Four months ago, the Annals of Internal Medicine published a controversial report that encouraged people not to worry about the health risks of eating red and processed meat, contradicting decades of nutrition advice.
The report was widely criticized by public health experts, including leading health groups like the American Heart Association and the American Cancer Society. Some experts called for the paper to be retracted, while others celebrated its findings and used it to raise questions about longstanding dietary guidelines discouraging meat consumption.
On Monday, a group of prominent researchers pushed back, publishing a large study in JAMA Internal Medicine that once again highlighted the potential harms of a meat-heavy diet. The researchers analyzed data on a diverse group of thousands of people who were followed for an average of three decades. They found that people who had the highest intakes of red meat, processed meat and poultry had a small but increased risk of developing cardiovascular disease. People who regularly ate fish, however, did not see an increased cardiovascular risk.
The new findings are unlikely to settle the debate over red meat and its link to chronic disease. But they provide further evidence for experts who argue that red and processed meats contribute to the risk of heart disease, and they suggest that health authorities are unlikely to alter their recommendations to limit meat consumption.
One of the authors of the new study, Linda Van Horn, is a member of the advisory panel that is currently helping the federal government update its influential Dietary Guidelines for Americans, which have long recommended that people limit their intake of red and processed meat. Dr. Van Horn is a member of two advisory panel subcommittees, including one that is drafting recommendations on dietary fats and seafood.
In an interview, Dr. Van Horn said that the new study relied on some of the highest quality data available. She said the findings reinforce recommendations that people should prioritize foods such as fresh fruits and vegetables, whole grains, legumes, fish, nuts and seeds and limit their intake of foods such as red and processed meats, refined grains, fried foods and sugar-sweetened beverages.
“When you eat a diet that is rich in processed and refined foods, it collectively contributes to increased risk of disease and denies you the benefits of the fiber, vitamins, minerals and plant-based proteins that contribute to health,” said Dr. Van Horn, division chief of nutrition in the department of preventive medicine at the Northwestern University Feinberg School of Medicine.
The conclusions of the new study contrast with those of the report last fall in Annals, which found that reductions in red and processed meat intake resulted in fewer deaths from cancer and heart disease but concluded that the evidence was weak because much of the data came from observational studies that cannot show cause and effect. The authors said that any increased risk was too minimal to warrant telling people that they should cut back on meat.
Critics complained that the research was flawed. They argued that the authors evaluated the evidence against meat using a tool that was designed for clinical drug trials, not dietary studies. The lead author of the report came under fire for failing to disclose conflicts of interest, including taking money from a food industry group to publish a similar paper in the Annals three years earlier that used the same methods to discredit widespread guidelines urging people to eat less sugar. In December, the Annals issued a correction on the meat paper acknowledging the lead author’s undisclosed conflicts.
The authors of the latest paper had a different interpretation of the evidence on meat consumption. Their analysis, initiated a year ago and funded in part by the American Heart Association and the National Institutes of Health, looked at data on 30,000 people who were followed for decades as part of six long-running studies on cardiovascular disease. Among the studies included in the analysis was the landmark Framingham Heart Study. Begun in 1948, the Framingham study has helped scientists identify what are now recognized as some of the leading risk factors for heart disease, such as smoking, high blood pressure, obesity, diabetes and physical inactivity.
The researchers examined the subjects’ diets and whether it impacted their heart disease and mortality rates. The study was observational, meaning the scientists could isolate links between diet and lifestyle behaviors and cardiovascular outcomes but they could not prove cause and effect. Ultimately they concluded that eating two or more servings of red meat, processed meat or poultry per week was linked to a 4 percent to 7 percent higher risk of developing heart disease. They found that the higher the intake, the higher the risk.
While many people who eat meat do not develop heart disease, the findings reflect what other large studies and scientific reviews have consistently found as well, including the recent Annals report: Higher amounts of meat intake are associated with a small but increased risk of developing heart disease.
Ultimately, whether to eat meat is for individuals to decide. Animal welfare issues are a concern for many. Sustainability issues are also a consideration, as red meat in particular has a high environmental impact.
As far as health is concerned, red and processed meat consumption is one of many overall diet and lifestyle factors that play a role in cardiovascular health, said Norrina Allen, a senior author on the latest study and associate professor of preventive medicine at the Northwestern Feinberg School of Medicine. She said that while some people might consider it a minor factor, it is nonetheless important not to dismiss.
“I would say that even though it seems to be a small amount of risk, any excess risk for something as major as heart disease and mortality is worth considering,” she said.