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By: Adaora Ntukogu
Red and Processed Meat Not So Bad?
The Annals of Internal Medicine recently published the results of a study that looked at the consumption of red and processed meat and the risk for heart disease and cancer. In it, the authors suggested that there is no need to cut back on red and processed meat.[1] Robin W.M. Vernooij, a postdoc researcher specializing in Nephrology and Urology, and colleagues concluded that the evidence suggesting processed and red meat consumption can have adverse cardiometabolic and cancer outcomes are low in certainty.
These results are very controversial because it challenges the American Heart Association and American Cancer Society’s recommendations to limit the intake of these foods. Many nutrition experts are unsettled because this conclusion contradicts a large body of evidence arguing the opposite. Decades of observational studies have established that people who consume less red and processed meat, over time, have lower rates of heart disease and death from certain cancers. The World Cancer Research Fund advises individuals who consume red meat to limit their consumption to no more than about three portions per week and to consume very little to no processed meat. The World Health Organization has classified processed meat as carcinogenic to humans and has defined it as a major contributor to colorectal cancer. Further, in the Journal of Internal Medicine, Alicja Wolk published findings of an increased risk of prostate cancer, pancreatic cancer, and overall cancer mortality with the daily consumption of processed meat.[2]
The authors of the study published in Annals have received plenty of backlash from other nutritionists and health experts for their down-play of the negative health effects associated with red and processed meat consumption. NBC News Health and Nutrition Editor Madelyn Fernstrom, asserted that advising people to eat meat at their current rate was not the right recommendation and what should have been recommended was “limiting [intake] to three servings or less a week”. Dr. Frank Hu, the chair of nutrition at Harvard T.H. Chan School of Public Health suggests that “[i]f the same procedure were used to validate secondhand smoking…the evidence would be rated very low or low quality.”
On a search to garner the opinions of other health professionals on this matter, I was fortunate to find one nearby. I interviewed world renowned nutritionist, Dr. Dan Benardot, who is currently a Professor of Practice at the Center for the Study of Human Health. Dr. Benardot is the inventor of NutriTiming® web-based and Apple iOS software, which provides advice on energy balance to improve body composition and athletic performance. He is the author of several books, including Advanced Sports Nutrition-2nd Edition and Nutrition for Exercise Science, which was published this year. Dr. Benardot has worked for many years with several Olympic athletes, including power athletes, endurance athletes, gymnasts, and figure skaters. He was also the Atlanta Falcons team nutritionist for the 5 years leading up to their 2017 NFC Championship, to name a few accomplishments.
And Dr. Benardot had several thoughts about these unusual findings, which can be grouped into two main observations.
1. “They Created a Meta-analysis of Good Science Versus Bad Science”
Dr. Benardot first discussed the technique the author’s used to come to these conclusions, arguing that it may not be the best approach given the topic of nutrition.
The authors of the study in Annals say that they are not convinced by the studies that link red and processed meat to adverse health risks. They conclude that the existing guidelines from leading health groups to limit red and processed meat are based on “low-certainty evidence.” How did they conclude this?
The authors used GRADE, a systematic approach used to rate the quality of scientific evidence. Using this approach, a kind of study known as a randomized controlled trial is considered high-quality evidence, but this type of study design is not feasible for nutritional studies. “In nutrition, you really need to have observational studies, which in their analyses are not as high quality”, Dr. Benardot says.
Benardot believes that the author’s approach is best for drug research, which relies heavily on randomized control trials that would have been rated high on the GRADE scale for quality evidence. Most nutritional research is observational because it is unethical to ask people to change their diets to the magnitude necessary for a randomized controlled trial.
2. “This Study Could Be Misleading”
Dr. Benardot believes that what was published could be extremely misleading to the public. Observational studies are useful because we need to observe how people are eating and put it into context to get a better picture.
“It’s not just do you eat red and/or processed meat, it is how much you are eating at once, what you are eating it with, how it is prepared”, Dr. Benardot says. All of these variables are critically important to understand what the effects of eating red and processed meat might be.
He gives an example of Person A who eats a huge New York strip steak with french fries, a salad loaded with oil and vinegar dressing, and a side of vegetables covered in a thick sauce. That is a huge fat intake all at once. The health problems may be attributed to the meat, but it is the entirety of the dish that has caused the problem. Person B has exactly the same amount of fat but has spread it out over the course of a few days and may not have nearly the health problems of Person A.
The health issues that humans face with fats and other foods like processed and red meat are time-mediated and context dependent, something a randomized control experimental study cannot capture. By failing to take into account how nutritional studies work, Robin W.M. Vernooij and colleagues have eliminated some important studies that have discussed the effects of the consumption of these foods. Their study results may have influenced others to negate the decades of research highlighting the association of red and processed meat and chronic illnesses. This is dangerous because people who have previously been making a conscious effort to reduce red and processed meat intake, may have taken a halt. However, an important lesson has come out of the critiques of the Annals study. It is important for people to be able to look beyond the headlines and the abstract conclusions to verify and critique the evidence behind the claims.
References
1. Vernooij, R., Zeraatkar, D., Han, M., El Dib, R., Zworth, M., Milio, K., . . . Johnston, B. (2019). Patterns of Red and Processed Meat Consumption and Risk for Cardiometabolic and Cancer Outcomes: A Systematic Review and Meta-analysis of Cohort Studies. Annals of Internal Medicine, Annals of internal medicine, 01 October 2019.
2. Wolk, A (2017). Potential health hazards of eating red meat (Review). J Intern Med, 281, 106— 122.
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