Environmental Impact of Current Diets and Alternative Dietary Scenarios Worldwide: A Systematic Review.

Context: Unhealthy and unsustainable diets are common worldwide. Health and sustainability need to be balanced because environmentally sustainable diets may lack macro- and/or micronutrients, resulting in nutrient deficiencies.

Objective: A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines to analyze the environmental impact of current diets and alternative dietary scenarios worldwide based on food-group consumption.

Data sources: The Scopus, Web of Sciences, and PubMed literature databases were searched. Only studies quantifying the food composition of diets per food group and their environmental impact were eligible.

Data extraction: Data were extracted for food groups as averages, means, or medians, depending on how they were reported in the original publication, for both environmental impact indicators and grams consumed.

Data analysis: A total of 120 original articles from 41 countries were included and 703 diets were analyzed. Current diets were the most prevalent (42%). Among the environmental indicators, carbon footprint (CF) was the most reported (86% of diets), followed by land (36%), total freshwater (22%), blue water (15%), and cumulative energy use (14%). Data about food consumption and environmental impact were available mainly for European countries (n = 471 diets; 67%), and Africa was the most underrepresented continent, with data from only 2 countries.

Conclusion: The environmental impact of food consumption varied widely among diet types and continents, due to methodology heterogeneity of dietary assessment and different definitions of diets and food groups. Diets enhancing healthiness, such as the Mediterranean diet and food-based dietary guidelines, were associated with a higher CF than diets reducing meat consumption. Furthermore, diets including meat substitutes were associated with a higher CF than other plant-based diets that did not include them. Affordable diets involved more freshwater use, whereas acceptable diets that include high amounts of meat intake had a high CF. Finally, extensive research on dietary intake and environmental impact in low- and middle-income countries is required due to lack of available studies and data in these areas.