In a study modeling the life cycle of 321 foods, the vegetarian diet had much lower impacts on the environment than did those containing animal proteins
Dr. Miriam Nelson, President of Hampshire College, and a team of scientists from Tufts University and University of New Hampshire have published research revealing the environmental impact of the recommended diets in the Dietary Guidelines for Americans. The senior author of the paper, Nelson is a prominent health and nutrition scholar, former adviser to the Dietary Guidelines for Americans, and a leader of the sustainability movement. She and her colleagues’ new research advances sustainability through findings that promise to inform and shape food policy nationally and globally.
According to the UN Food and Agricultural Organization, sustainable diets are those with low environmental impacts, which ensure the security of food sources and will advance healthy human life for generations. Sustainable diets also maintain and protect environmental ecosystems and optimize natural resources, are socially just, and provide sound nutrition.
The new research, published in the August issue of The Lancet Planetary Health, analyzed environmental impacts of the healthy diet patterns recommended in the Dietary Guidelines for Americans: specifically, their impact on climate change, land use, water use, water quality (fresh and marine), and air quality. The study by Dr. Nicole Tichenor Blackstone, affiliated with University of New Hampshire and Tufts University, Dr. Nelson, and three partners, titled “Linking sustainability to the healthy eating patterns of the Dietary Guidelines for Americans,” looks at the environmental impacts of three diets: The Healthy US-Style diet, incorporating lean meats as a protein source; Healthy Mediterranean-Style diet, with seafood as a main protein source; and Healthy Vegetarian diet, with plant-based proteins and eggs.
The study found that the vegetarian diet had much lower impacts on the environment (from 42 to 84 percent lower) than did those containing animal proteins. The scientists believe this is the first study to link environmental impacts to the actual food patterns in the Dietary Guidelines for Americans.
“It’s important to think about the sustainability of our food because our health is affected not only by the food we eat but also, by the health of the environment where we live and work,” Nelson says. “It’s vital that we understand sustainability of our choices in the broad sense, spanning environmentalism and just as importantly social justice, inclusive prosperity, and equity for our neighbors and fellow residents. Given the influence of the Dietary Guidelines on food systems, incorporating sustainability into the government’s recommendations has the potential to have great benefit in terms of human health beyond nutrition, economic equity, and long-term food security.”
The team conducted the study to help inform future policy in the United States and abroad. The differences among the three dietary patterns center primarily on the amounts and types of protein recommended, as well as the amounts of fruit, dairy, whole grains, and discretionary calories. The Mediterranean pattern recommends almost double the amount of seafood compared to that of the U.S. diet. The Vegetarian pattern, on the other hand, relies on plant-based proteins and eggs and recommends lower overall consumption of protein.
The team’s research involved determining the environmental impacts of 321 foods that collectively comprise the three recommended diets. For each food, the team modeled its life cycle from its source on a farm, ranch, or body of water and estimated such impacts as the use of natural resources, the generation of pollution, and impairment of air and water quality that occur through a product’s supply chain to packaging.
Issued jointly every five years since 1980 by the U.S. Department of Agriculture and the Department of Health and Human Services, the Dietary Guidelines for Americans are the foundation of nutrition policy, driving more than $80 billion in federal spending. The two agencies work together to ensure that the latest science about the role of nutrition in human health is incorporated into the national guidelines.
In advising the development of the 2015–2020 guidelines, Dr. Nelson led the Subcommittee on Sustainability and Food Safety, which in 2015 authored the first-ever chapter on sustainability. Serving on the subcommittee with Nelson was Timothy Griffin, of the Friedman School of Nutrition Science and Policy, who has continued working with Nelson and serves as coauthor of the new research in The Lancet Planetary Health. They and their subcommittee colleagues referenced a growing number of recent studies demonstrating how a diet higher in plant-based foods and lower in animal-based foods is not only healthier, but also has less environmental impact on energy, land, and water use.
Despite unprecedented public support, this and other sustainability language was not included in the final published 2015–20 Dietary Guidelines for Americans, because the Department of Health and Human Services and the Department of Agriculture determined the issue to be beyond the report’s scope. The topic has been debated publicly, with a wide range of interests contributing viewpoints.
The subcommittee’s work influenced the Canadian government to embed sustainability in its national guidelines. An increasing number of nations are incorporating sustainability into dietary recommendations; other countries such as the Netherlands, Sweden, and Brazil have developed guidelines that promote planetary health.
The findings of the new study add to the body of literature suggesting that diet patterns that are higher in plant-based foods and lower in animal-based foods are better for the environment. “Given the evidence and the scale of influence of the Dietary Guidelines for Americans on food systems,” the scientists conclude, “incorporating sustainability into them should be prioritized.”
The article’s five authors and their affiliations are:
The Lancet Planetary Health has also published a Commentary about the study, advocating for the inclusion of sustainability in nutrition guidance: “Because the aim of national dietary guidelines is to provide advice for constructing healthy diets, the guidelines should arguably consider both direct and indirect health consequences of the nutritional recommendations.”
The Commentary continues, “Recommendations for healthy diets are not complete if they ignore the indirect health impacts caused by environmental changes associated with food production and consumption.”
The Lancet Planetary Health is an open-access journal publishing high-quality original research that explores human health within such contexts as climate change, water scarcity, food and nutrition, sustainable fishing, agriculture, pollution, waste management, air quality, and disease.