Meaty subjects have been in the news recently, with a series of studies questioning dietary recommendations that we eat less of the red stuff, even as plant-based substitutes have moved into the spotlight with fast-food breakthroughs. A new generation of faux burgers, such as Impossible Burgers and Beyond Meat, which more closely replicate the experience of eating the real thing (they even “bleed”), have been popping up on the menus of chains like Burger King, Subway, and KFC. Scientists re-examining the dietary role of red meat, meanwhile, turned the nation’s nutrition landscape on its head in early October by casting doubt on the conventional wisdom that generally Americans need to eat less of it. Those findings drew a rapid and negative reaction from several quarters, including the American Heart Association, the American Cancer Society, and scientists such as Frank Hu, chairman of the Nutrition Department at the Harvard T.H. Chan School of Public Health. Hu discussed the shifting landscape with the Gazette.
GAZETTE: Meat and meat substitutes have been prominent in discussions of diet and health recently. A group of scientists issued guidelines suggesting adults continue their consumption of red and processed meats — the opposite of existing recommendations to cut back. Can you help clear up the confusion?
HU: This was indeed very confusing, so I’ll get right to the point. The recent guidelines published in the Annals of Internal Medicine should not change existing recommendations on healthy and balanced eating patterns for the prevention of chronic diseases. Guidance to reduce red and processed meats is based on a large body of evidence indicating that higher consumption of red meat — especially processed red meat — is associated with higher risk of Type 2 diabetes, cardiovascular disease, certain types of cancers, and premature death. While this guidance is supported by both national and international organizations, including the American Heart Association, American Cancer Society, and the World Health Organization, consumers should know that the new guidelines were released by a self-selected panel of 14 members. Furthermore, when my colleagues and I closely reviewed the studies informing the panel’s decision, we saw that their findings contradicted their guidance. In short, the three meta-analyses of observational studies actually confirmed existing evidence on the potential for health benefits when cutting back on red and processed meats. However, because they based their analysis on a measure of three servings of red meat per week, the effects of an individual reducing consumption appeared small. But if you consider that about a third of U.S. adults eat one serving or more of red meat each day, the potential health benefits of reducing consumption become much greater.
GAZETTE: Authors of the new guidelines say that existing recommendations to cut back on red meat are based on “low-quality evidence.” How did they reach that conclusion?
HU: Looking at their methods, this is not surprising because they applied an assessment criteria to observational lifestyle research that was developed for evaluating clinical trials, such as those used in drug research. However, we can’t study diet the same way we can a pill. It would be unethical to select individuals and feed them high amounts of red meat over the course of many years to observe the outcome. For this reason, we need to look at research on diet in a more sophisticated way. Criteria have been developed and applied to do just that but the authors didn’t use them. The takeaway here is that nutrition research is complex, and rarely do [its findings] reverse so abruptly. That’s why it’s so important to look beyond the headlines at the quality of the evidence behind the claims. Still, the publication of these new guidelines in such a prominent medical journal is unfortunate as it risks further harm to the credibility of nutrition science, eroding public trust in research as well as the recommendations they ultimately inform.