Changing dietary patterns is necessary to improve the sustainability of Western diets from a One Health perspective.

Western diets are associated with multiple environmental impacts and risks to human health. European countries are gradually taking action towards the Farm to Fork Strategy, embracing a Life Cycle Assessment (LCA) perspective to promote the sustainability of food production and consumption. Although LCA enables the comprehensive assessment of environmental impacts, diet-related human health and animal welfare impacts are often underrepresented. This study proposes integrating additional indicators into LCA to evaluate the sustainability of diets under the One Health (OH) approach, which holistically considers interlinked complex health issues between humans, animals and the environment. Human health loss is estimated according to risk factors for non-communicable diseases; while animal welfare is measured as animal life years suffered, loss of animal lives and loss of morally-adjusted animal lives. The extended LCA framework is applied to men and women's reference diets in the German federal state of North Rhine-Westphalia (NRW); compared to three optimized dietary scenarios under nutritional constraints: 1) the national dietary guidelines, 2) a vegan diet (VD) and 3) a Mediterranean diet (MD). Men's reference diet causes greater impacts than women's across OH dimensions due to the higher food consumption, especially of ready-to-eat meals, sausages, meat, and sweetened and alcoholic beverages. Both reference diets are associated with risk factors for cardiovascular diseases, diabetes, stroke and neoplasms. Besides meat, consumption of honey, fish and seafood has the greatest impact on animal welfare, because of the high number of individuals involved. Alternative diets improve the sustainability of food consumption in NRW, although trade-offs arise: MD worsens animal suffering due to the higher fish intake; water use increases in both VD and MD due the higher intake of nuts and vegetables. Results highlight the importance of including animal welfare and human health indicators in LCA to better elucidate the potential impacts of diets characterized by the high intake of animal products, from a OH perspective.