Affiliation: Gillings School of Global Public Health, Department of Nutrition
Objectives: Food systems are a key driver of climate change and poor health. A major food system shift over the last few decades is increased ultra-processed food (UPF) consumption. High UPF consumption is extensively linked with poor diet quality and chronic diseases, but the environmental impacts of UPFs are less explored. We used a nationally representative survey to evaluate the association between UPF consumption and greenhouse gas emissions (GHGEs) among US adults.
Methods: This is a cross-sectional study with two pooled waves of data (2007-2008 and 2009-2010) from the National Health and Nutrition Examination Survey (NHANES). Foods were classified according to NOVA based on degree of processing. We divided participants into quintiles based on proportion of diet from UPFs using mean of two-day dietary recall. Foods reported in NHANES were matched with GHGEs using the database of Food Recall Impacts on the Environment for Nutrition and Dietary Studies (dataFRIENDS). Dietary GHGEs were measured in kilograms of carbon dioxide equivalents per person per day per 1000 grams of food (kg CO2-eq). Multivariate linear regression models were used to test the association between quintiles of UPF consumption and dietary GHGEs. We estimated the survey-weighted distribution of sociodemographic characteristics (age, sex, income, education, and race/ethnicity) by quintile of UPF consumption and GHGE.
Results: Consuming a greater proportion of diet from UPFs was associated with greater dietary GHGEs (ptrend<0.001). The estimated relative GHGEs for the lowest quintile of UPF consumption were 1.19 (95% CI: 1.12, 1.27) kg CO2-eq, compared to 1.71 (95% CI: 1.65, 1.77) kg CO2-eq for the highest UPF quintile, showing a 43% increase. Adults who were younger, had lower incomes, had less education, and who were non-Hispanic Black were more likely to be in the highest quintile of UPF intake. Adults who were male, had lower incomes, had less education, and who were non-Hispanic Black were more likely to be in the highest quintile of relative GHGEs.
Conclusions: Diets with a greater proportion of UPFs tend to be higher in GHGEs. These results suggest that policies to reduce UPFs could have health and environmental co-benefits, though more research is needed to understand the mechanisms behind why UPFs are associated with GHGEs.