Is red meat healthy?
We have been told for decades that that eating red meat and processed meats contributes to heart disease and other medical problems. Now a new, and apparently reputable, metadata analysis has started a vigorous debate on the topic.
Here is what the two warring camps are saying:
Red Meat is Healthy
This is a statement from McMaster’s University as reported in Science Daily:
Contrary to previous advice, five new systematic reviews suggest that most people can continue to eat red and processed meat as they do now. The major studies have found cutting back has little impact on health.
Most people can continue to eat red and processed meat as they do now. A major study led by researchers at McMaster and Dalhousie universities has found cutting back has little impact on health.
A panel of international scientists systematically reviewed the evidence and have recommended that most adults should continue to eat their current levels of red and processed meat.
The researchers performed four systematic reviews focused on randomized controlled trials and observational studies looking at the impact of red meat and processed meat consumption on cardiometabolic and cancer outcomes.
In one review of 12 trials with 54,000 people, the researchers did not find statistically significant or an important association between meat consumption and the risk of heart disease, diabetes or cancer.
In three systematic reviews of cohort studies following millions of people, a very small reduction in risk among those who had three fewer servings of red or processed meat a week, but the association was uncertain.
McMaster professor Gordon Guyatt, chair of the guideline committee, said the research group with a panel of 14 members from seven countries used a rigorous systematic review methodology, and GRADE methods which rate the certainty of evidence for each outcome, to move from evidence to dietary recommendations to develop their guidelines.
Bradley Johnston, corresponding author on the reviews and guideline, said the research team realizes its work is contrary to many current nutritional guidelines.
“This is not just another study on red and processed meat, but a series of high quality systematic reviews resulting in recommendations we think are far more transparent, robust and reliable,” said Johnston, who is a part-time associate professor at McMaster and an associate professor of community health and epidemiology at Dalhousie.
Red Meat is Unhealthy
This is the outraged reply from Harvard T.H.Chan School of Public Health:
A controversial “dietary guidelines recommendation” published in Annals of Internal Medicine suggests that adults can continue to consume red meat and processed meat at current levels of intake.
This recommendation runs contradictory to the large body of evidence indicating 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. However, according to the Annals authors, their guidelines were based on a series of “rigorous” systematic reviews that would presumably account for all this available evidence.
Confused? We asked our experts to take a closer look at the research behind these guidelines. You can find the in-depth analysis below, but here are their key takeaways:
- The new guidelines are not justified as they contradict the evidence generated from their own meta-analyses. Among the five published systematic reviews, three meta-analyses basically confirmed previous findings on red meat and negative health effects.
- The publication of these studies and the meat guidelines in a major medical journal is unfortunate because following the new guidelines may potentially harm individuals’ health, public health, and planetary health. It may also harm the credibility of nutrition science and erode public trust in scientific research. In addition, it may lead to further misuse of systematic reviews and meta-analyses, which could ultimately result in further confusion among the general public and health professionals.
- This is a prime example where one must look beyond the headlines and abstract conclusions. It is important for journalists, health professionals, and researchers to look beyond the sensational headlines and even the abstracts of the papers to verify the evidence behind the claims. It’s also crucial to understand that nutrition research is a long and evolving process, and therefore critical to look at the totality of the evidence.
- These studies should not change current recommendations on healthy and balanced eating patterns for the prevention of chronic diseases. Existing recommendations are based on solid evidence from randomized controlled studies with cardiovascular risk factors as the outcomes, as well as long-term epidemiologic studies with cardiovascular disease, cancer, type 2 diabetes, and mortality as outcomes. To improve both human health and environmental sustainability, it is important to adopt dietary patterns that are high in healthy plant-based foods and relatively low in red and processed meats.
Push Back About the Study’s Methodology
Several knowledgeable scientists were so concerned by the new study’s recommendations that they wrote a letter to the journal attempting to prevent its publication. Some of these scientists criticized the study’s conclusions based on inappropriate methodology.
In reviewing this evidence, researchers writing the Annals papers relied on GRADE criteria. In an interview with MedPage Today, Christopher Gardner, PhD, of Stanford University, and co-signee of the response letter to the publication, explained that a “huge problem” with this assessment is how GRADE criteria is only suitable for drug studies, not nutrition studies.
