Food Group Intakes of Self‐Selected U.S. Diets with High and Low Carbon Footprints

The 2015 Dietary Guidelines Advisory Committee (DGAC) claimed that shifts toward more plant‐based foods would promote health as well as long‐term environmental sustainability of the nation's food supply. Evidence used to reach these conclusions came primarily from studies outside the U.S., since little is known about how individual food choices in this country are related to environmental impacts. To address this gap, we examined dietary patterns of U.S. individuals and their relationships to food‐related greenhouse gas emissions (GHGE). The sample consisted of individuals (N=13,204) aged 18 to 65 from the 2005–2010 National Health and Nutrition Examination Survey (NHANES). We calculated GHGE from the NHANES Day 1 dietary recalls using a food impacts database based on life cycle assessment literature. The database links individual intakes to commodities and environmental impacts. Individuals were ranked by the GHGE per 1000 kilocalories associated with their diet and divided into quintiles. Dietary patterns based on food groups using the USDA Food Pattern Equivalents Database were compared between the lowest and highest quintiles using t‐tests and sample weights and survey design parameters included with NHANES. Compared to those with high dietary GHGE, those in the lowest GHGE group consumed more plant protein foods (0.9 compared to 0.4 oz eq/1000 kcal, p<0.001), and less animal protein foods (1.5 compared to 3.8 oz eq/1000 kcal, p<0.001). Within the animal protein foods, they also consumed more poultry and less red meat. Those with low dietary GHGE consumed significantly more whole grain, more oils, and fewer solid fats. However, they also consumed more refined grains and more added sugars. These results support the DGAC assertion that a diet more sustainable than the U.S. average can be achieved without eliminating any food groups, as even the group with lowest carbon footprint consumed moderate amounts of animal‐based foods. And since these patterns were observed in self‐selected diets, it indicates that such choices are acceptable to some U.S. consumers. While some elements of self‐selected diets lower in GHGE are healthier (e.g. more whole grains and fewer solid fats), other factors are not (e.g. more refined grains and added sugars). This study highlights the complexity in understanding the links between nutritional and environmental objectives and suggests that more attention is needed to address this nascent field of research. Support or Funding Information This work was supported by the Wellcome Trust (grant # 106854/Z/15/Z).