Welcome to the Great Debates, where we consider the greatest nutritional controversies of our time. Our goal isn't to tell you what to think or do, but rather to present both sides of hot-button issues, like coffee (is it good for you?) and breakfast (the most important meal of the day?). What's being said? Who's saying it? Then it's up to you to make your own decisions.
If you are looking for evidence that red meat is killing you, there is no shortage of cautionary headlines. Here's a brief, incomplete sampling: "Red Alert on Red Meat" (Time, 2001); "Dying for Some Red Meat? You May Be" (Washington Post, 2009); "Red Meat Linked to Cancer and Heart Disease" (New York Times, 2012); "Meat Is Linked to Higher Cancer Risk, W.H.O. Report Finds" (New York Times, 2015); "Eating too much red meat 'can age the body', researchers claim" (The Guardian, 2016); Red Meat Tied to Diverticulitis Risk (New York Times, 2017).
We could do this all day!
And yet there is a wrinkle, which is that plenty of other studies suggest red meat not only won't kill you, but may in fact even be good for you. A 2012 study in the American Journal of Clinical Nutrition showed that eating lean beef might actually reduce the risk of heart disease. Multiple studies have shown meaty, Atkins-like diets to be particularly effective for weight loss. And then there are the various health benefits of saturated animal fats.
There is enough conflicting (and muddled, and often flawed) evidence to leave a person very confused, and also hungry. Should we foreswear our organic, grass-fed hamburgers? Should we eat more hamburgers? Are we eating just the right number of hamburgers? Does it even matter at all?
In the interest of both taste and longevity, let us examine the evidence.
The Case Against Red Meat
Red Meat and Cancer
A 2012 analysis showed red meat consumption to be "associated with a sharply increased risk of death from cancer and heart disease," the Times reported — and the more red meat you eat, the study found, the greater the risk. The risk of non-specific "cancer," for example, went up 10 percent for each daily three-ounce increase of red meat. "When you have these numbers in front of you, it's pretty staggering," the study's lead author, Harvard professor Frank B. Hu, told the Times.
Other studies have suggested possible, if sometimes tenuous, correlations between red meat and breast cancer, red meat and stomach cancer, and red meat and pancreatic cancer. But perhaps the cancer most associated with red meat is colon cancer.
"The less red meat the better," Dr. Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health, told Time in 2001. "At most, it should be eaten only occasionally. And it may be maximally effective not to eat red meat at all." Willett's study, first published in The New England Journal of Medicine, showed that women who ate lamb, beef, or pork every day as a main dish were two-and-a-half times more likely to develop colon cancer than their less carnivorous peers.
And that's certainly not the only study to draw a link between red meat and colon cancer: A 2015 grand meta-analysis of 10 different meta-analyses, all looking at the link between red meat and colon cancer, ultimately concluded that "red meat and processed meat convincingly increases [colorectal cancer] risk by 20 to 30 percent."
The same year, the World Health Organization announced their verdict: They'd found "sufficient evidence" that eating processed meats (your ham, your bacon, your hot dogs) could increase the risk of colon cancer. The WHO panel's conclusion for unprocessed red meat was less definitive: It's "probably" carcinogenic based on "limited evidence."
Red Meat and Heart Disease
But it was concerns about the link between red meat and heart disease that put red meat under the microscope in the first place. At Thrillist, Jody Berger lays out the history, but the short version is this: In the 1950s, a physiologist at the University of Minnesota named Ansel Keys noticed that American businessmen — who, by virtue of wealth and of circumstance, could eat pretty much anything they wanted, any time they wanted it — were getting a lot of coronary heart disease, but their European counterparts weren't.
He and his team embarked upon the landmark Seven Countries Study, which tried to understand the possible links between diet and heart disease, and found that men in Italy and Greece were eating a lot less red meat than their American peers, and also seemed to have much lower rates of heart disease.
While the study did not show that not eating red meat was responsible for not getting heart disease — it showed correlation, not causation — the idea stuck. And although subsequent studies have not disproved the link, they also haven't come to definitively damning conclusions.
Still, a 2009 longitudinal study, which followed more than half a million people over the age of 50 for 10 years, found that people who ate the most red meat (beef, lamb, and pork, for their purposes), were 30 percent more likely to die from "heart disease or any type of cancer." And that 2012 study out of Harvard — the same one that that suggested a link between red meat and cancer — seemed similarly pessimistic about the lasting heart health of devoted carnivores. It showed that the risk of "cardiovascular death" went up by 16 percent for each daily three-ounce increase of red meat — and 21 percent, if we're talking about processed meats in particular.