Gardner also pointed out how only one of the panel’s five reviews included randomized trials, while the rest relied on observational epidemiologic data. Calling observational epidemiology “outdated,” he noted that this type of nutrition assessment misses the important question: “if they eat less meat, what do they eat more of … the health benefit of less meat is contingent on ‘what instead?’ which they don’t address.”
As for the one review including randomized trials, many of the trials were funded by the meat industry, and none looked solely at health outcomes from red and/or processed meats. Instead, most studies looked at outcomes of the Mediterranean diet. On the other hand, by far the largest trial included in this set and that drove the overall results as the government-sponsored Women’s Health Initiative.
Lead Researcher Apparently Has Ties to Food Industry
This is a recent report from the New York Times:
The lead researcher, Bradley C. Johnston, said he was not required to report his past relationship with a powerful industry trade group.
Several prominent nutrition scientists and health organizations criticized the study’s methods and findings. But Dr. Johnston and his colleagues defended the work, saying it relied on the highest standards of scientific evidence, and noted that the large team of investigators reported no conflicts of interest and conducted the review without outside funding.
Dr. Johnston also indicated on a disclosure form that he did not have any conflicts of interest to report during the past three years. But as recently as December 2016 he was the senior author on a similar study that tried to discredit international health guidelines advising people to eat less sugar. That study, which also appeared in the Annals of Internal Medicine, was paid for by the International Life Sciences Institute, or ILSI, an industry trade group largely supported by agribusiness, food and pharmaceutical companies and whose members have included McDonald’s, Coca-Cola, PepsiCo and Cargill, one of the largest beef processors in North America. The industry group, founded by a top Coca-Cola executive four decades ago, has long been accused by the World Health Organization and others of trying to undermine public health recommendations to advance the interests of its corporate members.
In an interview, Dr. Johnston said his past relationship with ILSI had no influence on the current research on meat recommendations. He said he did not report his past relationship with ILSI because the disclosure form asked only about potential conflicts within the past three years.
Critics of the meat study say that while Dr. Johnston may have technically complied with the letter of the disclosure rules, he did not comply with the spirit of financial disclosure.
“Journals require disclosure, and it is always better to disclose fully, if for no other reason than to stay out of trouble when the undisclosed conflicts are exposed,” said Marion Nestle, a professor of nutrition, food studies and public health at New York University who studies conflicts of interest in nutrition research. “Behind the scenes, ILSI works diligently on behalf of the food industry; it is a classic front group. Even if ILSI had nothing to do with the meat papers — and there is no evidence of which I am aware that it did — the previous paper suggests that Johnston is making a career of tearing down conventional nutrition wisdom.”
Dr. Christine Laine, editor in chief of the Annals of Internal Medicine, said the medical journal asks people to disclose their financial interests but relies on the integrity of the researcher and does not attempt to verify the forms. “We are really leaving it to the authors to disclose,” said Dr. Laine. “We advise authors if they wonder ‘Should I disclose this or not,’ they should err on the side of disclosure.”
My Advice About Eating Red Meat and Processed Meats
My first rule of healthy nutrition is to eat a balanced diet and that “everything in moderation” should be the touchstone. Use common sense and don’t get too excited by the latest sensationalist headlines about new studies and you’ll be on the right track. These types of yo-yo headlines and contradictory studies has dogged coffee and eggs for years.
Keep in mind that this current study is not based on any new research. Instead, it is merely the author’s take on what conclusions to draw from a series of prior studies. So here we have scientists arguing about what the appropriate standards to apply to analyze old research and coming to differing conclusions. Keep in mind that when researching nutrition it is never possible to establish a cause and effect relationship between eating a particular food and disease. There are simply too many other variables at play.
Also, it appears that the authors may be biased. I would definitely take that into consideration.
Here’s my advice: Eating red meat now and then will probably not cause any serious harm. I would focus on mostly eating lean proteins and fish and load up on fruits and vegetables. I haven’t eaten red meat since I was a teenager, but that’s mostly because it requires too much chewing. But, that’s just me!
Click here to read Annals of Internal Medicine original report on new study addressing the issue of whether red meat is healthy.