A pair of new studies out Monday might nudge you to reevaluate your meat-eating habit. One study found evidence that eating at least two weekly servings of red meat, particularly processed meat, is linked to a slightly higher risk of cardiovascular disease and death. The second links eating a diet rich in plants to being healthier.
Last September, a group of scientists stirred up controversy—and headlines—with the counterintuitive findings of their research on eating meat. Their review, published in the Annals of Internal Medicine, concluded there was no strong evidence that eating red and processed meat is bad for their health. Because of these findings, they argued that people should stay the course and not worry about cutting down on how much meat they eat.
The recommendations flew in the face of conventional nutrition science, which has long advocated that many people should reduce consumption of red meat, especially if it’s processed. Immediately, there was a backlash from other scientists and professional organizations, who questioned the design and conclusions of the group’s research. Before long, concerns about the credibility of the scientists involved in the review arose as well. One of the principal authors and his research group at the time, for instance, was found to have gotten funding from the beef industry for an unrelated study—a potential conflict of interest that originally wasn’t disclosed in the paper (a note of disclosure has since been attached).
The authors behind one of the new studies out today, published in JAMA Internal Medicine, say their work preceded any of this hubbub. But it’s a fitting rebuttal nonetheless.
The JAMA authors looked at data from six long-term studies that tracked people’s health for decades; collectively, these studies involved nearly 30,000 people followed for a median length of almost 20 years. They found that eating at least two servings of red or processed meat a week was linked to a small but noticeably increased risk of cardiovascular disease and dying early over a 30-year span. They also found an increased risk of cardiovascular disease linked to eating poultry, but not to dying early, while no risk for either was found for people who ate fish regularly.
Meanwhile, the second study out today, published in the Lancet, took a different tack. Looking at population data taken from 11,000 Americans, they studied the levels of sulfur amino acids in people, which typically come from eating animal protein. Then they found that people who had the lowest levels of these amino acids—because their daily protein mostly came from plant-based sources—were less likely to be at risk for cardiovascular or other chronic diseases compared to the average, meat-eating person.
Nutrition science, by its very nature, is imprecise. The things we eat obviously affect our health, but it usually takes years or decades for these effects to become apparent. And we can’t exactly put people in a giant petri dish and test out which foods are better or worse for us. That’s why nutrition scientists largely have to rely on population studies, which may or may not track people over time.
These studies definitely have their flaws. For one, they often ask people to remember their diets, and lots of us are notoriously horrible at remembering even what we ate this morning. These studies also can’t tell us what exactly it is about red and processed meat that can be unhealthy, though their high levels of sodium and certain nutrients that affect gut bacteria are likely culprits.
But according to Victor Zhong, a nutritional epidemiologist at Cornell University and lead author of the JAMA study, there’s enough solid evidence from these types of studies and others pointing to a clear link between poorer health and regularly eating red and processed meat.
“Convincing and consistent data have shown that consuming unprocessed red meat and processed meat is associated with a small increased risk of cardiovascular disease and death,” Zhong told Gizmodo.
Zhong is also among the many scientists who have argued that the authors behind the review last year wrongly chose to devalue evidence from population studies, which led them to conclude there were no health concerns linked to eating meat.
So where does that leave the typical meat lover? Well, Zhong and his team are careful to point out that no single food is going to make us less healthy or raise our risk of chronic illness by very much. In their study, they found an absolute increased risk of cardiovascular disease or dying early of less than 2 percent over a 30-year span linked to eating two servings of red or processed meat a week.
In a country of over 300 million Americans, though, that increased risk still adds up to plenty of people dying or having a heart attack every year who could have avoided their fate. Given other health problems linked to a diet high in processed foods, like obesity, it’s fair to say that many of us could stand to make our diets richer in plants, no matter how specifically bad red meat might be.
Zhong, for his part, is clear about what he thinks people should take away from the controversy over eating red meat.
“People can ignore the recommendations given by the reviews [in the Annals], because these reviews have serious flaws and thus the resulting recommendation is invalid,” he said. “Limiting or stopping eating unprocessed red meat and processed meat is an appropriate recommendation given the current evidence.”