Editor's note: This story was updated Oct. 7, 2019 with a report from the New York Times about a potential conflict of interest for the lead researcher on the meat studies, Bradley Johnston, PhD.
Sept. 30, 2019 -- A group of papers about red and processed meat and human health, released today by Annals of Internal Medicine, says it’s OK to eat them because researchers couldn’t find any links to health problems like heart disease and cancer.
Not surprisingly, the studies have created an uproar among leading health and nutrition researchers who have long said eating too much of them is bad for your health. Several groups, one of which includes an author of one of the papers, sent letters to the journal’s editor requesting that publication be postponed for further investigation.
“It’s the most egregious abuse of data I’ve ever seen,” says Walter Willett, MD, DrPH, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, who was among the signers of the letter. “There are just layers and layers of problems.”
The papers gathered data from existing studies to analyze the links between eating red and processed meat and life-threatening conditions like cancer, heart disease, stroke, and diabetes. They found that the evidence was too weak to say for sure if there was a link. The articles included five meta-analyses -- or studies of studies -- and reviews of existing data plus a set of guidelines. NutriRECS, which describes itself as “an independent group with clinical, nutritional and public health content expertise,” produced the studies. An editorial about the findings accompanied the articles.
The NutriRECS guidelines recommend that adults don’t change the amounts of red and processed meat they’re eating. That contradicts the federal government’s Dietary Guidelines for Americans, advice from the World Health Organization, and numerous studies and books published over the last decade, all of which point to the health and environmental benefits of eating less meat and more plant-based foods.
“Our approach has been very different than previous approaches,” says Bradley Johnston, PhD, an author on all six papers and a co-founder of NutriRECS. “We’ve taken the individual approach rather than societal. We believe that people should be fully informed when they make health care decisions based on best estimates of data, how certain we can be in that evidence base. What has come before us often has no assessment of certainty of evidence, or if there is, it’s often unreliable.”
At least six organizations have prepared statements or reached out to Christine Laine, MD, editor-in-chief of Annals of Internal Medicine, about the articles. In a letter sent to her by True Health Initiative (THI), an organization dedicated to fighting preventable diseases, a group of 13 prominent doctors and researchers sought “to request and recommend that the Annals preemptively retract publication of these papers pending further review by your office. We do so on the basis of grave concerns about the potential for damage to public understanding, and public health.”
In addition to Willett, signers of that letter include David Katz, MD, immediate past president of the American College of Lifestyle Medicine and founder and president of True Health Initiative; Dean Ornish, MD, founder and president of the Preventive Medicine Research Institute; Richard Carmona, MD, former surgeon general of the United States; and Frank Hu, MD, PhD, chairman of the Department of Nutrition at the Harvard T.H. Chan School of Public Health. The list also includes John Sievenpiper, MD, PhD, of the University of Toronto -- an author of one of the NutriRECS papers.
Among the concerns:
Omitted studies. A list of 15 studies that seemingly met the criteria for inclusion in the analyses accompanied the True Health Initiative’s letter. Several of them, including the Lyon Heart Study, have long been considered benchmarks in the field. If it had been included, THI’s letter says, the results would have been very different. The Lyon Heart study found that eating a Mediterranean-style diet -- more fruits, vegetables, and whole grains, and less red meat -- helped prevent heart disease.
Incomplete picture. Because the analyses didn’t dig into what else participants were eating, the NutriRECS researchers asked the wrong question, says THI. Were they replacing red meat with tofu, or fried chicken? “The right question would be to compare people eating red meat and processed meat to people eating a plant-based diet,” Ornish says. “It’s a very different conclusion.”
Inappropriate analysis. The papers used an assessment method known as GRADE (Grading of Recommendations, Assessment, Development and Evaluations). It prioritizes evidence from randomized controlled trials, in which researchers randomly assign participants to groups receiving different treatment, and tracks what happens to them. That type of study is considered the most rigorous way of finding out whether a cause-and-effect exists.
But there are no randomized controlled trials examining eating beef and its link to diseases like cancer and diabetes, “Because it’s probably impossible. You can’t keep people on specific diets for years and track,” says Willett. “I doubt we’ll ever get such a study.” GRADE rates the data from the types of studies often used in nutrition as low- or very low-certainty, which could explain why the analyses found no clear connection between disease and eating meat.
