a rheumatologist at Yale, told me that they were the result of an editorial decision by the journal, not the ACP, but he nevertheless defended the analyses. “They did not say that eating red meat is safe,” he said. “They said that the data suggesting it’s as harmful as we once thought is inconclusive. They’re not saying to go out and eat all the red meat you want.”
Indeed, the guidelines are not telling people to eat all the meat they can. But the explicit recommendation that adults “continue their current levels of meat consumption” seems detached from any concept of what current levels of meat consumption are, or what they mean for human health. Around the world, global meat production has grown by five times since the 1960s. In the early 1980s, the average Chinese person ate 30 pounds of meat a year. Today that number is nearly 140 pounds, in a country that has grown to more than 1 billion people. Globally, meat consumption is projected to increase by 75 percent over the next three decades.
The health effects of this consumption are significant, and on track to become much more so. Yet the guidelines ignore the most important way in which food affects our bodies, minds, communities, and so much else that constitutes health.
The day before the news reports came out, on a Sunday morning, I got a frenetic call from the physician and researcher David Katz. A fellow in the ACP, he was mobilizing his colleagues internally and throughout the nutrition world in preparation for the publication of the guidelines.
Annals of Internal Medicine was, in fact, about to devote the better part of an entire issue to the consequences of eating meat. Six articles were being published by the same group of authors from NutriRECS. This is uncommon. Getting even a single study published in the journal is considered a high achievement. And the findings of the studies were, overall, predictable: High intake of meat and processed meat was associated with an elevated risk of heart disease, diabetes, and cancers—though the authors said they had “low certainty” in their own findings.
The news alerts came down to the sixth article, which was the set of “clinical guidelines.” In it, the researchers concluded that because of the “low quality evidence,” adults should continue eating meat as they do. To arrive at this conclusion, the authors used a technique known as GRADE, which subjectively evaluates different types of evidence. For example, a drug would not simply be recommended because it is effective; the amount of effect would be considered alongside things such as reliability, side effects, and other costs. Based on its analysis, the group decided that the evidence of meat’s harms to health was not strong enough to recommend that people stop eating meat altogether. And because it deemed this evidence weak, it chose to recommend that people do not attempt to change their habits.
In addition to the risks of metabolic diseases and death, these guidelines took into account a curious variable: People like eating meat. When considering people’s “values and preferences”—such as enjoyment of the taste, considering meat to be part of one’s culture, and uncertainty about how to cook without it—the researchers reported that many participants were unwilling to cut down, even when presented with information about potential negative health effects.
Typically, a medical journal publishes its findings and then gives some analysis of what those findings might mean, but it is unusual for authors to extrapolate findings into recommendations. It is especially rare when the directives bear on heart disease, the No. 1 killer of humans. And incorporating patient preferences into the guidelines themselves is controversial. History would likely be different if findings in the 1960s that cigarettes cause lung cancer had been translated into clinical guidelines where harms were negated by people’s enjoyment of cigarettes.
In an open letter to the editors of the journal, Katz and other researchers—including one of the authors of the new analyses, John Sievenpiper—objected to the guidelines as “highly irresponsible.” In a public statement, Sievenpiper said, “Unfortunately, the leadership of the paper chose to play up the low certainty of evidence by GRADE.” He suggested that even though evidence is not certain, it is not meaningless; a lack of definitive evidence that something is harmful is not itself reason to recommend that people do that thing. Other signatories of the letter included Harvard’s chair of nutrition, Frank Hu; the former surgeon general Richard Carmona; the former American College of Cardiology president Kim Williams; and the dean of Tufts University’s School of Nutrition, Dariush Mozaffarian.
Dean Ornish, a professor of medicine at the University of California at San Francisco who advocates for the medicinal value of plant-based diets, told me, “By their own analysis, the studies don’t show that there’s no benefit to cutting back on red and processed meat. So why would Annals publish this press release, and guidelines, saying otherwise?” Medical journals are not immune to the attention economy that influences all publishing, he posited, since they are judged by their “impact factor”—the number of times a journal is cited by others. (The journal’s editor, Christine Laine, said of this allegation that the new guidelines were “relevant to our readers” and displayed “methodologic rigor.”)
