The recent article, “Unprocessed Red Meat and Processed Meat Consumption: Dietary Guideline Recommendations from the NutriRECS Consortium,” by B. Johnston, et.al., published Oct. 1 in the Annals of Internal Medicine certainly made a big splash in the news. The reason for the large media coverage is due to its literature review of red and unprocessed meat consumption and determining that meat’s association with death from cancer, heart disease or diabetes is low. This assessment has led to headlines proclaiming consumption of red and processed meat as safe.
Major health organizations and leading nutrition researchers have long recommended limiting red and processed meat consumption to reduce risk of these diseases. Why the controversy? Let’s assess how the new study was conducted and see where the differences arise.
What the Study Assessed
The study reviewed randomized and observational research of meat and processed meat consumption on cardiometabolic and cancer outcomes published through 2018. The authors only looked at studies of greater than 1,000 or more adults and those that ran 6 months or longer. They also looked at published research on the subjects’ health-related values and preferences related to this consumption. They decided 3 servings a week as a realistic reduction. They used GRADEpro software to rank the articles using a of panel of experts in health research, nutritional epidemiology, dietetics, family and internal medicine and three public members. However, they do not list the names of this panel nor credentials.
Acknowledged Study Limitations
Not widely covered in the media is some of the study limitations the authors discussed. They found most diet pattern studies did not typically report separate data for red and processed meat consumption. They also noted “other food and nutrient characteristics varied widely across studies.” They could not conduct any analysis of meat preparation differences, such as baking or boiling versus grilling or broiling — the latter are known to create cancer-causing heterocylic amines or HCAs, especially when the meat is charred. HCAs are chemicals that are formed when muscle meat like beef, chicken or pork is cooked using high temperature methods such as grilling. The authors also state they did not address the personal ethical preferences and the significant contribution meat production has on global warming.
Other Major Study Limitations
The study never defined what a serving of meat is. According to USDA’s MyPlate, 5-7 ounces of protein is needed daily, and the serving size for protein group foods is 1 ounce. Most registered dietitians define a typical portion size (amount of food you eat) from the protein group as 3 ounces. What people really consume at one time greatly varies, with restaurant portions of meat averaging 6-12 ounces. Besides not addressing meat preparation, no analysis was conducted on the cuts of meat, detailing the amount of saturated fat, sodium and calories. This is highly variable, especially in processed meats. For example, bacon and sausage have a high amount of saturated fat and sodium per serving, versus pork loin.
The study did not address the total diet composition of saturated fat, sodium, carbohydrates and food groups. Any registered dietitian can tell you the entire diet needs to be analyzed and compared to these disease risks, not one food. We don’t just eat one food or nutrient, so any realistic comparison to disease outcomes needs to take the whole diet approach. There are numerous randomized studies that show that following the Mediterranean diet and DASH (Dietary Approaches to Stop Hypertension) diet, for example, lowers blood pressure, LDL cholesterol, controls diabetes, and helps prevent and control heart disease, many cancers, obesity and other chronic diseases.
As discussed in the Dietary Guidelines for Americans, males aged 14-70 average an excess of 7-15 ounces above the recommended 23-31 ounces per week of lean meats, poultry and eggs, based on 1,800-2,600 kcal needs (Healthy US Style and Mediterranean Eating Patterns). The eating patterns of teen boys and men demonstrate the need for them to shift to consuming more seafood, and plant proteins and reduce animal protein intake, as recommended in the Dietary Guidelines for Americans. In this study, assessing a limit of 3 servings of red or processed meats a week is low for this group, and is a good goal. The article also incorrectly stated the Dietary Guidelines for Americans as recommending one serving of meat per week; it is one serving of lean meat, poultry, or eggs per day.
The study did not assess how much fish, nuts, seeds, soy products, low or high fat dairy or legumes as other protein sources were consumed. Americans are averaging one-half of what is recommended of these plant proteins and fish, especially for ages 14-30, and often meat is displacing these important heart-healthy foods. These amounts would also need to be assessed as a part of the total diet to determine cardiovascular risk and controlled.
It is interesting to note the authors took a population based approached to the study, yet directly noted their assessment is applicable to all individuals. Registered dietitians individualize diet recommendations based on medical diagnosis, medications, laboratory work, personal and cultural preferences. As noted above, certain sex and age groups overconsume meat, poultry and eggs, for example and have varying caloric needs. Lumping all ages and sexes together in this analysis and making a blanket meat consumption safety recommendation cannot be valid for all.
The study curiously excluded research of less than 1,000 subjects per study, and those less than 6 months in duration. There is no explanation why. This excludes a large amount of studies from their analysis, so makes it incomplete. It also lumps together large observational studies, with cannot assess cause and effect, with randomized controlled studies.
In a major review article or any published research, the reader needs to consider any potential conflict of interest by the authors. In the authors’ disclosure they did not report accepting money from the meat industry, as reported by New York Times and Healthline. The study was funded by the International Life Sciences Institute, an industry trade group. These facts and their nondisclosure make the entire analysis more suspect and potentially biased.
In summary, there is good reason the American Heart Association, American Cancer Society, American Institute for Cancer Research, researchers from the Harvard T.H. Chan School of Public Health, and registered dietitians have complained about this review study and its significant limitations. Following the Mediterranean, DASH, and Healthy US Style Eating Patterns as recommended by these leading health organizations and nutrition professionals is still a valid, research and evidenced based good idea. Contact a registered dietitian for a more individualized eating plan and diet recommendations.