From Boomers to Zoomers: Generational Differences in US Dietary Carbon Footprints

Objectives: Understanding the influence of generational cohorts on dietary carbon footprints may assist programming to reduce greenhouse gas emissions (GHGE) from the food system, but little is known about this. The primary objectives were to test whether US generational cohorts differ in their dietary GHGE or intake of beef, a very high-GHGE food. The secondary objectives examined whether GHGE or beef intake changed over time in these cohorts. Methods: Cross-sectional dietary recall data from two non-consecutive days for adults (≥ 18 yrs; N=8,471) in the 2015-2018 National Health and Nutrition Examination Survey (NHANES) were linked to the updated Database of Food Recall Impacts on the Environment for Dietary Studies (DataFRIENDS v3). This tool provides GHGE for as-consumed NHANES foods by aggregating emissions (CO2-equivalents, CO2-eq) from the production of commodity ingredients. GHGE of reported intakes were averaged across the two days for each person and scaled to a 2000-kcal diet. Age was used to approximate birth year and group individuals into either the Silent Generation (≤ 1945), Baby "Boomers" (1946-1964), Gen X (1965-1980), Millennials (1981-1996), or Gen Z (≥< 1997; "Zoomers"). Multivariable linear regression was used to determine differences in dietary GHGE by generation adjusting for sex, race-ethnicity, education, and income. Similar models were run with beef intake as the dependent variable (2-day mean g/2000 kcal). Models including 2005-2008 NHANES data (N=17,570) examined whether GHGE or beef intake changed over the previous decade. Results: Boomers had higher dietary GHGE than Millennials (-6.7% CO2-eq/2000kcal; p < 0.01), Zoomers (-6.8%; p < 0.05), and the Silent Generation (-6.3%; p < 0.05) in fully adjusted models. Boomers also had higher beef intake than these three generations. Gen Xers were not significantly different than Boomers in dietary GHGE or beef intake. There were no significant changes in dietary GHGE over 10 years. Silents reduced average consumption of beef (-13.0%; p< 0.05) over this period, as did Millennials in unadjusted models. Conclusions: Silents, Millennials, and Zoomers had lower dietary GHGE and lower beef intake than Boomers, though dietary GHGE did not change over the previous decade in any cohort. These results can aid in targeting efforts to lower the overall carbon footprint of the US diet. Funding Sources: Wellcome Trust.