Response from The Plantrician Project to the Annals of Internal Medicine Reviews on Dietary Meat Guidelines

The Annals of Internal Medicine systematic review and meta-analysis of red and processed meat titled “Unprocessed red meat and processed meat consumption: dietary guideline recommendations” draws inaccurate conclusions from a flawed design to advocate for the continued consumption of red and processed meat.  The conclusions stand in stark opposition to numerous trials and observational studies linking red and processed meat consumption with the increased risk for heart disease, stroke, some cancers, type 2 diabetes, and all-cause mortality.  Research from The World Health Organization conducted by 22 experts from 10 countries, reviewing more than 800 studies concluded that consuming 50 grams (1 hot dog or 3-4 strips of bacon) of processed meat daily increased the risk of colorectal cancer. The 2019 American College of Cardiology and American Heart Association guidelines based on a thorough review of the research recommend a diet that emphasizes the intake of vegetables, fruits, nuts, whole grains, and minimizes the intake of red and processed meats among other processed foods.  The NIH-AARP Diet and Health Study evaluated the diets of 536,969 people and concluded, “The results show increased risks of all-cause mortality and death due to nine different causes associated with both processed and unprocessed red meat, accounted for, in part, by heme iron and nitrate/nitrite from processed meat.”
 
 
These are a few examples, of many, from large studies that refute the findings of the Annals study. 
 
The study title and resultant sensational news headlines misrepresent the findings and fail to tell the story of the inherent limitations of this study and its meta-analyses methods.  Originally meta-analyses were utilized beginning in the mid-1970’s to summarize the data from studies of similar populations and identify trends, biases, or knowledge gaps and were inclusive.  However, error can enter into the final conclusions when the included studies are different in nature and or exclude other studies.  The Annals study discounted findings from multiple large American cohorts that are prospectively collected over a long period of time indicating harm from both red meat and processed red meat, predominately on the basis of the use of food frequency questionnaires, which they state, are inaccurate.  Other trusted guidelines like the ACC/AHA are based on multiple prospective observational cohorts including Adventist Health Studies (AHS-1 and -2), Nurses’ Health Study (NHS), Health Professional Follow-Up Study (HPFS), Atherosclerotic Risk in Communities (ARIC), National Health and Nutrition Examination Survey (NHANES), and the National Institute of Health-American Association of Retired People (NIH-AARP) study. These studies have a consistent signal of harm from processed and/or unprocessed red meat. In addition, if there were significant errors or inaccuracies adding noise to the data sets, it would be more difficult to achieve statistical significance in these studies, not less difficult.
 
Finally, we must avoid the reductionism that has marked our westernized approach to scientific questions and research.  Dietary recommendations should be simultaneously evaluated based on their impact to the global food web, or the seed to table journey, that includes soil and resource management and food/water access and availability.  Research from the largest study ever completed evaluated 38,700 farms from 119 countries and found that 80% of the farmland is utilized for farm animals to produce meat but produces only 18% of the calories and 37% of the protein.  Similarly, the EAT Lancet study brought together 37 experts in the intersection of health and global food sustainability for a population that will soon reach 10 billion.  Lead author Dr. Walter Willet said, “Transformation to healthy diets by 2050 will require substantial dietary shifts. Global consumption of fruits, vegetables, nuts and legumes will have to double, and consumption of foods such as red meat and sugar will have to be reduced by more than 50%. A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits.” These and other similar research studies concluded that a shift away from the consumption of animal products is necessary to preserve critical resources and feed a growing global population.
 
Dietary recommendations are more than a single meta-analysis or study and it would be foolish to disregard decades of research, both randomized control trials and observational data, linking red and processed meat to an increased risk of heart disease, stroke, type 2 diabetes, and some cancers.  We cannot allow an outlier study to undermine the tested recommendations that provide the greatest protection and prevention for populations around the world.  Finally, the food we eat and the way it is produced will have a lasting impact on the global resources that we will be leaving as an inheritance to our children and grandchildren.  Therefore it is imperative that we move beyond the gyrations imposed by a myopic view of a sensational headline study and regain focus through a careful review of the research and ongoing scientific dialogue about the impact of our diet on human health and global resources. 
 
Scott Stoll, MD FABPMR
Co-Founder The Plantrician Project