Researchers from the University of Michigan evaluated more than 5,800 foods, ranking them by their nutritional disease burden to humans and their impact on the environment. A major finding: Substituting 10% of daily caloric intake from beef and processed meats for a mix of fruits, vegetables, nuts, legumes, and select seafood could reduce a dietary carbon footprint by one-third and allow a person to gain 48 minutes of healthy life per day.
"Generally, dietary recommendations lack specific and actionable direction to motivate people to change their behavior, and rarely do dietary recommendations address environmental impacts," said Katerina Stylianou, who did the research as a doctoral candidate and postdoctoral fellow in the the Department of Environmental Health Sciences at U-M's School of Public Health. She currently works as the Director of Public Health Information and Data Strategy at the Detroit Health Department.
The work is based on the Health Nutritional Index, which the investigators developed in collaboration with nutritionist Victor Fulgoni III from Nutrition Impact LLC. The Index calculates the net beneficial or detrimental health burden in minutes of healthy life associated with a serving of food consumed. It is an adaptation of the Global Burden of Disease (GBD), in which disease mortality and morbidity are associated with a single food choice. For the Index, researchers used 15 dietary risk factors and disease burden estimates from the GBD and combined them with the nutrition profiles of foods consumed in the United States. Foods with positive scores add healthy minutes of life, while foods with negative scores are associated with health outcomes that can be detrimental for human health.
To evaluate the environmental impact of foods, the researchers used IMPACT World+, a method to assess the life cycle impact of foods, and added improved assessments for water use and human health damages from fine particulate matter formation.
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The researchers classified foods into green, yellow, and red, based on their combined nutritional and environmental performances. The green zone represents foods that are both nutritionally beneficial and low-impact for the environment—this includes nuts, fruits, vegetables, legumes, whole grains, and some seafood. The red zone indicates foods that have either considerable nutritional or environmental impacts, and should be reduced or avoided; it includes mostly processed meats, as well as beef, pork, and lamb.The researchers note that nutritionally beneficial foods might not always generate the lowest environmental impacts, and vice versa.
"Previous studies have often reduced their findings to a plant vs. animal-based foods discussion," Stylianou said. "Although we find that plant-based foods generally perform better, there are considerable variations within both plant-based and animal-based foods."
The researchers suggest:
- Decreasing foods with the most negative health and environmental impacts including high processed meat, beef, shrimp, followed by pork, lamb and greenhouse-grown vegetables.
- Increasing the most nutritionally beneficial foods, including field-grown fruits and vegetables, legumes, nuts and low-environmental impact seafood.
