The Swap: Less Processed Meat, More Plant-Based Foods May Boost Longevity

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A new study published in The BMJ can't tell you exactly how much red meat is OK to eat to maintain good health or prevent disease.

But it does help sort out a big-picture, and perhaps more important, question: What does a healthy pattern of eating look like?

A diet that includes plenty of nuts, seeds, fish, vegetables and whole grains — and perhaps up to an egg a day — appears to be better than a diet rich in red meat, especially processed meats such as bacon and hot dogs.

Already a large body of evidence links processed red meats to an increased risk of heart disease, Type 2 diabetes and certain cancers.

And this new study, which included about 80,000 men and women, finds that limiting red and processed meats may help reduce the risk of premature death.

"We tracked the eating habits of our participants for several decades," explains study author Frank Hu, chair of the nutrition department at the Harvard T.H. Chan School of Public Health. This allowed Hu and his colleagues to compare people who increased their red and processed meat intake over time with those who had a relatively stable intake. On average, adults in the U.S. consume about a serving per day.

Overall, those who increased their intake of processed red meat by about 3.5 servings a week had about a 13 percent higher risk of death during the study's eight-year follow-up period.

"We estimated that when people replaced red and processed meat with nuts, seeds, fish [and other alternatives sources of protein, as well as vegetables and whole grains], they experienced more than a 10 percent reduction in their risk of mortality" during the follow-up period, Hu explains.

I asked Tom Sherman, a professor at Georgetown University who teaches nutrition to medical students, to take a look at the study. "At first, I thought, 'oh no, another paper showing that eating red meat is bad,' " Sherman wrote via email. "But in fact, this one is pretty interesting" because it looks at changes in behavior.

"Changes in behavior are fairly illuminating, and diagnostic," Sherman says. He says changes can signal that a person is starting to pay attention to one's diet — or starting to actively disregard it. And these changes "have consistently positive or negative impacts, respectively, on their risk for chronic disease: obesity, diabetes, hypertension, cardiovascular disease and cancer," he says.

This is an observational study, so it can't prove cause and effect between diet and death. But it can establish an association. Sherman says one drawback of all observational nutrition studies is that it's hard to disentangle the independent effect of changes in meat consumption from other lifestyle factors such as body weight, exercise, alcohol consumption, etc. But these new findings are consistent with a larger body of evidence.

Hu notes that in this new study, as well as in previous research, the risks associated with red meat consumption are higher — and most pronounced — with processed red meats.

"Processed meats typically contain high amounts of sodium and preservatives," Hu says. In addition, high-heat cooking methods, such as grilling, can produce carcinogens. And recent research has linked high red meat consumption — especially processed meats — with less diversity and abundance of healthy bacteria in the gut. "This may contribute to an increased risk," Hu says.

Sherman adds, "I always brace myself before sharing the data on red and processed meat consumption and mortality, CVD [cardiovascular disease] or cancer risks with my students because it sounds so unbelievably scary."

"Unfortunately," he says, "it appears to be accurate."