A new study clashes with previous research on the negative health effects of red meat
Health experts are roundly criticizing controversial new research and health advice suggesting people who eat red meat and processed meat should continue to do so, calling the research “flawed” and saying the recommendations are “irresponsible” and “dangerous” and “should be ignored.”
Both red meat and processed meat (such as bacon, lunch meats, and salami) have long been associated with an increased risk of heart attacks, strokes, and certain cancers. Health experts for years have advised limiting consumption of red meat to no more than a few servings weekly (preferably lean cuts) and reducing or eliminating all processed meats.
The newly published advice stems from five separate new reviews of existing studies, done by an international team of researchers. The reviews found that lowering red meat consumption reduced risk of cancer, heart disease, and diabetes. But the researchers conclude that the risk reduction was “very small and the certainty of the evidence was low or very low.”
“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.”
Based on the findings, the group published recommendations in the Annals of Internal Medicine:
“We made a weak recommendation that most people need not reduce their (consumption of) red meat and processed meat,” says the project’s leader, Bradley Johnston, an associate professor of community health and epidemiology at Dalhousie University in Canada. “We did not find a statistically significant or an important association with a reduction in cancer, diabetes, or heart disease when people reduced their red/processed meat intake.”
He added: “For most people who enjoy eating meat, the uncertain health benefits of cutting down are unlikely to be worth it.”
“Flawed analyses and recommendations”
“The recommendations are not reasonable and should be ignored,” says Meir Stampfer, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health. “The methodology was very poor.”
Johnston’s group left out at least two important studies that Stampfer says should have been included in their review. One of those, the comprehensive Lyon Diet Heart Study from 2001, split about 600 people into two groups and monitored them for 46 months. Those who followed a Mediterranean-style diet — including more fruits, vegetables, bread, and fish and less red meat — had a 50% to 70% lower risk of heart disease, based on actual heart attack and stroke statistics. The study was actually stopped early for ethical reasons “because of significant beneficial effects” of the Mediterranean-style diet and the negative effects to the other group.
Even without that data, Johnston’s group found 10% to 12% reductions in mortality risk for people eating less meat, Stampfer says, but they “chose to mischaracterize those as small. Those are big!”
Other nutrition researchers at the Harvard T.H. Chan School of Public Health took the unusual step of issuing a statement condemning the new work.
“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,” they write.
The Harvard nutritionists analyzed the group’s results and came to different conclusions: “We calculated that a moderate reduction in red meat consumption could hypothetically reduce mortality by 7.6% or approximately 200,000 deaths per year,” the Harvard nutritionists determined.
Wayne Campbell, a professor of nutrition science at Purdue University, said the main conclusions of the reviews are based primarily on one set of data, from the Women’s Health Initiative, which Campbell says was not designed to answer the question Johnston’s group was pursuing. The results of the reviews, therefore, don’t merit issuing any guidelines, Campbell said. “To describe them as dietary guidelines is an ill service to the genuine dietary guidelines,” he said, adding that he fears this could be “taken as a license for people to ignore credible guidelines.”
In an email to Elemental, Johnston defended his group’s research and recommendations.
“Our take is that they are frustrated because we disagree with their perspective. Our take is that they would like to persuade people to follow what they believe is the best course of action, rather than to encourage fully informed individual choice.”
Strong evidence for limiting red meat
Stampfer and others see another flaw in the new research: If a person replaces red or processed meat with something unhealthy, such as highly processed foods loaded with sugar or saturated fats, their health outcomes will be very different compared to someone who cuts back on meat in favor of a healthy plant-based diet. The new review studies “basically ignore that simple principle,” Stampfer argues.
Separately, Stampfer’s own research, published with several colleagues earlier this year in the journal Circulation, shows that substituting plant proteins for red meat decreases the risk of cardiovascular disease. People who ate more plant protein, such as legumes, soy, and nuts, had lower levels of both total and LDL (bad) cholesterol compared to those who consumed red meat.
Increasing total processed-meat intake by a half-serving or more each day raises the risk of death by all causes 13%, according to a study by another research group published in June in the journal BMJ. Similarly increasing consumption of unprocessed red meat raises the mortality risk 9%. The study examined health and survey data on more than 81,000 men and women across several years. The findings held regardless of age, physical activity, overall quality of diet, and smoking or alcohol consumption.
Stampfer acknowledges that study results often vary, and he notes that high-quality, controlled studies are almost all of short duration (the Lyon Diet study being a notable exception) because it’s costly and impractical to dictate and monitor what people eat for long periods of time. Also, health studies that are not controlled often rely on self-reporting, which can be inaccurate.
“But just because we do not have the ‘ideal’ long term randomized trial results does not mean we know nothing,” he says. “We don’t have trials for smoking, for example, or seat belt use, or a myriad of other behaviors. We have plenty of evidence that red meat, and especially processed (meat), should be reduced and limited.”
The guidelines won’t change
Groups that recommend lower intake of red and processed meats include the United States Department of Agriculture (USDA), the American Cancer Society, the American Diabetes Association, and the World Health Organization (WHO). According to a study this July in the Journal of the Academy of Nutrition and Dietetics, Americans are eating the same amounts of processed meats today as they did 18 years ago. Consumption of unprocessed red meat is down about 16% percent, with a rise in the consumption of poultry, the research team found.
Scientists don’t fully understand why red meat, processed or unprocessed, is linked to bad health outcomes. But key culprits have been clearly identified. Saturated fats, for one thing, can increase cholesterol, building fatty deposits in artery walls that can rupture, causing a heart attack or stroke. That’s why the American Heart Association’s recommendation for a healthy diet emphasizes fruits and vegetables, whole grains, low-fat dairy products, nuts and legumes and, for meat eaters, skinless poultry and fish.
That recommendation isn’t going to change based on the new research, says Alice Lichtenstein, a professor of nutrition science and policy at Tufts University and volunteer nutrition expert with the American Heart Association. Evidence is “strong” that replacing foods high in saturated fat — including red meat — with unsaturated fat “is associated with lower risk of cardiovascular disease,” Lichtenstein says.
Meanwhile, she emphasizes the difficulty of studying one type of food rather than dietary and lifestyle patterns. “Do individuals who consume burgers for lunch typically also consume fries and a soda rather than low-fat yogurt or a salad and a piece of fruit? Are they more or less likely to engage in regular physical activity and avoid tobacco products?”
Focusing on a single food or category of food, as the new research did, “is overly simplistic and serves to misinform the public,” Lichtenstein says.
The American Institute for Cancer Research (AICR) also has no intention of changing its dietary recommendations, which are “to limit red meat intake to three portions a week and eat little, if any, processed meat for cancer prevention.” AICR also issued a statement, calling the recommendations by Johnston’s group “dangerous.”
“We have strong evidence that red and processed meat increases colorectal cancer risk, which is one of the most common types of cancer,” Nigel Brockton, AICR’s vice president of research, told Elemental. “We stand by our recommendations,” Brockton says.
The cancer-risk findings by Johnston’s group are actually in line with those of the AICR, Brockton says. Where they differ is in the assessment of the evidence’s uncertainty and in the recommendations, he says.
“People love good news about their bad habits,” Brockton says. “However… since these are avoidable risks, we believe it is prudent and justified to limit red meat intake.”