Does It Matter How Much Meat You Eat?

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Dietary guidelines from health groups around the world have long advised limiting the amount of red and processed meat you eat to help reduce the risk of heart disease, cancer, type 2 diabetes, and other conditions. But a report out today challenges those recommendations, and in fact appears to give permission to eat as much (or as little) meat as you like.

The report, in the Annals of Internal Medicine, is a collection of meta-analyses, a type of study that reviews data from previous studies. The authors looked at more than 200 studies on the health effects of meat consumption and rated their quality, while also looking at research on people’s health values and preferences about eating meat. Although the researchers found some health benefits to eating less meat, they concluded that the quality of the evidence was weak and, based on their findings, issued their own recommendations: Continue eating the amount of meat you currently eat. 

“For most people who enjoy eating meat, the uncertain health benefits of cutting down are unlikely to be worth it,” says lead author Bradley Johnston, Ph.D., associate professor in the department of health and epidemiology at Dalhousie University in Canada. The researchers acknowledge, however, that some people may want to eat less meat for other reasons. “We focused exclusively on health outcomes and did not consider animal welfare or environmental issues,” Johnston says.

The findings, as well as the methodology the researchers used to evaluate the studies, left many nutrition researchers puzzled and concerned.

“One objection is that their approach to analyzing the existing research, while appropriate for drug studies, isn’t appropriate for nutrition research,” says Charlotte Vallaeys, M.S., senior policy analyst for food and nutrition at Consumer Reports. “Another is that considerable research, even the studies included in this analysis, show health benefits to reducing meat consumption.” In addition, experts say, Johnston and his colleagues mischaracterized some of the studies they looked at and left other important ones out of their analyses.

“These flawed analyses and recommendations will likely cause a great deal of confusion in the public and may do damage to current public health recommendations,” says Frank B. Hu, M.D., professor and chair of the department of nutrition at Harvard’s T.H. Chan School of Public Health. 

Flawed Methodology

At the heart of the controversy is the way nutrition research is conducted compared with research into, say, prescription drugs.

Dietary research depends largely on observational studies, which use tools such as food questionnaires to determine what people eat, and then look for links between those habits and health outcomes, such as the incidence of heart disease or cancer. Drug research, by contrast, typically relies on randomized clinical trials (RCTs), which involve giving one group of people with a certain condition a medication and another group a placebo—a type of study that allows for more precise identification of a cause-and-effect relationship.

Johnston and his colleagues rated the nutrition studies they reviewed using a system called GRADE, which ranks observational research as low-quality. And based on that analysis, the study authors concluded that any health effects due to eating meat were uncertain. 

But many leading nutrition experts say that isn’t the best way to judge nutrition research. “Observational studies can and do tell us a lot, and nutrition scientists wouldn’t want to primarily use RCTs to draw conclusions about diets because food isn’t a pill,” Vallaeys says. “Meat is not consumed in isolation, and it needs to be examined along with the other foods people eat, so you shouldn’t only rely on RCTs to study diets.”

Hu, at Harvard, agrees. “The authors dismissed massive amounts of observational data” on the grounds that they considered it to be low-quality evidence, he says. If researchers were to use the GRADE criteria to evaluate the evidence for other public health problems, such as physical inactivity, smoking, and air pollution, none of the current recommendations on those issues would be supported by high- or even moderate-quality evidence because that research also doesn’t lend itself to RCTs, Hu says.

Contradictory Data

“The more I think about these studies, the more puzzled I get,” says Marion Nestle, Ph.D., Paulette Goddard professor of nutrition, food studies, and public health, emerita, at New York University. “The data show small benefits of eating less meat. Why the negative interpretation? The papers come across as a concerted attack on dietary guidelines—national and international—on nutrition science in general, and on nutritional epidemiology in particular.”

Both Hu and Nestle point out that there are considerable omissions in the analysis. “The authors did not look at the totality of the evidence linking these meats to health outcomes, and they excluded laboratory and animal studies,” Nestle says.

The researchers also excluded studies that compared vegetarians and meat eaters, and did not look at meat in the context of the other foods people may be eating, she says. What you replace meat with—fish or vegetables vs. refined grains and processed foods—would make a difference in the outcomes. “The data did not allow us to determine if health outcomes were different based on various replacement foods,” Johnston says.

Hu adds that some of the studies that the researchers identified as meat-reduction trials actually looked at low-fat diets, but that interpretation isn’t appropriate.

Tellingly, not all of the authors of the new report agreed with the conclusions. Three of the fourteen researchers voted against the panel’s dietary recommendations. “That is very unusual,” says Hu, who was on the 2015 Dietary Guidelines for Americans committee. “Typically these types of recommendations are based on a consensus of the panel members.”

Benefits of Eating Less Meat

One of the most worrisome outcomes of this research, nutritionists say, is that people may hear researchers voicing radically new dietary recommendations, and end up concluding that it’s all unreliable.

That’s especially concerning given that the findings of the current meta-analyses show that there are indeed health benefits to eating less red meat and that those benefits aren’t necessarily very small. Using data from one of the meta-analyses, Hu says it found that a diet low in red and processed meat is associated with a 14 percent lower risk of death from cardiovascular disease, an 11 percent lower risk of death from cancer, and a 24 percent lower risk of type 2 diabetes.

Taking estimates of current red and processed meat consumption into account, he says that a moderate reduction could reduce mortality by 7.6 percent, or about 200,000 deaths per year. “Even if only half of the reduction is real, that’s still of huge public health significance,” he says. 

How Much Meat Should You Eat?

Does it matter for health purposes if a person eats three servings of red or processed meat per week or 15 servings per week, or anywhere in between? The researchers of the current analysis don’t say.

“What we say is that this should be a choice each individual makes, given the evidence regarding harms and their own feelings about the role of meat consumption in their lives and their well-being,” Johnston says. “We believe that most fully and accurately informed individuals would choose to continue their current meat consumption, and that is the reason for our recommendations.”

But other experts find that advice troubling. “The conclusions fall into the category of ‘everything you thought you knew about nutrition is wrong,’” Nestle says. But “historically, such contrary conclusions have rarely held up. Science usually works incrementally, not in one enormous reversal like this.”

Bottom line: Most people should continue to follow current dietary guidelines. “If you like red meat, eating two to four servings a week [3½ to 4 ounces per serving] is reasonable from a health perspective, but you should eat little, if any, processed meat,” Vallaeys says. “Processed meat is classified as a carcinogen by the World Health Organization.”

Other experts emphasize the importance of considering all the available research. “It is essential to evaluate the totality of information available: laboratory, animal, human epidemiology, and clinical studies,” Nestle says, “to do this in the context of what people actually eat . . . and to add in a hefty dose of common sense.”

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