Reducing the Carbon Footprint of Diets Across Socio-Demographic Groups in Finland: A Mathematical Optimization Study.

OBJECTIVES:To characterize nutritionally adequate, climate-friendly diets that are culturally acceptable across socio-demographic groups. To identify potential equity issues linked to more climate-friendly and nutritionally adequate dietary changes. DESIGN:An optimization model minimizes distance from observed diets subject to nutritional, greenhouse gas emissions (GHGE) and food-habit constraints. It is calibrated to socio-demographic groups differentiated by sex, education and income levels using dietary intake data. The environmental coefficients are derived from life cycle analysis and an environmentally-extended input-output model. SETTING:Finland. PARTICIPANTS:Adult population. RESULTS:Across all population groups, we find large synergies between improvements in nutritional adequacy and reductions in GHGE, set at one third or half of current level. Those reductions result mainly from the substitution of meat with cereals, potatoes and roots, and the intra-category substitution of foods, such as beef with poultry in the meat category. The simulated more climate-friendly diets are thus flexitarian. Moving towards reduced-impact diets would not create major inadequacies related to protein and fatty acid intakes but iron could be an issue for pre-menopausal females. The initial socio-economic gradient in the GHGE of diets is small, and the patterns of adjustments to more climate-friendly diets are similar across socio-demographic groups. CONCLUSIONS:A one-third reduction in GHGE of diets is achievable through moderate behavioural adjustments, but achieving larger reductions may be difficult. The required changes are similar across socio-demographic groups and do not raise equity issues. A population-wide policy to promote behavioural change for diet sustainability would be appropriate.