Diet Sustainability: A Global Investigation in Using Diet to Inform Food System Sustainability.

Abstract

Sustainable Development Goal #2 (SDG 2, Zero Hunger) was created to end hunger, achieve food security, improve nutrition, and promote sustainable agriculture by 2030; however, it is projected that 600 million people will remain hungry by 2030 based on current dietary and food insecurity trends (UNSTATS, 2022; UNSTATS, 2023). The Food and Agricultural Organization (FAO) of the United Nations defines a sustainable diet as a diet that is nutritionally adequate, affordable & accessible, and agriculturally sustainable, which is thereby both healthy for humans and protective of the environment (FAO, 2010). However, there is a lack of evidence to show that a healthy diet is broadly associated with a healthy environment, and significant gaps in data are stated by the FAO as a challenge to accurately reflect progress towards achieving the SDGs (FAO, 2023b; Tilman & Clark, 2014). Therefore, this study combined country-wide datasets published by the FAO and Global Dietary Database with the objectives to: 1) determine how metrics of nutritional adequacy, affordability and accessibility, and agricultural sustainability can be indicative of diet sustainability; 2) utilize pre-existing databases to identify gaps in progress towards SDG2 which contribute to high levels of undernourishment; 3) evaluate unique relationships between nutritional adequacy, affordability and accessibility, and agricultural sustainability across different regions globally; and 4) demonstrate the use of simplified and easily adoptable metrics which use currently available data for accurately informing regional food-system related policy. In line with these objectives, I defined three metrics of a sustainable diet for 143 countries using recent peer-reviewed methods for nutritional adequacy, the cost of healthy foods, and regenerative agriculture. The relationships between the three metrics were evaluated by Pearson’s correlation coefficient and linear regression analysis to determine how each metric is related in the context of a sustainable diet. These metrics were further combined into one overall sustainable diet index to determine whether this combination can accurately reflect the state of diet sustainability with respect to the prevalence of undernourishment and the goals of SDG 2. The results of this study support previous findings that a healthier diet is not always indicative of a healthier environment, as the metrics of nutritional adequacy and regenerative agriculture did not have a significant linear relationship (Tilman and Clark, 2014). However, when broken down by income-classification, defined by the World Bank, countries in the highest and lowest income groups were found to have opposite significant linear relationships with respect to nutritional adequacy and the cost of healthy foods. This study further revealed significant room for improvement in the calculation of metrics for nutritional adequacy, as low-income countries, which on average had the highest score for nutritional adequacy, were also observed to have the highest prevalences of undernourishment. In conclusion, the overall sustainable diet index served as a useful tool as a broader indicator of diet sustainability; however, the balance and contributions of each metric to the overall index were found to be where the important implications lie for accurately informing sustainable food system policy.