A new study indicates there are few health benefits to cutting down on red meat - but experts say the findings are flawed and harmful.
The series of reviews into the relationship between meat consumption and health, which included data from New Zealand and Australia, have been published in medical journal Annals of Internal Medicine.
Canadian, Spanish and Polish researchers found little to no link between eating less red or processed meat and a reduced risk of health problems, and a panel of 14 experts have recommended most adults make no changes to their current meat consumption. This advice directly contradicts the majority of existing research on the subject, which has found a connection between a high-meat diet and an increased risk of cancer as well as heart disease and diabetes.
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- Meat group says New Zealand already adopting diet recommendations
In the wake of the study's release, multiple health experts, including Kiwis, have levelled intense criticism at how the research was conducted.
Some 54,000 participants took part in 12 randomised trials involving comparison groups which followed diets with different levels of meat consumption. Cohort studies, in which millions of people answered questionnaires about their meat-eating habits, were also used.
The University of Auckland's Epidemiology Professor Rod Jackson said medium to long-term studies can't provide useful information because inherent biases are "almost impossible to deal with".
"The misinformation given to the public, based on the result of these two types of seriously flawed study designs... have led to huge confusion and likely harm," he says.
"This is not a criticism of the researchers' ability to design studies, although they should have realised by now that the studies can’t be done well."
He says past trials have proven it's incredibly difficult to get participants to strictly adhere to controlled diets for more than a month or two, most people can't remember what they've eaten with accuracy and participants will often exaggerate their adherence to please researchers.
Jackson says researchers need to rethink what they consider acceptable evidence and move towards studies that bring together a wide range of evidence measuring different outcomes.
"This is messy and requires people with serious expertise and experience, but evidence is messy. It doesn’t matter how many meta-analyses of randomised trials and cohort studies are done and how many millions of people are included. They are still seriously flawed."
Jim Mann of the University of Otago says the study's "weak recommendations" are based on poor evidence and are unhelpful and potentially misleading.
He says the "self-selected" panel (which does not represent any organisation or government) should have taken into account the environmental benefits on reduced meat consumption before recommending people make no changes to their diet.
"In my opinion it is irresponsible not to consider sustainability and planetary health (a key, if not the major, determinant of the health of future generations) when developing nutrient and food-based dietary guidelines."
Professor Mark Wahlqvist, director of the Asia Pacific Health and Nutrition Centre, called the study "provocative and largely unhelpful".
Other experts have pointed out that there was only a small difference in meat intake between participants who followed the reduced diet and those who didn't, and that the panel's recommendations don't necessarily align with the study's findings.
Another subject of controversy is that several of the Australian studies were funded by Meat and Livestock Australia. Authors of another of the papers received personal funding from powerful food companies such as Dairy Farmers of Canada, PepsiCo, Nestle and Kellogg.
The authors of an editorial accompanying the study say while the findings will be "controversial", they're based on the most comprehensive reviews of the evidence and critics will be hard-pressed to build an argument against them.