John Sharp didn’t mince words when he fired off an angry letter to Harvard University’s president back in January. The chancellor of the Texas A&M University system wrote to decry the actions of Harvard nutrition scientists who had publicly maligned Texas A&M AgriLife—the university’s agricultural college and four state research agencies—as part of a “disinformation triangle” beholden to the beef industry. “I can assure you that Texas A&M’s research is driven by science. Period,” wrote Sharp, sharply.
At issue was a controversial report, published last fall in the Annals of Internal Medicine, that argued to upend the dietary recommendations resulting from a scientific consensus linking red meat to heart disease and cancer. Its lead author, Bradley Johnston, had received funding for other work from AgriLife and has since joined A&M as an associate professor, and AgriLife vice chancellor Patrick Stover was among his eighteen co-authors. Because AgriLife accepts money from the beef industry, the critics implied, the motives of any researcher it funds are suspect. (These same critics quickly dismiss suggestions that their own funding by makers of plant-based foods influences their research.)
This chorus of name-calling has put Texas A&M at the center of a decades-long debate over the proper role of red meat in a healthy diet and likely left many Texans more confused than ever.
It’s a scenario that has played out again and again. Eggs were bad for you, then good again. Butter, wine, chocolate, coffee—all have been alternately touted for their benefits and disparaged for their potential harm. Fat, which most red meat features in abundance, was once considered public enemy number one, but that prompted the processed food industry in the eighties and nineties to create many low-fat products loaded up with sugars instead (to make up for their relative lack of flavor). What followed was an epidemic of obesity and Type 2 diabetes, for which experts now point to an overindulgence in simple carbohydrates—thanks to all those added sugars—as a significant cause. That, in turn, spurred the growing popularity of meat-heavy, low-carb diets that often yield impressive weight loss but about whose long-term effects many nutritionists still worry.
The irony of the latest controversy is that the Annals report wasn’t even based on some groundbreaking new study; it was an analysis of the quality of previous studies. The authors concluded that the existing research showed only a “trivial” risk associated with eating red meat—and not enough to justify the major dietary guidelines that recommend Americans cut back on how much of it they eat. Critics of the research, including Frank Hu and Walter Willett at Harvard, called that conclusion outright wrong. The link between meat and a host of serious health problems, from diabetes to cancer, they said, is statistically significant—in the same ballpark as the link between taking statins and lowering cholesterol. No one seems to question the efficacy of taking statins, so why question that of limiting meat consumption?
The truth is, it is difficult to know anything for sure when you’re attempting to determine the effects of just one dietary element, such as red meat. There are a vast number of potentially confounding variables to consider—primarily all the other foods and drinks and drugs consumed by the subjects of a study, but also how the food was prepared, participants’ exercise habits, their genetic predispositions, and environmental factors such as air and water quality.
To truly establish cause and effect between eating red meat and long-term outcomes such as cancer or heart disease, you’d need randomized controlled trials. Only, for practical purposes, that’s impossible. Doing so would require researchers to control every bit of food and drink each subject consumes for decades. That’s why much of what we’ve learned about nutrition and its effects on health has been drawn from observational studies—the diets and health outcomes of thousands of subjects monitored over years. Usually dependent on self-reporting by participants about what they’ve had to eat and drink, observational studies are inevitably imperfect because of faulty memories and the lack of full disclosure. Still, such studies are viewed by most nutrition experts as the best source available for sussing out long-term effects. And when it comes to red meat, the available data mostly point in the same direction: namely, the more red meat you eat, the greater your risk of contracting heart disease or cancer.
The Annals report didn’t dispute that correlation. But, the authors argued, it’s worth drilling into what levels of increased risk we’re talking about. For instance, by synthesizing the findings of earlier studies, the Annals review found that eating three fewer servings of red meat per week (Americans average 4.5 servings) reduced study participants’ risk of dying from cancer by 7 percent. Yet that effect looks much smaller when you consider the reduction in absolute terms. A person who cut out three servings per week saw his or her lifetime chance of dying from cancer fall by less than one percentage point, from 10.5 percent to 9.8 percent. Similar statistics held for heart disease. In those terms, it might hardly seem worth giving up red meat if you enjoy it. (It’s worth noting, however, that the Annals authors explicitly acknowledged legitimate environmental and animal-welfare concerns as reasons for limiting consumption of red meat.)
From a public-health perspective, if a million Americans cut back on their red meat by three servings per week, the small drop in each individual’s risk would translate to seven thousand fewer people dying of cancer. Expand that effect to the entire American population and more than two million would at least live somewhat longer, healthier lives—not to mention millions more potentially spared a premature death from heart disease. That’s enough preventable disease to affect the cost of health care for everyone who pays taxes and buys insurance—so even the most cynical reading of the data supports the USDA’s recommendation to moderate red-meat consumption.
Red meat is more consistently associated with negative health outcomes than poultry and fish. Whether some kinds of beef are less risky than others is unclear. There’s no convincing evidence, for instance, that beef from grass-fed, pasture-raised cattle is any better for you than that from corn-fed cattle on large-scale industrial farms. (Though most nutrition scientists suspect what common sense would suggest—that we’re better off avoiding meat from animals injected with hormones and antibiotics.) Dietitians generally advise eating the leanest possible cuts and varieties, including those raised on grass rather than grain. But lean meats contain more cholesterol per ounce than the fattier bits, so even that advice isn’t a sure thing.
USDA guidelines lump red meat into the same category as poultry and eggs, so it can be difficult for Americans to know how much red meat they should allow themselves from among the 26 ounces of meat and eggs per week the USDA suggests. Harvard’s Willett recommends eating no more than about one ounce of red meat per day—or one big, juicy hamburger’s worth per week. A&M’s Stover, on the other hand, maintains that diners are fine to continue eating whatever amount of red meat they currently do. He enjoys three to five servings per week.
Marissa Epstein, the director of the University of Texas Nutrition Institute, offers another way to think about how much meat to eat. Keep in mind, she says, that every bit of meat piled on a plate means less room for plants, which all the major dietary guidelines point to as the centerpiece of healthy diets. Epstein also believes we needn’t limit our dietary decisions solely to weighing nutritional data. “There are a lot of people who would say don’t eat red meat at all,” she says. “But food isn’t just about nutrition. It’s here to provide community. It’s part of our Texas culture. We have access to some of the most amazing food, and if we just eat a little bit less red meat, we’re all going to benefit from that, and we still don’t have to sacrifice enjoying meals with people we love.”