Most things you’ve heard about eating meat are wrong, say Irish scientists

A series of studies on the health impact of eating red and processed meats had a seismic impact on dietary advice across the world over the past seven years. Other studies published since have exposed their flaws, yet they continue to be at the forefront of global nutrition policy.

Reports from EAT-Lancet Commission on Food, Planet, Health, published in 2019, and from the Global Burden of Diseases (GBD) Risk Factors Collaborators in papers dating from 2017 were most influential in prompting the shift.

The message was clear: A 2020 GBD study found nearly 900,000 deaths worldwide in 2019 were caused by consumption of red meat, making it the fifth-largest dietary risk factor. Recommendations called for dramatic reductions or total exclusion of animal-source foods, particularly red meat and dairy from the human diet.

They suggested these dietary shifts would not only benefit human health but also planetary health – it was hailed as shaping “the diet of the future” – as red meat was an inherently harmful food. The only problem is that much of this research has been shown to be flawed, lacking transparency in how conclusions were reached, and yet it continues to be central to dietary advice of policymakers and health organisations.

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Two of Ireland’s leading food and diet specialists, Prof Alice Stanton of the Royal College of Surgeons in Ireland and Prof Patrick Wall of University College Dublin have led international efforts to have the studies corrected. Their motivation, they say, is the health consequences of flawed data amid continuing “misinformation” about meat diets.

When they see adverse nutritional claims associated with meat, they regard this as more ammunition for their cause. But many of these nutritional claims are based on flawed science

—  Prof Patrick Wall

In her latest paper published in npj Science of Food this month, Stanton details “unacceptable use of substandard metrics in policy decisions which mandate large reductions in animal-source foods”.

In short, major studies recommending plant-based diets are based on bad data and incorrect assumptions, she says. The 2020 GBD study underestimated the importance of it being easier for bodies to take in proteins and micronutrients from meat than plant-based food. The EAT-Lancet report “would not meet nutritional requirements for adults”, she adds.

Stanton points to influential groups which contend that animal-source foods and particularly red meat cause heart attacks, stroke and cancers, especially those groups advocating for “an almost completely plant-based diet”, when some plant-based diets would cause nutritional deficiencies including anaemia – especially among under-fives, women of childbearing age and older people.

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She highlights strong evidence that unprocessed red meat delivers the most vitamin B12 intake in human diets, while delivering key compounds for metabolism. Going vegan means some women need iron supplements, she says, while many older people need the high-quality protein and key minerals that meat provides in protecting against osteoporosis, dementia and fragility.

Stanton, an expert in cardiovascular therapeutics, acknowledges possible risks from excess consumption of meat, ie more than five times a week, “but there are considerably greater risks from dramatic reductions or exclusion of meat, dairy, fish and eggs”. Equally, those risks could be due to an unbalanced diet or high consumption of calories. With evidence around excessive consumption of red meat being “extremely uncertain”, it shouldn’t be used to guide policy decisions, she says.

Wall, a former head of the Food Safety Authority of Ireland (FSAI) and chairman of the European Food Safety Authority, is concerned by the extent to which flawed science is circulated and incorporated into nutrition advice. He accepts many people are against meat for animal welfare reasons or because of the environmental impact of livestock production, “which are valid concerns”.

But he draws the line with dietary advice: “When they see adverse nutritional claims associated with meat, they regard this as more ammunition for their cause. But many of these nutritional claims are based on flawed science.”

Equally, he questions the validity of some contentions when it comes to nature in crisis. “There is a lot of talk about a plant-based diet as healthier for us and for the planet. However, given the biodiversity crisis we are currently experiencing, partly as a result of all the agrochemicals we are currently using, there is no talk of the need for safer plant protection products or GMO [genetically modified organism] disease-resistant crops that will not require sprays,” he notes.

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Stanton accepts “there are extremes at either end of the debate”, but is grateful their position is increasingly acknowledged by “really influential scientific groups”, though the reports – principally in the Lancet – remain uncorrected. She and five other leading researchers, including Wall, detailed flaws in a 2021 letter which was published nine months later.

They forced an acknowledgment, she says, on the lack of evidence that consuming unprocessed red meat was causing hundreds of thousands of deaths.

They asked for the evidence that red meat consumption was causing deaths in such high numbers. They were told a future report would acknowledge errors. This was published another nine months later. While the basis for those conclusions was not outlined, there was a comprehensive article with new figures saying a person could eat up to 200g a day – ie, a small steak – with no evidence it would cause harm.

Yet the 2019 figures remain uncorrected, Stanton says, and other researchers are still using that data. It is influencing international guidelines on diet from the World Wildlife Fund and nutritional advice in Nordic countries. “It’s continuing to influence policymakers – and it’s worrying.”

The World Health Organisation has highlighted weaknesses in the research. HSE advice through the FSAI recommends a maximum of 75g of red and processed meat daily. This allows for consumption three to four times a week, which Stanton regards as “reasonable” as part of a balanced diet.

The NHS in the UK advises beef, lamb and pork are good sources of protein and can form part of a balanced diet, but eating more than 90g daily can raise the risk of bowel cancer.

The GBD study did not take into account the contribution of moderate meat consumption towards nutrient adequacy, Stanton says.

In response, the Lancet group said: “The GBD 2019 Article, EAT-Lancet Commission on Food, Planet, Health, and Lancet Countdown on health and climate change reports, were each published following independent, external peer-review.”

“Scientific discussion and debate are an important part of the scientific process, and the Lancet journals welcome responses from readers and the wider scientific community to content published in the journals,” it added.

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A vegetarian does not eat animal flesh such as meat, poultry or fish. A vegan diet is a stricter one, avoiding dairy, eggs and ingredients derived from animals. According to US National Institutes of Health, in most cases vegetarian diets are beneficial in prevention and treatment of diseases, such as cardiovascular disease (CVD), hypertension, diabetes, cancer, osteoporosis, renal disease and dementia, as well as diverticular disease, gallstones and rheumatoid arthritis.

The American Health Association advises “diets rich in animal-based and minimally processed plant foods are associated with poor and optimal cardiovascular health, respectively”. This explains why CVD rates are much higher in Western countries, where intake of animal-based foods is 140 per cent more than dietary recommendations, while intake of raw plant foods is relatively low. However, there is a scarcity of studies specifically exploring benefits of plant-based diets.

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Stanton acknowledges food production and consumption contribute to the world’s climate and biodiversity crises, being responsible for about a third of greenhouse gas emissions. Conversion of natural ecosystems to agricultural land has been deemed “the largest threat to species extinction”.

So there is a need “to transform our food system so that all have access to healthy diets, while at the same time safeguarding the planet’s health”. How that is achieved induces intense debate – to what extent does food production, processing, distribution, retailing and consumption have to change? Many researchers say dietary shift is critical, “but rather than recommending moderation of consumption patterns, they require considerable reductions, or even total exclusion of animal-source foods”.

Stanton concludes: “It’s really important that health professionals, doctors, nutritionists and policymakers are aware of this discussion.”

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