Gordon Guyatt, a member of NutriRECS and one of the guidelines’ authors, says he wanted to send the message to the public that there are many things science knows very little about. A distinguished professor at McMaster University, Guyatt has had an enormous impact on medicine. He coined the term evidence-based medicine, now taught in medical schools around the world, which urges doctors to do only what is clearly proven to work. The model prizes randomized controlled trials for testing drugs and clinical interventions.
With something like diet, he says, a randomized controlled trial is extremely difficult. It’s impossible to have blinded subjects (people know what they’re eating), or to ask people to change their entire diet for decades. So most nutrition evidence is based on observational studies: looking at large groups of people over time and seeing how their diet relates to their health. In that model, it’s possible to identify patterns, but it’s never possible to say with absolute certainty which element of a diet is responsible for which outcome. By NutriRECS’ standards, this means that the evidence is “low quality.”
I asked Guyatt if doctors can advise people on even something such as whether a salad is healthier than a bowl full of sugar. He said I should tell them that “the quality of evidence is low, so it depends almost entirely on their preferences.”
This is the fundamental conflict. No single news cycle is likely to change many people’s personal habits; getting Americans to eat yet more meat would be difficult. But the message that meat might now be fine for health plays into an already prevalent sentiment that nutrition research is constantly reversing itself and no one actually knows anything.
Contributing further to this sense, on Friday, The New York Times reported that Bradley Johnston, the lead author of the guidelines and a co-founder of NutriRECS, had failed to disclose his past financial ties to the food industry. In December 2016, Johnston published a review in Annals of Internal Medicine in which he said that recommendations to cut down on sugar were based on weak evidence. It relied on the same GRADE technique, and was funded by the food industry. Johnstson told the Times that his relationship with the industry ended in 2015, once he had received the funding; he has not responded to my request for comment. The editor of Annals of Internal Medicine defended Johnston by saying that conflicts are common, telling the Times that they appear on “both sides of this debate.”
Conflicts are indeed pervasive in nutrition research. They don’t necessarily invalidate data, but they still raise eyebrows when it comes to subjective analyses such as these, especially when the takeaways go against abundant evidence.
Experts have long disagreed about the exact contribution of eating meat to health, with advocates of abstinence and inundation at the tail ends of the curve. Through it all, though, Americans have always eaten more than any mainstream guideline has ever recommended.
For most of history, in much of the world, meat eating was synonymous with prosperity. Wealthy people who could eat meat regularly grew tall and strong, and the poor subsisted on porridge and potatoes, or starved. That rapidly changed in the mid-20th century, as some wealthy countries developed the agricultural and transportation technology to make fast food cheap and ubiquitous. Chain restaurants, government subsidies, and a jingoistic idea that meat is synonymous with America have ensured that consumption has grown decade over decade.
Coinciding with the rise of meat and other processed foods, heart disease surpassed infectious diseases as the leading cause of death in wealthy countries. Attempting to stem the tide, people started thinking about what they ate. Taking a nutrient-focused approach, most experts targeted one or two compounds as the possible cause of (or solution to) all our health concerns. Some recommended avoiding cholesterol and saturated fat. The American Heart Association endorsed a “low fat” diet in 1961. Others supported Atkins-style dieting, essentially the opposite, beginning in the 1960s. Today “paleo,” “keto,” and “low carb” gurus continue to tell followers that the establishment scientists have lied to them about meat’s dangers, and promote eating more saturated fat and cholesterol.
Outside of these circles, the gist of most medical advice regarding meat has been that a moderate amount of meat is not necessarily that bad for you. Although it is, some experts then add, bad for the planet. Doctors with an especially environmentally conscious bent might add that a third of the land on Earth is used to raise livestock, and that these animals are a major cause of water pollution, soil loss, and deforestation.