Others have questioned the how accurate nutrition studies based on observational data are. Many use data based on asking people to remember what they ate, which can be unreliable. Media coverage can distort the findings. Others may be funded by industry.
But most guidelines don’t depend on those observational studies alone -- they also take into account randomized controlled studies of things like high blood pressure, which is considered an intermediate step toward heart disease, says Sievenpiper.
Contradictory data. When the True Health Initiative members took a closer look at the data in the papers, they found very clear connections between eating more meat and processed meat and risks for death, heart disease, cancer, and diabetes. The GRADE system’s preference for randomized controlled trials allowed the authors to discount those results from the observational studies.
Sievenpiper, an author of the paper that looked at eating meat and the risk for heart and metabolic diseases and cancer, says the results of his paper don’t fit the NutriRECS guidelines, which he did not work on. “I certainly do stand behind our paper, in that we did show important beneficial associations with lower red and processed meat intake and all-cause mortality,” he says. “But I don’t support the overall conclusions being drawn, or the recommendations being made.”
Confusing message. Many of the experts worried that these new studies could cause serious harm, if people take the guidelines to mean that they can eat as much meat as they want.
“It leads back to this misconception that nutrition is hard and confusing, that we don’t know how to eat, that doctors can’t agree,” says Jennifer Lutz, executive director of True Health Initiative. “We do know the best diet for human health and also the planet: plant-based. We are not a vegan or vegetarian organization. We have council members who are paleo. We believe in the spectrum, that there’s more than one way to be healthy. This idea we’re arguing is nonsense. There’s disagreement, but there is consensus.”
Unusual inclusion. One of the reviews looked at people’s attitudes about eating meat. Predictably, it found that omnivores are reluctant to give it up, even if they know their health is at risk. These results were factored into the guidelines, essentially saying that since people don’t want to give up meat, they don’t need to.
A statement about the studies from the Harvard T.H. Chan School of Public Health addressed the problem: “Although taste preference is important for personalized dietary advice, it is questionable whether it should be considered as a major factor in developing dietary guidelines.” Many people don’t want to quit smoking, stop drinking, or exercise more, Sievenpiper pointed out, but that doesn’t change the recommendations.
Ignoring the Environment. “Considerations of environmental impact or animal welfare did not bear on the recommendations,” the NutriRECS authors wrote. Livestock accounts for 14.5% of global greenhouse gas emissions, and multiple commissions have called for eating less meat to help save the planet. “This is unconscionable unless the panel members are not aware of or deny the negative impact of high red meat consumption on the environment,” says the Harvard statement. “Climate change and environmental degradation have serious effects on human health, and thus is important to consider when making recommendations on diet.”
Ultimately, the journal editor held firm against pushback. “This pre-publication campaign to ‘retract’ the articles prior to publication is not the appropriate way for scientific discourse to occur. Those involved in the campaign who are researchers themselves should know better,” Laine wrote in a statement.
Johnston, the driving force behind the cluster of studies, dismissed the criticism. “One would anticipate that experts that have previously made positions repeatedly in the literature and publicly, if the evidence is contrary to what they’ve said, there could be strong reactions,” he says. “This is human nature, I think.”
After the study published, the New York Times reported that Johnston had received funding from an industry-backed group, the International Life Sciences Institute, for a sugar study published in 2016. That's something researchers say should have been disclosed on the current study, as they are required to report any conflicts of interest in the past three years. Johnston said the group had no influence on his meat research and that he received the funding in 2015, outside the 3-year reporting window.
Should You Keep Eating Hot Dogs?
Dozens of researchers, experts, and governmental authorities say to cut back on red and processed meat, to protect your own health and the planet’s. “There’s nothing new here, no breakthrough. We know over 80% of preventable illness and chronic disease can be improved or prevented by lifestyle intervention,” says Lutz.
She says the researchers didn’t use proper methods to come up with their conclusions.
“It’s very exciting and attention-grabbing to say there’s no need to reduce meat intake. It’s less exciting to say we reviewed studies to evaluate the validity using a system not meant to evaluate the validity of these studies, and what we found is nothing.”