There are no health reasons to cut down on eating red or processed meat, according to a new review of the evidence. The claims, which contradict most existing dietary advice, come from a review of existing studies led by the Spanish and Polish Cochrane Centers, part of a global collaboration for assessing medical research.
Numerous health bodies have said for decades that we should limit our intake of red meat because it is high in saturated fat, thought to raise cholesterol levels and cause heart attacks. More recently, both red and processed meat have been linked with cancer.
In the latest review, though, the authors came to a different conclusion because they considered separately the two main kinds of research. The best evidence comes from randomised trials. In these, some participants are helped to change their diet in a certain way, such as eating less meat, and the rest aren’t. At the end, the health of the people in the two groups is compared.
But such trials are costly and hard to do. According to one estimate, only about 5 per cent of nutrition studies are large, good-quality randomised trials. It is much more common to do research that just observes what people choose to eat undirected. Known as observational studies, these are notoriously open to bias and can give misleading results.
Bradley Johnston of Dalhousie University in Halifax, Canada, and his colleagues first reviewed all previous observational studies looking at the health impact of eating red or processed meat. These pointed to a “very small” adverse effect on deaths, heart disease and cancer.
Then they separately reviewed the 12 randomised trials that have been done in this area, and found that there was little or no health benefit for people who cut down on eating these meats. Based on these findings, the authors conclude that people should “continue to eat their current levels of red and processed meat unless they felt inclined to change them themselves”. However, they added that some might want to change their diet because of animal welfare or environmental reasons.
“It may be time to stop producing observational research in this area,” Tiffany Doherty from Indiana University’s Pediatric and Adolescent Comparative Effectiveness Research team wrote in an accompanying editorial.
Duane Mellor, a spokesperson for the British Dietetic Association, says people shouldn’t take the advice as a green light to eat more red meat. “What it doesn’t say is that we can tear up the guidelines and start eating twice as much meat. But red meat three times a week is not a problem.”
Journal reference: Annals of Internal Medicine, DOI: 10.7326/M19-1621
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