Then again, another meta-analyses of several studies in 2013 found that people who regularly eat unprocessed red meat had only a slightly higher heart disease risk than their chicken- and fish-loving peers.
But the plot thickens: A 2013 study from the Cleveland Clinic, suggested that while yes, red meat may be (somewhat) harmful, it's not necessarily for the reasons people think. The primary issue, the scientists found, might not have to do with saturated fat, or cholesterol, or even necessarily the troublesome carcinogens released when meat is cooked.
Instead, it has to do with L-carnitine, a compound abundant in red meat. As the Harvard Health Blog explains, gut bacteria digest L-carnitine and turn it into something called trimethylamine-N-oxide (TMAO). And in mice, TMAO has been shown to cause atherosclerosis, the "disease process" that kicks off cholesterol-clogged arteries. And that can lead to heart attacks. The researchers weren't able to show a similarly causal relationship in humans, but they did find that TMAO levels predicted heart attack risk.
The Case Against the Case Against Red Meat
Red Meat and Correlation — Not Causality
The problem with almost all of these studies, however, is that they show correlation, but they don't show causality. Which makes sense! To do a controlled experiment, you'd have to have people agree to stay on prescribed diets (that may or may not kill them). Strictly. For years.
As a result, we're left with a whole lot of observational data. That's not nothing, but it's also not conclusive. We have two points, but we don't have a connection between them.
On his blog, author Gary Taubes — a self-proclaimed carnivore, it's worth noting — walks through the issue, using Willett's Harvard study as his example. Using an enormous data set, that study showed women who ate a lot of red meat were the most likely to develop colon cancer, while women who ate basically no red meat were the least.
What do we actually learn from this, though? Not that much. The problem, Taubes writes, is that "as we move from the bottom quintile of meat-eaters (those who are effectively vegetarians) to the top quintile of meat-eaters we see an increase in virtually every accepted unhealthy behavior — smoking goes up, drinking goes up, sedentary behavior (or lack of physical activity) goes up." BMI also goes up, blood pressure rises and so on.
There are a ton of factors that cluster together, and some of them, or one of them, or many of them — who knows? — leads to a poor result: colon cancer. But by its very nature, the study can't definitively say the culprit is the meat.
And there's another wrinkle, Taubes points out: given the decades of anti-red meat nutritional wisdom, it makes sense that people who abstain from red meat would be healthier — they're following directions! They're probably health-conscious and follow other healthy directions, too!
More evidence that these sorts of studies are tricky? In the New York Times, Aaron E. Carroll points to a 2012 systematic review "that pretty much showed that everything we eat is associated with both higher and lower rates of cancer." Excellent! (Or terrifying?)
Red Meat and Improved Heart Health
There are also studies that suggest a diet high in red meat may actually be beneficial. A study out of Stanford comparing four different weight-loss diets followed about 300 overweight or obese women for a year. The women who saw the biggest drops in BMI, triglycerides, and blood pressure (all heart-healthy things)? The women who were randomized to "the Atkins-like meat- and bacon-heavy diet," Taubes notes with glee.
And a (tiny) 2012 study published in the American Journal of Clinical Nutrition found that eating lean beef actually improved cholesterol levels and decreased the risk of heart disease — in their sample, eating more beef had better outcomes than eating less beef.
Red Meat and Iron, Protein, and Vitamins
Studies aside, red meat is not without nutritional benefits to counter the potential downside: It's high in iron (and not just any iron, but heme iron, which, the Telegraph explains, is "absorbed faster and put to work more efficiently" than the kind in leafy greens); it's got tons of protein; and it's full of easy-to-absorb vitamins.
Also, it's got saturated fat — and, despite what a lot of us were told for years, that's a good thing. Greatist breaks it down: Saturated fat helps keep the liver healthy, boosts immunity, and has a positive effect on hormones.
In Conclusion, Practice Moderation
So what should you take away after all of this? There is a lot we don't know about red meat. There is a lot we don't know about nutrition in general, largely because of the difficulty to conduct definitive studies.
Here's what we definitely know for sure: When it comes to adopting a healthy diet you'll stick to, moderation tends to work better than deprivation.
Also, if given the choice between a grass-fed steak and a processed hot dog, go with the steak — a tragedy, we know.
Have your own thoughts marinating on the matter? Let us hear them.