Carbon footprint of Canadian self-selected diets: Comparing intake of foods, nutrients, and diet quality between low- and high-greenhouse gas emission diets

Individuals' dietary choices are critical determinants of human and planetary health. Although the carbon footprint of animal-based foods typically exceeds that of plants, trade-offs among nutritional outcomes and environmental sustainability in the context of regional self-selected diets are less understood. The objectives were to estimate the carbon footprint of Canadian self-selected diets and to compare intake of food groups, nutrients, and diet quality between low-and high-greenhouse gas emission (GHGE) diets. Dietary intake was assessed using 24-h recalls from the 2015 Canadian Community Health Survey (CCHS) - Nutrition for adults >= 19 y (n = 13,612). Estimates from the database of Food Impacts on the Environment for Linking to Diets were used to link foods and beverages reported in the CCHS to their GHGE. Boundaries for GHGE estimates were mostly cradle-to farm gate and for certain processed products, cradle-to-processing gate. Data from Statistics Canada were used to account for food loss at the retail and consumer levels in our calculation of GHGE. The Alternative Healthy Eating Index-2010 was used to calculate diet quality. The study sample was divided into quintiles based on their diet related GHGE expressed per 1,000 kcal; low-and high-GHGE diets were those of respondents in the lowest and highest quintiles, respectively. Dietary GHGE (mean +/- SE) was 3.98 +/- 0.06 kg carbon dioxide-equivalents (CO2-eq) per person per d or 2.15 +/- 0.03 kg CO2-eq per 1,000 kcal. Animal-based foods contributed three-quarters of Canadians' total diet-related GHGE, with red and processed meat alone accounting for 47.05 +/- 0.82%. High-GHGE diets contained more animal-based foods, vegetables and fruit, and miscellaneous foods and beverages, whereas low-GHGE diets contained more cereals, grains, and breads. Moreover, high-GHGE diet respondents had higher intakes of nutrients of public health concern (calcium, vitamin D, iron, and potassium), but also higher intakes of saturated fat and sodium, and a lower overall diet quality compared to low-GHGE diet respondents (47.27 +/- 0.46 vs. 55.31 +/- 0.49 points). These nutritional and environmental trade-offs warrant attention in shaping future food policy and dietary guidance in Canada aimed at meeting global targets for climate change.