If you caught any health news from The Washington Post, New York Times, or NPR this morning, you might have been inundated (happily or otherwise) with pictures of bacon, burgers, hot dogs, and sausages. And those pictures were likely accompanied by headlines touting new research that conflicts with nearly ubiquitous dietary advice to eat less red and processed meat.
The trouble is, this isn’t news at all—it’s just a terribly misguided interpretation of the evidence we already have. The new set of studies, published in a special issue of the Annals of Internal Medicine, has already drawn sharp criticism from a host of public health and nutrition experts, including leading researchers at Harvard, Stanford, and Tufts.
So let’s cut through the headlines.
Here’s the first thing to know: the new set of studies did not draw drastically different statistical conclusions from existing research. The studies reported that diets lower in red and processed meat are associated with reduced risk of all-cause mortality, type 2 diabetes, and multiple cardiovascular outcomes. We have applied similar findings in our own research, which found that if Americans reduced their intake of processed meat to just one serving per week, it might have saved 3,900 lives from colorectal cancer alone over the course of 2018.
But the authors of the new research took a wrong turn when they applied dubious research methods to grade the evidence as low-quality, and then concluded that the “minimal” health risks justify continued consumption of red and processed meat at current levels. This isn’t the first time that science has been twisted to dilute dietary recommendations, and it won’t be the last. But let’s head this one off at the pass.
When it comes to long-term health outcomes, observational studies are our best option
Why did the authors of this study call the current scientific evidence on red and processed meat “low-quality?” Largely because it derives from observational studies. An observational study is one that tracks a group of people (often called a “cohort”) over time to determine how certain risk factors may predispose individuals to develop a disease or condition. Like any study type, observational studies range in quality, but a well-designed study can produce robust and reliable results. Much of what we know about the role of nutrition in health and disease is derived from observational studies, in part because they allow researchers to look at decades of data and thousands of people’s behaviors—which is essential for assessing long-term health outcomes. (If I smoke today, I’ll likely be fine tomorrow, but if I smoke every day, will I be healthy in 20 years?)
Compare this to a “randomized controlled trial,” a study type that is often considered the gold standard of research. This is an experimental design that assigns a treatment or intervention to one group and compares them to another group that didn’t receive treatment. It typically allows researchers to tightly control for other variables that might otherwise influence the experiment outcomes, meaning they can be more confident about the results.
Some nutrition research can be accomplished through randomized controlled trials, including short-term diets or nutrition therapy for acute illnesses, but the applicability of the methodology is limited—and expensive. Yet that’s exactly what the authors of these studies are proposing: that we need higher quality nutrition research in the form of randomized controlled trials, and that other sources of information are dubious and unacceptable.
This would be great—if it weren’t nearly impossible.
Imagine telling one group of people to smoke a pack of cigarettes every day for the next 20 years to prove our hypothesis that cigarettes cause lung cancer. If it weren’t incredibly unethical (and it is), it would be a nightmare to track the same group of people for 20 years, let alone to ensure that they remained compliant with the treatment. It would take time and money that no research institution, anywhere, would be willing and able to dedicate. With any luck, future technology and methodological advances will one day make experimental approaches to studying diet and chronic disease possible. Until then, a well-designed observational study is our best option.
Health risks are only minimal until they happen to you
Our 2019 report, Delivering on the Dietary Guidelines, estimates the lives saved from preventing chronic disease by following science-based dietary recommendations. We based these projections on mortality data for the US population and current research on the relationships between diet and disease. In 2018, the National Cancer Institute estimated that more than 50,000 deaths were attributable to colorectal cancer—a disease that will affect about 4.2 percent of men and women over their lifetime. According to an abundance of data and research, that risk should decrease to about 3.5 percent in the absence of one 50-gram serving of processed meat per day.
A risk reduction from 4.2 percent to 3.5 percent might not sound like much—but when you’re talking about dietary patterns across a population, it adds up. Particularly if yours was one of the 3,900 lives that might have been saved by eating less processed meat last year. The point is this: protecting public health means providing recommendations based on the best available science, regardless of how valuable the perceived magnitude of risk is.
Author links to industry may raise questions
As reported by NPR, Dr. Bradley Johnston, the lead author of the paper that proposed the new guidelines, is no stranger to publishing controversial studies that contradict scientific consensus. In 2016, Dr. Johnston authored a study challenging recommendations to consume less than 10 percent of daily calories from added sugar. The basis of the challenge? “Low-quality” evidence.
Perhaps more concerning is that that particular study was funded by the International Life Sciences Institute (ILSI), an organization founded in 1978 by a Coca-Cola executive with a purpose of uniting the food industry. My colleague Derrick Jackson recently wrote about the web of industry interests ILSI represents, and how it attempts to influence official US dietary advice. Per a recent report from the journal Globalization and Health: “ILSI should be regarded as a lobby group and academics and researchers, policy makers, the media, and the public should view ILSI’s research as promoting the interests of the food, beverage, supplement and agrichemical industries, while its actions promote its members’ interests and counter healthy public policies.”
One author of the new studies examining the health outcomes of red and processed meat consumption also serves as an unpaid scientific advisor for both the Food, Nutrition, and Safety Program and the Technical Committee on Carbohydrates at ILSI North America. While one author’s past or current connections to industry does not warrant a dismissal of their research, the public should be aware of particular histories or relationships that could influence study results—especially when those results prove controversial.
These aren’t “new dietary guidelines”
The recommendations produced by these studies are not “new dietary guidelines.” They are one set of studies that have applied misconceived methodology to produce a new interpretation of the existing body of research. If the early response from public health and nutrition experts is any indication, this new research is unlikely to be taken seriously by the research community.
But it’s not the research community we should be most worried about. What is most worrisome about this research is that it has provided the general public with yet another headline portraying the field of nutrition science as a perpetual seesaw, with each new study reversing the conclusions of the last. I received three emails from family members this morning—all of whom have advanced degrees—asking me what to make of the latest research on meat. I’m concerned that the inherent value and trustworthiness of nutrition science itself is eroding in front of our eyes.
That’s why we have a Dietary Guidelines Advisory Committee that rigorously reviews scientific evidence on diets and nutrition every five years. Crucially, this committee concluded in 2015 that healthy dietary patterns are lower in red and processed meats. The process to develop our national dietary guidelines, which provides its full methodology and offers opportunity for public input, is what we should be paying attention to, and with the development of the 2020-2025 Dietary Guidelines for Americans underway, now is the perfect time to do it. Visit our website to learn more about UCS’s work promoting science-based dietary guidelines and to find out how to make your voice heard.
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