Where's The Beef? Embroiled In Scientific Controversy

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​Jen Thompson, MPP

“How do you know that spring is coming? Magazines start calling to ask if grilled meat causes cancer.” That was the “joke” we told each other in the National Cancer Institute’s press office – as predictable as the seasons themselves, we’d start getting calls in late winter from writers who wanted to know about the dangers of the backyard barbeque. Their questions were always similar -- do grilled meats cause cancer? How? Was meat healthier if it was cooked a different way? Did the type of meat matter? How much meat is “safe” to eat?  

The answers to these questions are complicated, and are even more so when telling people what they should and shouldn’t eat. Take, for example, a newly published set of dietary guidelines on red and processed meat.  Based on 4 systematic reviews – i.e., analyses of existing research – the Nutritional Recommendations (NutriRECS) Consortium drew the opposite conclusion than previous researchers and declared that “adults [can] continue current unprocessed red meat consumption (weak recommendation, low-certainty evidence). Similarly, the panel suggests adults continue current processed meat consumption (weak recommendation, low-certainty evidence).”

This recommendation was rejected by many prominent voices in nutritional epidemiology.  In its newsletter “The Nutrition Source”, the Harvard T.H. Chan School of Public Health made its opinion clear: “New “guidelines” say continue red meat consumption habits, but recommendations contradict evidence.”  Dr. Giota Mitrou, director of research at the World Cancer Research Fund, said “the message people need to hear is that we should be eating no more than three portions of red meat a week and avoiding processed meat altogether.” Journalists and other researchers asked if the guidelines were skewed by the NutriRECS Consortium’s relationship with the AgriLife Program at Texas A&M University, which “includes a beef cattle teaching program, educational workshops for cattle ranchers and promotion of Texas beef to consumers.” One of the study co-authors, Patrick Stover, is vice chancellor and dean of the AgriLife program, though he said the dietary guidelines on meat were completed before NutriRECS received any funding from AgriLife.  The lead author of the guidelines, Bradley C. Johnson, also authored a December 2016 study on sugar consumption, which was widely criticized due to its funding from the International Life Sciences Institute (ILSI), an industry-based group alleged to try to “undermine public health recommendations to advance the interests of its corporate members.”

What are the specific objections to these new guidelines? In the analysis published by the Harvard T.H. Chan School of Public Health, the author noted that the meta-analyses – the basis for the guidelines – found small but statistically significant associations between lower consumption of red and processed meats and lower total mortality, as well as cardiovascular disease (CVD) and cancer mortality, and decrease incidence of type 2 diabetes.  In other words, there is evidence that lower red and processed meat consumption may lower some health risks.  NutriRECS concluded that this evidence was too uncertain to justify recommendations that individuals change their current diets.

Nutrition experts have also criticized NutriRECS’ methodology, noting that their meta-analyses excluded several large and well-regarded studies of the DASH and Mediterranean diets because they were not specifically about meat consumption, and that the metric they used to evaluate previous studies, GRADE, is better suited to randomized controlled trials than to observational studies of nutrition.  Including these studies would have changed the results; using a different metric better suited to observational studies would have lent more certainty to their findings. Even the Consortium did not agree unanimously on the new guidelines – 3 of the 14 members voted for a recommendation to reduce red meat consumption.  

Where does this leave us with red and processed meat, and how much of it we should be eating? Well,  on average, Americans eat 222 pounds of meat per year, or about 9.75 ounces of meat per day.  That figure includes red and other types of meat, such as poultry; still, we already eat almost twice as much meat as the 5.5 ounce daily serving recommended by the American Heart Association.

​Another important factor, not considered by the NutriRECS guidelines, is the environmental impact of meat production. Researchers have estimated that 71% of the South American rainforests converted into farmland are used for cattle ranching; per calorie, meat produces more greenhouse gas emissions than plant-based foods.  As the global population grows and the demand for beef and other meats increases, maintaining our current levels of meat consumption is likely to be environmentally unsustainable.Many argue that it already is.  And while evidence of the health risks of meat consumption may be weaker than some scientists prefer, the health benefits of a diet that emphasizes plants and minimizes red meat are well known.  Personally, while I sometimes enjoy a steak or hamburger, I’m going to continue to save them for special occasions.