Self-Selected Diets in the US Show a Reduction in Carbon Footprints Over Ten Years

Abstract

ObjectivesGrowing evidence indicates the need for demand-side changes to global food systems to meet nutritional needs while staying within planetary boundaries. Previous research documented the greenhouse gas emissions (GHGE, or carbon footprint) of self-selected diets in the US from the 2005–2010 National Health and Nutrition Examination Survey (NHANES), but more recent such data do not exist. To address this gap, we assessed the carbon footprint of diets reported in the 2015–2016 NHANES, and analyzed the 10-year trend from the 2005–2006 wave. MethodsFoods eaten by adults (N = 5,060), ages 18 years and older, reported in a one-day 24-hour recall in NHANES 2005–2006 were translated to commodity intakes using recipes from the US Environmental Protection Agency’s Food Commodity Intake Database (FCID). GHGE (kg carbon dioxide equivalents, or CO2-eq, per kg of edible portion) in the production of these commodities were calculated from the database of Food Impacts on the Environment for Linking to Diets (dataFIELD), then summed for each person to get a total one-day dietary carbon footprint. Newly reported foods consumed by adults (N = 4,982) in 2015–2016 required new recipes to be translated to commodity intakes. We developed these recipes by modifying similar existing FCID recipes. If no similar food existed, recipes were constructed using ingredients and proportions from the US Department of Agriculture’s FoodData Central. ResultsMean food-related GHGE decreased 7.9% across the ten-year period, from 4.9 to 4.5 kg CO2-eq/day. Controlling for energy intake, age, gender, race, and income-to-poverty ratio, one-day food-related GHGE were still lower in 2015–2016 than they were in 2005–2006, by 0.3 kg CO2-eq (p < 0.02). ConclusionsThe average carbon footprint of US adults’ self-selected diets has decreased over time. This is a positive development for efforts to slow climate change. However, evidence reported elsewhere shows that US diets do not meet current nutritional recommendations. Additional research is needed to find and encourage “win-win” diets that meet nutritional objectives, while reducing environmental impacts. Funding SourcesWellcome Trust, National Cancer Institute, Health Resources and Services Administration.