Environmental Impacts of Diets: Development of an LCA Database to Link to Individual's Food Choices in the United States
The recent recommendation to include sustainability considerations in the Dietary Guidelines for Americans has raised interest in the environmental impact of diets in a U.S. context. A few aggregate U.S. diet studies exist, but our work addresses the environmental impacts of individual diet choices, which is needed to accurately estimate the impacts of behavioral changes and thereby improve policy. Here we describe the development of a food environmental impact database linkable to individual food choices in the U.S. which could be used to estimate the variation individual diet-induced cumulative energy demand and greenhouse gas emissions. Individual dietary recall data from the National Health and Nutrition Examination Survey for 2005-2010 serves as the basis for individual food choices; the more than 7,000 foods consumed are linkable to 354 commodity foods. To assign environmental impacts to these food commodities, we conducted a comprehensive review of LCA studies published since 2005. Impact factors along with metadata on scope and production characteristics ere included in the database. The food LCA review identified 193 unique publications and 305 "metrics", or unique combinations of food type and life cycle production scenario. Twenty-eight percent of LCA entries went through the retail stage; 97% of entries considered global warming potential while only 37% included cumulative energy demand. Even with this extensive literature review, 37% of the food commodity items required proxies to link to global warming potential impacts. Data gaps were particularly noteworthy in herbs and spices, lightly processed food forms of fruits and vegetables (juices, dried), and some major cooking oils. Despite the frequent use of proxies, they accounted for only 2% of diet-level global warming potential, as the foods assigned proxy tended to be low impact and less frequently consumed foods. This cross-disciplinary research demonstrates an approach that can inform policy discussions regarding the sustainability of dietary choices, but it also points to research gaps that must be filled by the LCA community in order to improve on the available information.