Study: Heart disease, cancer risk may not rise with red meat in diet

01 Oct 2019 | by Alexandra Allerton

Data from 12 clinical trials does not back up other research showing red meat increases risk for disease and death, researchers in Canada report in a new study.

  • Study: Heart disease, cancer risk may not rise with red meat in diet

Cutting back on consumption of red meat or processed meat will not significantly reduce a person's risk of heart disease or cancer, the evidence review concluded.

"Based on the research, we cannot say with any certainty that eating red meat or processed meat causes cancer, diabetes or heart disease," said senior researcher Bradley Johnston. He's an associate professor of community health and epidemiology at Dalhousie University in Halifax, Nova Scotia, Canada.

Using the evidence collected by the review, an international panel of experts have issued new dietary guidelines saying that most adults can keep eating as much red and processed meat as they like -- a recommendation that's contrary to nearly all other existing guidelines.

Among 12 clinical trials enrolling about 54,000 individuals, the researchers did not find any statistically significant or important association between meat consumption and the risk of heart disease, diabetes or cancer.

The researchers also pooled evidence from observational studies following millions of participants, and did find a very small reduction in risk among those who consumed three fewer servings of red or processed meat per week. However, they concluded the association was very uncertain.

These findings led a 14-member panel of experts from seven countries to conclude that adults could continue to eat red and processed meat as they now do.

The review focused solely on health considerations, and did not consider ethical or environmental reasons for abstaining from meat, the researchers noted.

As you can imagine, leading cancer and heart associations didn't warm to the new findings.

'The study's conclusions were reached in part because the researchers considered people's values and preferences as they crafted their recommendations. It's no surprise that people who enjoy red meat would rather keep eating it,' said Marji McCullough, a nutritional epidemiologist at the American Cancer Society.

"It's kind of like saying 'we know helmets can save lives, but some people still prefer the feeling of the wind in their hair.' And let's face it, most people will be OK, they won't crash. But everyone agrees you should wear a helmet, because public health recommendations are based on their effects on the population," McCullough said.

Study author Johnston defended the conclusions. "This is not 'just another study' on red and processed meat, but a series of five high-quality systematic reviews to inform dietary recommendations," he said.

As a result, the expert panel's recommendation on red meat is "far more transparent, robust and reliable" than other guidelines, Johnston said.

The full package of five evidence reviews and the expert panel's recommendation was published online Oct. 1 in the Annals of Internal Medicine, the journal of the American College of Physicians.

Current estimates indicate that adults in North America and Europe eat red meat and processed meat about three to four times a week, researchers said in background notes.

Many studies continue to report that red and processed meat is bad for you. For example, a Harvard-led study published June 12 in the BMJ concluded that people who increase their red meat intake by just half a serving a day boost their risk of dying over the next eight years by 10 percent.

But Bradley Johnston and his colleagues wondered if pooling the evidence obtained from high-quality studies and clinical trials might paint a different picture.

The new research runs counter to a 2015 World Health Organization evidence review, which concluded that processed meat is a proven carcinogen and red meat is a probable carcinogen, based on the evidence for colorectal cancer, McCullough said.

"Therefore, the American Cancer Society continues to recommend limiting consumption of processed meat, as well as red meat, in order to save lives from cancer," McCullough said.

"They're not saying meat is less risky," McCullough said. "They're saying the risk that everyone agrees on is acceptable for individuals."

The American Heart Association also maintains its dim view of red and processed meat.

There's strong evidence that you can improve your heart health by cutting down on saturated fat, said Alice Lichtenstein, an AHA expert and professor of nutrition science and policy at Tufts University in Boston.

"Major sources of saturated fat include meat and full-fat dairy," Lichtenstein said. "Focusing on a single food or category of foods is overly simplistic and serves to misinform the public."

One flaw of the new evidence review is that, while it included studies with vegetarian participants, it did not compare the health of those who eat meat against those who don't, said Dr. Neal Barnard, founding president of the Physicians Committee for Responsible Medicine, a group that advocates for plant-based diets.

It's true that people who eat meat less than once a week have about the same health risks as people who eat more meat, Barnard said.

But it's also true that both those groups are much less healthy than people who cut meat completely out of their diets, he said.

"The headlines are going to say 'burger lovers rejoice, you can eat all the meat you want,' and that's a completely irresponsible message," Barnard said. "The correct message is that little changes give you little results. Big changes give you big results. You can choose what you want to do," he added.

"It's the equivalent of doing a review of the benefit of cutting down on cigarettes as opposed to quitting smoking," Barnard concluded.

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