New research from Johns Hopkins Center for a Livable Future shows that no single diet can cut greenhouse gas (GHG) emissions and that policymakers should support diets that fall in line with national nutrition requirements, culture, and trade.
“Our research indicates there’s no one-size-fits-all diet to address the climate and nutrition crises,” says Dr. Keeve Nachman, senior author of the study, in a press release. “Context is everything, and the food production policies for each country must reflect that.”
The study, “Country-specific dietary shifts to mitigate climate and water crises,” looks at how shifting to diets with a lower carbon footprint in 140 countries affects emissions and freshwater use. The results could guide policymakers in providing enough, nutritious, climate-friendly food that fits national tastes, the authors say.
If all countries would adopt the typical diet of high-income countries—hypercaloric, and rich in meat and dairy—then GHG emissions and water footprints related to diets would soar by 135 percent and 47 percent respectively, the researchers warn. Recent reports have shown fast industrialization in countries such as China is driving a strong shift towards the Western diet.
Switching to veganism which has the lowest footprint per capita across all 140 countries studied, could cut GHG emissions by as much as 70 percent per person, says the report. In the United States, for example, vegans would cause only 16 percent of the emissions of animal-based diets, even if they ate more to get all their nutrients. But it is highly unlikely that countries can shift entirely to a single diet, the authors say.
“There will always be trade-offs. Environmental impact alone cannot be a guide for what people eat; countries need to consider the totality of the nutritional needs, access, and cultural preferences of their residents,” says Dr. Martin Bloem, study co-author and director of the Johns Hopkins Center for a Livable Future.
Researchers confirmed again that cow, sheep, and goat meat cause the highest emissions in meat production by a margin, with beef 316 times more carbon-intensive than pulses. But not all stakes are made the same, which can change a diet’s footprint; beef’s contributions to emissions can vary —for example, one pound of beef from Paraguay produces 17 times more GHGs than the same amount of Danish beef, as Paraguayans continue to clear their forests to make space for livestock.
But overall, eating meat once per day may be better than switching to vegetarian diets with dairy and eggs, the research shows. The dairy industry, along with meat, is on its way to becoming a bigger GHG emitter than the biggest oil companies, a recent report says. In 91 percent of the countries surveyed, choosing to eat mostly plants with a little meat was less than half as carbon-intensive than relying on vegetarian diets that included dairy and eggs.
The study shows that diets providing animal protein from small fish, mollusks, and insects had an environmental impact almost as low as a vegan diet across countries. In almost half the countries, eating so-called low-food chain diets also fulfills vitamin B12 requirements for adults, cutting out the need for supplements.
“The good news is this research can be a part of the solution, as it now gives policymakers a tool to develop nationally appropriate strategies, including dietary guidelines, that help meet multiple goals,” says Dr. Bloem.