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The environmental and health benefits of forgoing red meat are strong. For dairy? Not so much.  

DAILY SCIENCE

The environmental and health benefits of forgoing red meat are strong. For dairy? Not so much.  

Most research treats dairy and meat substitutions as a single unit. When a new study disentangled them, they arrived at some striking results.
March 8, 2024

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Substituting meat and dairy with more plant-based foods in our diets can achieve benefits for human and environmental health: this is a well-known fact. What’s perhaps less known is that these benefits can vary widely, depending on precisely which animal-based foods are displaced, a new study finds.

In fact to date, very little research has actually looked at dairy and meat substitutions separately, treating them as a unit instead—even though these food groups have very different nutritional profiles and environmental impacts. 

Disentangling the two was the goal of the new Nature Food study, from a team of UK-Canadian researchers. Their inspiration came from the recently updated Canadian national food guide, which suggests that Canadians should up their daily intake of plant proteins. 

To explore the possible consequences of these dietary shifts, the researchers combined data from a national nutrition survey, with estimated greenhouse gas emissions and the relative health risks associated with different types of foods. Then they explored how those health and environmental impacts would change, if different shares—either 25 or 50%—of dairy or red meat were subbed out and replaced with plant proteins like nuts, legumes, soy-based meat alternatives, and plant milks instead.

As the share of plants grew in the respective diets, it led to eating patterns that, overall, had a lower carbon footprint, paired with several nutritional benefits too. Reducing meat and dairy products led to declines in excess salt and saturated fat consumption, and also decreased the share of people who would suffer from potassium and iron deficiencies. Increasing the share of plants in a diet overall lowered the risk of chronic disease too, which played out in longer individual life expectancies of up to 9 months. That was especially notable for Canadian men, who tend to eat more red meat than women do. 

 

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However, as they drilled down into the nutritional profiles, the researchers also revealed some stark differences between the impacts of meat and dairy substitutes. In turn, these highlighted some important trade-offs between health and environmental goals. 

On the one hand, replacing half of the red meat in the average Canadian diet with plant proteins would shrink an individual’s carbon footprint by a striking 25%. But replacing 50% of dairy produced with plant alternatives only erased 5% of dietary emissions. 

The relatively small size of these environmental gains for dairy substitutes were put into perspective when they were weighed up against some of the nutritional losses driven by a shift to plants, which the researchers delved into as well. In both meat- and dairy substitute diets there were some small, relatively insignificant declines in protein and vitamin D levels. But the most striking figure was that a 50% dairy replacement would lead to a 14% increase in the number of people experiencing a calcium deficit in Canada—an ingredient that is critical for the growth of healthy muscles and bones.

“It was interesting to see how the type of animal protein being replaced—being either red and processed meat or dairy—led to different outcomes,” says Olivia Auclair, the paper’s first author and recent PhD graduate in McGill University’s Department of Animal Science. “Substituting dairy led to smaller gains to life expectancy, smaller reductions to diet-related greenhouse gas emissions, and increased the proportion of the population below calcium requirements by up to 14%.”

By drilling into the unique differences between meat and dairy substitutes, the researchers were therefore able to identify the dietary changes that can make both a real nutritional and environmental difference. In this case, curbing red meat consumption appears to be the most effective target for bringing down dietary emissions, without those trade-offs in nutrition: eating less meat and more plants would have clear environmental and health co-benefits. 

Previous studies have found that Canadian citizens are more engaged in reducing their red meat intake than their dairy. So, using information from the recent study, national guidelines could also build on this willingness, to encourage more climate-friendly diets. 

“Improving our health and reducing our carbon footprint does not necessarily require drastic changes, such as completely shifting our dietary patterns or excluding certain foods altogether, but making simple, conscious changes to our diets that should be well within reach for most Canadians,” says Auclair.

The implications of the study go beyond Canada too. Carefully tailored national dietary guidelines could deliver more bang for their buck where climate and health are concerned—focusing on what really works, while limiting the trade-offs. 

Auclair et. al. “Partial substitutions of animal with plant protein foods in Canadian diets have synergies and trade-offs among nutrition, health and climate outcomes.” Nature Food. 2024. 

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