Cutting back on red and processed meat brings few if any health benefits, according to a Dalhousie University and McMaster University review of evidence drawn from millions of people. But the finding contradicts dietary advice of international agencies, and a decade of research, and has prompted criticism from many experts.
The researchers who conducted the review said their findings suggest most people can eat red and processed meat at current average intake, typically three or four times a week for adults in North America and Europe, without significant health risks.
However, experts from Harvard, Yale, Stanford and elsewhere, including one of the review authors, said guidelines that could lead people to eat more red and processed meats were irresponsible.
They asked in a letter to the journal that it “pre-emptively retract publication” of the papers pending further review.
A statement by the Harvard School of Public Health said: “From a public health point of view, it is irresponsible and unethical to issue dietary guidelines that are tantamount to promoting meat consumption, even if there is still some uncertainty about the strength of the evidence.”
The World Health Organization’s International Agency for Research on Cancer (IARC) and the World Cancer Research Fund (WCRF) both say red and processed meat may cause cancer.
The WCRF advises eating “little, if any” processed meat and only “moderate amounts” of red meat, such as beef, pork and lamb - with a weekly limit of 500 grams (17.6 ounces) cooked weight. The organization said that people should not misinterpret the review as saying meat is risk-free.
About the study
Led by researchers from Dalhousie and McMaster Universities, the study team performed five systematic reviews of previously published studies on red and processed meat and health. The findings were then used to craft intake guidance for consumers.
Among the randomized trials they selected for analysis, which included around 54,000 people, they found no statistically significant link between eating meat and the risk of heart disease, diabetes, or cancer.
Among the observational studies, which covered millions of people, they did find “a very small reduction in risk” in those who ate three fewer servings of red or processed meat a week, but said this association “was very uncertain.” These findings were ignored in the final intake recommendations because they were deemed low- or very-low quality by the grading method used to rate the evidence.
The authors’ concluding recommendation – that adults can continue eating red and processed meat at current levels – was based on their lack of confidence in their data. They acknowledged that their recommendation was weak.
Major health groups including the American Institute for Cancer Research, the American Heart Association, the American College of Cardiology and the Physicians Committee for Responsible Medicine pushed back quickly reiterating recommendations to limit red and processed meat and calling the recommendations “reckless” and a “major disservice to public health”.
Renowned nutrition researchers cited numerous criticisms, including the fact that major relevant studies linking significant cardiovascular benefits to eating less meat were omitted from the analyses.
The research results did not separate red meat from processed meat, suggesting that eating four servings of processed meat a week does not affect cancer risk, which isn’t supported by scientific evidence.
Experts also contend that while the methodology that was used to grade the studies is rigorous, it was developed for drug trials, not for observational studies on diet.
Leslie's bottom line
This new research is not a major scientific breakthrough. It does not change my advice to reduce intake of red and processed meat and to eat more protein from plants.
A large body of evidence exists to suggest that a high intake of red and processed meat increases the risk of ill health. I acknowledge that the risk on an individual level may be small, and that it’s your overall diet that matters most when it comes to health, not one food.
But it goes beyond human health.
Raising livestock and producing meat takes a large environmental toll affecting land degradation and water use, while releasing greenhouse gases and chemicals into the air and water.
Today, in my opinion, it’s narrow-minded to not consider environmental sustainability, as well as animal welfare, when making recommendations about meat intake.
Source: Annals of Internal Medicine, October 1, 2019.
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