The crucial determinant of health is lost in this dichotomy: Environmental harms are themselves harms to human health. Annals of Internal Medicine’s new research and guidelines explicitly excluded any consideration of how meat production affects health. The idea that the effects of food are limited to nutrients was passable as scientific theory a century ago, but to ignore all this new information about how food affects our bodies is no longer an intellectually honest premise.
Animal agriculture is water-intensive and space-inefficient, and over the next three decades, the amount of land required to support livestock will quickly increase as the habitable land for humans narrows. With fewer trees, pollution and greenhouse gases linger. Inhaling pollution already kills more than 7 million people every year, mostly by way of cancer, chronic obstructive pulmonary disease, and cardiovascular disease. Currently, there are 70 billion livestock animals, and the ruminants with four stomachs are extremely inefficient converters of plants into meat. The industry generates the spectrum of major greenhouse gases. It is the primary (and growing) source of methane and nitrous-oxide gases with more intense warming impact than carbon dioxide.
In a 2017 white paper, researchers at the National Institutes of Health described the dire effects of climate change on human health. Among them are increases in severe weather events that cause people to suffer and die directly or through the loss of their homes, livelihoods, and food supplies. Mosquito-borne illnesses pose an existential threat as standing water becomes ubiquitous. Infectious diseases spread as people are displaced from their homes. Water supplies are contaminated as pesticides and algal blooms encroach on living spaces around the world. Large-scale animal agriculture is the primary driver of the antibiotic resistance that leaves people vulnerable to dying of diseases we could have easily treated decades ago.
Despite these grim warnings, the separation of “health” and “sustainability” persists today in much of the medical world. Researchers are often furthering a dichotomy that is imposed by the cattle industry and, subsequently, by the U.S. government.
The most overt example might be the Dietary Guidelines for Americans, which are written every five years by the Department of Agriculture in conjunction with a panel of academic nutrition scientists. These determine what goes into school lunches and what’s included in public-benefit programs. The most recent guidelines were written in 2015, at which point the nutrition researchers concluded that a plant-based diet was crucial to the continued existence of our species. But various Republican legislators insisted that the agencies leave this out. Then–Secretary of Agriculture Tom Vilsack and then–Secretary of Health and Human Services Sylvia Burwell ultimately blocked the guidelines from including mention of sustainability.
Harvard’s Hu, who served on the 2015 committee, has argued that his expert panel was silenced as a result of political pressure from the meat industry. “That was a missed opportunity, because our diet has an important influence on the environment and vice versa,” he told me at the time, noting that other countries had already included this in their national guidelines. His colleague Walter Willett, a Harvard professor of epidemiology and nutrition, condemned the decision as “censorship on a grand scale, again demonstrating the power of the meat industry.”
The National Cattlemen’s Beef Association, a lobbying group for U.S. beef producers, did not respond to a request for comment. The meat industry and other agricultural interests continue to emphasize a distinction between the health effects of food production and consumption. They sell beef by focusing on the benefits of protein and iron, and encourage public debate on topics such as the health effects of saturated fat. Lobbyists push for an emphasis on nutrients alone. As Hu noted, most nutrition studies abide by this framework. News coverage then does the same: Is fat good or bad for you?
This is why the multidisciplinary work of bringing together all relevant factors for health is reserved for dietary guidelines. To write such guidelines and totally omit the most pressing human-health issue of our time—under the pretense that food is only about nutrition and enjoyment—is like recommending modes of transportation based only on passenger comfort and how much joy people get from driving their own SUV.
Yet in writing the forthcoming 2020 Dietary Guidelines, health researchers now have been strictly forbidden from factoring in the environmental impact of food. The involvement of the Department of Agriculture in issuing health guidelines has always opened such recommendations up to being conflicted, but excluding the health impacts of climate change now makes any guidelines meaningless. The duality is simply obsolete; what is bad for the planet is bad for you. In a world where nutrition science can seem plagued by methodological disputes, varying interpretations of data, and conflicts of interest, this is a fact that anyone who studies food and health can no longer disagree with. Moderation will no longer suffice.