Are healthier diets more sustainable? A cross-sectional assessment of 8 diet quality indexes and 7 sustainability metrics

Greater diet quality index scores were associated with lower daily per capita greenhouse gas emissions, cumulative energy demand, land use, and fertilizer nutrients.

• Higher scores on most diet quality indexes correlated with reduced greenhouse gas emissions, with a decrease of 0.908 to 0.250 carbon dioxide equivalents per unit increase in diet quality z-score.
• Cumulative energy demand decreased by 2.699 to 0.202 megajoules for higher diet quality index scores.
• Increases in diet quality were linked to lower land use, with reductions ranging from 0.002 to less than 0.001 hectares.
• Higher diet quality scores were associated with increased water scarcity footprint, with an increase of 343 to 649 liters per unit increment.
• Diet costs also increased with higher diet quality scores, ranging from 0.037 to 1.125 US dollars.
• Diet quality indexes emphasizing plant-based foods were linked to more favorable sustainability outcomes compared to those focusing on nutrients or animal-based foods.

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