For the study, Masters and his co-investigators sought to identify which foods would be the most sustainable way to meet nutritional requirements, based on the Healthy Diet Basket targets used for global monitoring by U.N. agencies and national governments around the world.
The team analyzed three kinds of data about each food item: its availability and price in each country, how much of each country’s food supply it accounted for, and the global average greenhouse gas emissions associated with that product.
For each country, they modeled five diets: the healthiest diet with the lowest emissions, the healthiest diet at the lowest cost, and three versions of diets based on the most commonly consumed foods.
“In general, choosing less expensive options in each food group is a reliable way to lower the climate footprint of one’s diet,” said Elena M. Martinez, one of the study’s lead authors, who completed the work as a doctoral student and postdoc at the Friedman School. “This new study extends that to the extremes, asking which items could meet health needs with the smallest possible climate footprint,” she added.
In the reference year of 2021, a healthy diet using the most commonly consumed products in each food group emitted 2.44 kilograms of CO₂-equivalent emissions per person per day and cost a global average of $9.96 per day.
In contrast, the benchmark diet to minimize climate harms would have emitted only 0.67 kilograms and cost $6.95. A healthy diet designed to minimize monetary cost would have emitted 1.65 kilograms and cost $3.68.
A third scenario that blended the most commonly consumed products with lower-cost healthy choices fell in between, costing about $6.33 per day and producing 1.86 kilograms of emissions—still well below typical diets, though not as low as the cheapest or lowest-emission options.
