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

Zach Conrad; Andrew L Thorne-Lyman; Songze Wu; Chloe DiStaso; Madison Korol; David C Love

doi:10.1016/j.ajcnut.2024.11.027

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

Am J Clin Nutr. 2024 Dec 9:S0002-9165(24)01422-9. doi: 10.1016/j.ajcnut.2024.11.027. Online ahead of print.

Authors

Zach Conrad¹, Andrew L Thorne-Lyman², Songze Wu³, Chloe DiStaso⁴, Madison Korol⁵, David C Love⁶

Affiliations

¹ Department of Kinesiology, William & Mary, Williamsburg, VA 23185, USA; Global Research Institute, William & Mary, Williamsburg, VA 23185, USA. Electronic address: zsconrad@wm.edu.
² Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21202, USA; Center for a Livable Future, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA; Center for Human Nutrition, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA. Electronic address: athorne1@jhu.edu.
³ College of Arts & Sciences, William & Mary, Williamsburg, VA 23185, USA. Electronic address: swu11@wm.edu.
⁴ College of Arts & Sciences, William & Mary, Williamsburg, VA 23185, USA. Electronic address: ctdistaso@wm.edu.
⁵ College of Arts & Sciences, William & Mary, Williamsburg, VA 23185, USA. Electronic address: mlkorol@wm.edu.
⁶ Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21202, USA; Center for a Livable Future, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. Electronic address: dlove8@jhu.edu.

PMID: 39662595
DOI: 10.1016/j.ajcnut.2024.11.027

Abstract

Background: A comparison of commonly used diet quality indexes (DQIs) and their association with multiple indicators of sustainability has not been performed, which limits policy action.

Objective: To evaluate the associations between eight DQIs and seven sustainability indicators in a nationally representative sample in the United States.

Design: In this cross-sectional analysis, dietary data from the National Health and Nutrition Examination Survey (2011-2018, n=18,522 ≥20 y) were merged with data on greenhouse gas emissions, cumulative energy demand, water scarcity footprint, land, fertilizer nutrients, pesticides, and food prices from multiple publicly available databases. Diet quality was measured using the Healthy Eating Index-2020 (HEI-2020), Alternate Healthy Eating Index-2010 (aHEI), Mediterranean Diet Score (Med), Alternate Mediterranean Diet Score (aMed), Healthful Plant-based Diet Index (hPDI), Planetary Health Diet Index for the United States (PHDI), Dietary Approaches to Stop Hypertension (DASH), and Nutrient-Rich Foods Index 9.3 (NRF9.3). The relationship between each diet quality index and sustainability indicator was assessed using linear regression.

Results: Greater scores on most or all DQIs were associated with lower daily per capita greenhouse gas emissions (β= -0.908 to -0.250 carbon dioxide equivalents per 1 unit increment in diet quality z-score), cumulative energy demand (β= -2.699 to 0.202 MJ), land (β= -0.002 to <-0.001 ha), and fertilizer nutrients (β= -0.026 to 0.007 kg). By contrast, greater scores on most or all DQIs were associated with greater water scarcity footprint (β= 343 to 649 L equivalents) and diet cost (β= 0.037 to 1.125 US$), and had mixed associations with pesticide use (β= -0.001 to <-0.001 kg). Greater scores on aHEI-2010 and hPDI were associated with the greatest ratio of favorable-to-unfavorable sustainability outcomes (5:2 each), followed by PHDI (4:1), Med and aMed (4:2 each), HEI-2020 and DASH (3:2 each), and NRF9.3 (3:4).

Conclusions: All DQIs had sustainability trade-offs, but those that emphasized plant-based foods, rather than nutrients or animal-based foods, were associated with more favorable sustainability outcomes.

Keywords: Cost; Diet quality; Greenhouse gas; Index; NHANES; Sustainability.