A Cross-Sectional Study of the Dietary Carbon Footprints of US Schoolchildren

Objectives: This study's main objective was to examine the association between dietary greenhouse gas emissions (GHGEs) and diet quality among U.S. primary and secondary schoolchildren. Our secondary objectives were to identify demographic characteristics associated with higher-GHGE diets and to assess the relationship between school meal consumption and dietary GHGE. Methods: We conducted a cross-sectional secondary analysis of dietary intake data from 2165 primary and secondary students participating in the nationally representative 2014-2015 US School Nutrition and Meal Cost Study (SNMCS). Dietary GHGEs (kg CO₂-equivalents per 1000 kcal) were estimated by linking reported foods to an environmental impact database. Diet quality was assessed using the Healthy Eating Index-2010 (HEI). Students were categorized into GHGE groups, and differences in total HEI and component scores were examined using appropriate statistical tests. Statistical significance was set at p < 0.05. Results: The average dietary GHGE of the sample was 3.64 kg CO₂-equivalent per person per day. Overall, HEI scores did not differ between the GHGE groups (p = 0.22). However, compared to the high-GHGE group, the low-GHGE group scored significantly higher on some HEI-2010 components, such as fatty acid ratios (p < 0.0001) and sodium (p < 0.0001), and significantly lower on others, such as dairy (p < 0.0001), total protein foods (p < 0.0001), and refined grains (p < 0.0001). Male students and students who ate school meals on the day of recall had higher odds of being in the high-GHGE group compared with their respective reference groups. Conclusions: Lower dietary carbon footprints are achievable without sacrificing overall diet quality, but tradeoffs in specific dietary components indicate the need for additional research and care in recommending diet changes or setting school policies.