The debate over the health risk of eating red and processed meat hit a fever pitch last November when the Annals of Internal Medicine published a controversial study — one based on a series of systemic reviews and meta-analyses of several previous studies — that said the dangers of meat consumption were overblown and relied on faulty research.
The pushback against that study was quick and severe. Critics claimed it had used flawed methodology to reach its conclusion. They also pointed out that the study’s lead author had research ties to the meat and food industry.
Well, the scientific quarrel about what role meat should play in a healthy diet intensified again this week with the publication of another meta-analysis, this time published in JAMA Internal Medicine. Its findings clash with the November study.
The new study reports that eating two servings of processed meat, red meat or poultry (but not fish) each week raises the risk of developing cardiovascular disease by up to 7 percent. It also found that eating two servings of processed and red meat (but not poultry or fish) is associated with a 3 percent increased risk of dying early from all causes.
Translated into absolute terms — in other words, what those findings say about the risk for any individual — the increase is even more modest. It means that eating two servings of meat a week elevates the risk of cardiovascular disease by less than 2 percent.
Still, given how popular meat consumption is the U.S. — and the fact that about 1 million Americans are diagnosed with cardiovascular disease each year — that increased risk is still large enough to have an impact on many people’s lives.
“It’s a small difference, but it’s worth trying to reduce red meat and processed meat like pepperoni, bologna and deli meats,” says Norrina Allen, the study’s senior author and an associate professor of preventive medicine at Northwestern University, in a released statement. “Red meat consumption also is consistently linked to other health problems, like cancer.”
The new study pooled data from six different studies involving almost 30,000 middle-aged U.S. adults. All had been free of cardiovascular disease when they entered the studies (in the 1980s, 1990s and early 2000s). Their average age at that time was 54. More than half (56 percent) of the studies’ participants were women, and 30 percent were non-white.
The participants provided detailed self-reports about their daily diet. A single serving of meat was defined as having the following amounts: 4 ounces of unprocessed red meat or poultry (about the size of a deck of cards), three ounces of fish, and, for processed meat, two slices of bacon, two small sausage links or one hot dog.
The participants were then followed for up to 30 years. The studies recorded how many of them developed cardiovascular disease, including fatal or non-fatal heart disease, heart failure or stroke (almost 7,000), as well as how many died from any cause (almost 8,900). Allen and her co-authors then looked for links between the rate sof cardiovascular disease and premature death from all causes and the participants’ meat consumption.
After adjusting for other factors known to be associated with cardiovascular disease and premature death, such as age, ethnicity, educational level, smoking, alcohol use, physical activity levels and overall dietary quality (such as the amount of fruit and vegetable consumed), the researchers calculated the following key findings:
- Eating two servings a week of processed meat or red meat increased the risk of cardiovascular disease by 3 percent to 7 percent. It also increased the risk of death from any cause by 3 percent. The longer the time frame, the higher the risk.
- Eating two servings a week of poultry increased the risk of cardiovascular disease by 4 percent, although the researchers note that the evidence isn’t strong enough to make a clear recommendation about poultry. The risk could be related to how the chicken is cooked and eaten, they point out. Fried chicken, for example, is generally considered less healthy than baked chicken.
- Eating fish was not associated with an increased risk of cardiovascular disease or early death.
Limitations and implications
All the studies used in the meta-analysis were observational (as were those used in last November’s study), which means their data doesn’t prove a connection between diet and cardiovascular disease or early death. In addition, the studies’ participants reported their eating habits only once. Their consumption of meat could have changed over time.
Self-reports of dietary choices also have another problem: They can be inaccurate.
So, although these findings are an interesting and important addition to the ongoing debate about meat’s potential risk to our health, they don’t end that dispute.
Yet they can’t be dismissed, either.
One thing is certain: Health officials aren’t likely to change their dietary recommendations for meat consumption any time soon. Those guidelines currently encourage the consumption of fresh fruits and vegetables, whole grains, legumes, fish, nuts and seeds, and recommend limiting the consumption of red and processed meats, refined grains, fried foods and sugar-sweetened beverages.
And if you’re worried about not getting enough protein, there are plenty of good sources other than meat.
“Fish, seafood and plant-based sources of protein such as nuts and legumes, including beans and peas, are excellent alternatives to meat and are underconsumed in the U.S.,” says Linda Van Horn, one of the study’s co-authors, in a released statement. In addition to being a professor of preventive medicine at Northwestern University, Van Horn is also a member of the advisory committee that has been working on the latest update of the U.S. Dietary Guidelines, which will be released later this year.
FMI: You’ll find an abstract of the study on the JAMA Internal Medicine website, but the full study is behind a paywall. The study was funded by the American Heart Association and the National Institutes of Health.