By eating less meat and more fruit and vegetables, the world could prevent several million deaths per year by 2050, cut planet-warming emissions substantially, and save billions of dollars annually in healthcare costs and climate damage, researchers said.
A new study published in the Proceedings of the National Academy of Sciences is the first to estimate both the health and climate change impacts of a global move towards a more plant-based diet, they said.
"We do not expect everybody to become vegan," said lead author Marco Springmann of the Oxford Martin Program on the Future of Food.
But if they did, they'd live longer and help reduce the changes that are skewing the climate.
"What we eat greatly influences our personal health and the global environment," Springmann said.
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The Oxford University researchers modeled the effects of four different diets by mid-century: a 'business as usual' scenario; one that follows global guidelines including minimum amounts of fruits and vegetables and limits on red meat, sugar and total calories; a vegetarian diet; and a vegan diet.
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Adopting a diet in line with the global guidelines could avert 5.1 million deaths per year by 2050, while 8.1 million fewer people would die in a world of vegans who do not consume animal products, including eggs and milk.
When it comes to climate change, following dietary recommendations would cut food-related emissions by 29 percent, adopting vegetarian diets would cut them by 63 percent and vegan diets by 70 percent.
Dietary shifts could produce savings of $700 billion to $1 trillion per year on healthcare, unpaid care and lost working days, while the economic benefit of reduced greenhouse gas emissions could be as much as $570 billion, the study found.
The researchers found that three-quarters of all benefits would occur in developing countries, although the per capita impacts of dietary change would be greatest in developed nations, due to higher rates of meat consumption and obesity.
The economic value of health improvements could be comparable with, and possibly larger than, the value of the prevented damage from climate change, they added.
"The value of those benefits makes a strong case for increased public and private spending on programs aimed to achieve healthier and more environmentally sustainable diets," Springmann said.
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The study looked at regional differences which could be used to identify the most suitable interventions for food production and consumption, Springmann said.
For example, lower red meat consumption would have the biggest effect in East Asia, the West and Latin America, while boosting fruit and vegetable intake was found to be the largest factor in cutting deaths in South Asia and sub-Saharan Africa.
Lower calorie intake, leading to fewer overweight people, would play a key role in improving health in the Eastern Mediterranean, Latin America and Western nations, the study said.
But it will not be easy. To achieve a diet that sticks to common guidelines would require a 25 percent increase in the number of fruits and vegetables eaten globally, and a 56 percent cut in red meat.
Overall, humans would need to consume 15 percent fewer calories, it said.
"We do not expect everybody to become vegan," Springmann added. "But climate change impacts of the food system will be hard to tackle and likely require more than just technological changes. Adopting healthier and more environmentally sustainable diets can be a large step in the right direction."
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