A new clinical guideline about red and processed meat has recently surfaced and captured mainstream media’s attention because of its overall conclusion: Past findings are wrong.
The guideline, Unprocessed Red Meat and Processed Meat Consumption: Dietary Guideline Recommendations From the Nutritional Recommendations (NutriRecs) Consortium, suggested that consumption of red and processed meats does not negatively impact health and should continue as normal. However, the guideline has generated controversy since it was published in early October, with some sources saying the guideline was not accurately conducted.
Guideline recommendation
NutriRecs is an “independent group with clinical, nutritional and public health content expertise, skilled in the methodology of systematic reviews and practice guidelines.” The group states it is not hampered by institutional constraints and conflicts of interest, and strives to produce trustworthy recommendations based on values, attitudes and preferences of patients and community members.
The guideline was voted on by a panel of 14 members from seven countries. Considerations of environmental impact or animal welfare were not factors in the guideline. Four systematic reviews looked at the health effects associated with red meat and processed meat consumption, and an additional review addressed people’s health-related values and preferences regarding meat consumption.
The guideline’s conclusion recommended that adults continue current unprocessed red meat consumption—which was given at a weak recommendation with low-certainty evidence—as well as continue current processed meat consumption—also with a weak recommendation with low-certainty evidence.
The guideline states that contemporary guidelines typically recommend limiting consumption of unprocessed red meat and processed meat.
The 2015-2020 Dietary Guidelines for Americans recommend limiting red meat intake, including processed meat, to approximately one weekly serving. The World Health Organization International Agency for Research on Cancer claims consumption of red meat is “probably carcinogenic” to humans, whereas processed meat is considered “carcinogenic” to humans.
The NutriRecs guideline argues however, that these recommendations are based on observational studies that are at “high risk for confounding” and are therefore limited in establishing “casual inferences” and do not report the absolute magnitude of any possible effect.
The guideline also states, “The organizations that produce guidelines did not conduct or access rigorous systematic reviews of the evidence, were limited in addressing conflicts of interest, and did not explicitly address population values and preferences, raising questions regarding adherence to guideline standards for trustworthiness.”
The guideline suggests the solution for the limitations of contemporary nutrition guidelines is for an independent group to provide recommendations based on values and preferences of guideline users. Enter, the development of the NutriRecs group to produce recommendations.
Methodology
The sample demographic for the guideline was individuals who consume red meat or processed meat as part of their diet. NutriRecs conducted a series of systematic reviews assessing the following questions: What is the effect of diets and dietary patterns lower in red or processed meat versus diets higher in red or processed meat; and what are individuals’ health-related values and preferences for red and processed meat consumption.
The group hypothesized that if red meat and processed meat consumption were related to adverse health outcomes, there would be stronger associations in studies that specifically addressed red meat and processed meat intake, versus studies addressing dietary patterns.
The guideline was formed after NutriRecs conducted a review of randomized trials on harms and benefits, with 12 trials enrolling 54,000 participants. The randomized trials found low- to very low-certainty evidence that diets lower in unprocessed red meat may have little or no effect on the risk for major negative outcomes.
NutriRecs also conducted meta-analyses of 40 studies with 3.6 million participants, which the group claimed there was low- to very low-certainty evidence that decreasing consumption may result in a very small reduction in the risk for major negative outcomes such as diabetes, cancer or cardiovascular disease.
NutriRecs also summarized people’s attitudes on eating meat, and found that in general, omnivores enjoy eating meat and find it to be an essential component of a healthy diet.
“In our assessment of causal inferences on unprocessed red meat and processed meat and adverse health outcomes, we found that the absolute effect estimates for red meat and processed meat intake were smaller than those from dietary pattern estimates, indicating that meat consumption is unlikely to be a causal factor of adverse health outcomes,” the guideline summarized.
NutriRecs recommends current consumption of red and processed meat should continue as is, because the certainty of evidence for potential negative health outcomes associated with meat consumption was low to very low. The guideline also states that if the very small exposure effect is true, given people’s attachment to their meat-based diet, the associated risk reduction is not enough to provide motivation to reduce meat consumption.
The guideline concludes, “What is certain is that generating higher-quality evidence regarding the magnitude of any causal effect of meat consumption on health outcomes will test the ingenuity and imagination of health science investigators.”
Backlash
Before its October release in the scientific journal, Annals of Internal Medicine, the guideline garnished significant backlash from health professionals and organizations.
A group of health researchers and professionals wrote a letter to the journal in late September before the guideline was published, requesting the guideline be retracted on the basis of “grave concerns about the potential for damage to public understanding and public health.”
The group is comprised of 14 individuals, including researchers at Stanford University, Harvard University, and University of Toronto, and industry professionals at the True Health Initiative and American College of Cardiology.
The group noted that the “allegedly ‘systematic’ reviews in this cluster omitted prominent trials that appear to satisfy fully the stated inclusion criteria” and NutriRecs overlooked information provided in studies that consistently show patterns of harm and adverse health effects.
“That the authors contend ‘very low certainty’ in their own findings is in no way a logical or even rational basis to recommend…the opposite,” the letter read and continued, “This is, simply, an overt misrepresentation. Such distortion is a direct threat to public understanding, and public health.”
The letter also noted that one of the signatories on the letter is one of the NutriRecs study authors, who also disagrees with the conclusions and guidance of the guideline.
The group ultimately requested for withholding of the “publication of potentially damaging misinformation.”
The guideline was published on Oct. 1.
In addition to the letter sent by the group of industry professionals, the World Cancer Research Fund International (WCRF) produced a statement disavowing the guideline.
“The public could be put at risk if they interpret this new recommendation to mean they can continue eating as much red and processed meat as they like without increasing their risk of cancer,” said Giota Mitrou, director of research at WCRF. “However, this is not the case. The message people need to hear is that we should be eating no more than three portions of red meat a week and eat little, if any, processed meat. We stand by our rigorous research of the last 30 years and urge the public to follow the current recommendations on red and processed meat.” — Anna Miller, WLJ editor
