Improving diet sustainability through evolution of food choices: review of epidemiological studies on the environmental impact of diets

Abstract

The Food and Agriculture Organization defines sustainable diets as nutritionally adequate, safe, healthy, culturally acceptable, economically affordable diets that have little environmental impact. This review summarizes the studies assessing, at the individual level, both the environmental impact and the nutritional quality or healthiness of self-selected diets. Reductions in meat consumption and energy intake were identified as primary factors for reducing diet-related greenhouse gas emissions. The choice of foods to replace meat, however, was crucial, with some isocaloric substitutions possibly increasing total diet greenhouse gas emissions. Moreover, nutritional adequacy was rarely or only partially assessed, thereby compromising the assessment of diet sustainability. Furthermore, high nutritional quality was not necessarily associated with affordability or lower environmental impact. Hence, when identifying sustainable diets, each dimension needs to be assessed by relevant indicators. Finally, some nonvegetarian self-selected diets consumed by a substantial fraction of the population showed good compatibility with the nutritional, environmental, affordability, and acceptability dimensions. Altogether, the reviewed studies revealed the scarcity of standardized nationally representative data for food prices and environmental indicators and suggest that diet sustainability might be increased without drastic dietary changes.

Keywords: diet cost; food choice; greenhouse gas emissions; nutritional quality; public health; sustainable diet.

Figure 1

Relationship between total quantities ingested and diet-related GHGEs (panel A) and between total energy intake and diet-related GHGEs (panel B) for adults participating in the INCA 2 study (n = 1918). Adapted with permission from Vieux et al. after recalculation of diet-related GHGEs for 391 GHGE food values (instead of 73). Abbreviations: CO₂e, carbon dioxide equivalents; GHGEs, greenhouse gas emissions; INCA 2, Second Individual and National Survey on Food Consumption.

Figure 2

Energy contribution of main food groups to the diets classified as average (whole sample, n = 1142 women) and more sustainable (n = 229) for women participating in the INCA 2 survey. The average diets represent mean intakes in women; more sustainable diets were those with both diet-related GHGEs under the median and a PANDiet score above the median; Adapted with permission from Vieux et al. Values are means. Asterisks indicate a significant (P < 0.01) difference between the average diet and the more sustainable diets, assessed with analysis of means. Abbreviations: GHGEs, greenhouse gas emissions; INCA 2, Second Individual and National Survey on Food Consumption.

Figure 3

Mean dietary GHGEs per 2000 kcal for high meat-eaters (≥100 g/d; n=8286), medium meat-eaters (50–99 g/d; n=11971), low meat-eaters (>0 and<50 g/d; n=9332), fish-eaters (n=8123), vegetarians (n=15 751), and vegans (n=2041) in the United Kingdom. Adapted with permission from Scarborough et al. Abbreviations: CO₂e, carbon dioxide equivalents; GHGEs, greenhouse gas emissions.

Figure 4

Mean dietary GHGEs (panel A) and mean dietary cost (panel B) by quintile of accordance with the DASH diet as a whole and with food groups of the DASH diet. Adapted with permission from Monsivais et al. Abbreviations: CO₂e, carbon dioxide equivalents; DASH, Dietary Approaches to Stop Hypertension; GHGEs, greenhouse gas emission; Q1, lowest accordance with DASH diet; Q5, highest accordance with DASH diet; RPM, red and processed meat.