Dietary recommendations

Eating a hot dog could cost you 36 minutes of healthy life, while choosing to eat a serving of nuts instead could help you gain 26 minutes of extra healthy life, according to a University of Michigan study.

The study, published in the journal Nature Food, evaluated more than 5,800 foods, ranking them by their nutritional disease burden to humans and their impact on the environment. It found that substituting 10 percent of daily caloric intake from beef and processed meats for a mix of fruits, vegetables, nuts, legumes, and select seafood could reduce your dietary carbon footprint by one-third and allow people to gain 48 minutes of healthy minutes 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,” says Katerina Stylianou, who did the research as a doctoral candidate and postdoctoral fellow in 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.

This work is based on a new epidemiology-based nutritional index, the Health Nutritional Index (HENI), which the investigators developed in collaboration with nutritionist Victor Fulgoni III from Nutrition Impact LLC. HENI calculates the net beneficial or detrimental health burden in minutes of healthy life associated with a serving of food consumed.

Calculating impact on human health

The index is an adaptation of the Global Burden of Disease (GBD) in which disease mortality and morbidity are associated with a single food choice of an individual. For HENI, 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, based on the What We Eat in America database of the National Health and Nutrition Examination Survey. 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.

Adding environmental impact to the mix

To evaluate the environmental impact of foods, the researchers utilized IMPACT World+, a method to assess the life cycle impact of foods (production, processing, manufacturing, preparation/cooking, consumption, waste), and added improved assessments for water use and human health damages from fine particulate matter formation. They developed scores for 18 environmental indicators taking into account detailed food recipes as well as anticipated food waste.

Finally, researchers classified foods into three color zones: green, yellow, and red, based on their combined nutritional and environmental performances, much like a traffic light.

The green zone represents foods that are recommended to increase in one’s diet and contains foods that are both nutritionally beneficial and have low environmental impacts. Foods in this zone are predominantly nuts, fruits, field-grown vegetables, legumes, whole grains, and some seafood.

The red zone includes foods that have either considerable nutritional or environmental impacts and should be reduced or avoided in one’s diet. Nutritional impacts were primarily driven by processed meats, and climate and most other environmental impacts were driven by beef and pork, lamb, and processed meats.

The researchers acknowledge that the range of all indicators varies substantially and also point out 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 says. “Although we find that plant-based foods generally perform better, there are considerable variations within both plant-based and animal-based foods.”

Based on their findings, the researchers suggest:

• Decreasing foods with the most negative health and environmental impacts, including high processed meat, beef, and 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.

“The urgency of dietary changes to improve human health and the environment is clear,” says Olivier Jolliet, senior author of the paper and professor of environmental health sciences at U-M’s School of Public Health. “Our findings demonstrate that small targeted substitutions offer a feasible and powerful strategy to achieve significant health and environmental benefits without requiring dramatic dietary shifts.”

The project was carried out within the frame of an unrestricted grant from the National Dairy Council and of the University of Michigan Dow Sustainability Fellowship. The researchers also are working with partners in Switzerland, Brazil, and Singapore to develop similar evaluation systems there. Eventually, they would like to expand the system to countries around the world.