Is eating red meat linked to cancer and heart disease, but are the risks large enough to justify giving up juicy hamburgers and juicy steaks?
Probably not, according to researchers who reviewed data from 12 clinical trials involving about 54,000 people. In a series of controversial articles, the researchers argue that the increased health risks associated with red meat are small and uncertain, and that hack probably wouldn't be worth it for people who like meat.
That conclusions, which appear in the Tuesday edition of the Annals of Internal Medicine, go against established medical advice. They were quickly attacked by a group of prominent US scientists who took the unusual step of trying to prevent newspapers from being published until their criticisms were addressed.
The new work does not say that red meat and processed meats, such as hot dogs and bacon, are healthy, or that people should eat more. Previous study team analyzes often support ties with cancer, heart disease, and other poor health outcomes.
But the authors say the evidence is weak and there is little certainty that meat is really to blame, as other dietary and lifestyle factors may be at play.
Most people who understand the magnitude of the risks would say, "Thank you, but I will continue to eat my meat," he said. Dr. Gordon Guyatt from McMaster University in Canada, member of the international research team that conducted the reviews.
It is the latest example of how split nutritional research has become, with its uncertainties leaving the door open for conflicting advice. Critics say the findings are usually not backed by strong evidence. Advocates argue that nutritional studies can rarely be conclusive because of the difficulty of measuring the effects of any food, but these methods have improved.
"What we need to do is analyze the weight of the evidence – that's what the courts use," he said. Dr. Walter Willett, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health, who was among those who called for the postponement of newspaper publication.
Willett, who has led studies linking meat to poor health outcomes, also said the analyzes did not consider the particularly pronounced benefits of switching from red meat to vegetarian options.
Annals of Internal Medicine editors defended the work and said the request to remove it is not how scientific discourse should come about. Guyatt called the attempt to stop publishing "foolish".
In the newspapers, researchers sought to assess the potential impact of eating three fewer servings of red meat or processed meat each week. Considering that the average person in North America and Western Europe eats two to four servings a week, they said the evidence of reduction was not convincing.
For example, they found that cutting three portions of red meat a week would result in seven fewer cancer deaths per 1,000 people.
Based on the analysis, the researchers said people need not reduce for health reasons. But they noted that their own advice was weak and acknowledged that they did not take into account factors such as animal welfare and tolling meat production in the environment.
In fact, the case where meat production is bad for animal welfare and the environment is stronger than the case when it is bad for human health, according to a editorial accompanying the report.
"Both problems are likely to influence people and they have the added benefit of empirical evidence behind them," wrote Dr. Aaron Carroll and Tiffany Doherty of the Indiana University School of Pediatrics and Adolescent Comparative Research Center. Medicine. "And if they result in reduced meat consumption and some receive a small health benefit as a side effect, everyone wins."
Not all report authors agreed with their conclusions. Three of the 14 researchers said they supported reducing red and processed meats. A co-author of one of the reviews is also among those who asked for a delay in publishing.
Those who pushed to postpone the publication also wondered why certain studies were included in the reviews while others were left out.
Dr. Frank Hu, which heads the Harvard School of Health's Department of Nutrition, also noted that about one-third of American adults eat at least one serving of red meat a day. He said the benefits of the reduction would be greater for those who eat such large amounts.
Still, other researchers not involved in the reviews have criticized nutrition science for producing weak and conflicting findings. Dr. John IoannidisStanford University professor of medicine, said such advice can divert clearer and more effective messages, such as limiting how much we eat.
As for his own diet, Guyatt said he no longer believes that red or processed meats pose significant health risks. But he said he still avoids them out of habit and animal welfare and for environmental reasons.