Healthier diets linked to lower CO2 emissions

The analysis assigned emissions to individual food items rather than broad food groups for greater accuracy. Analyses of this sort tend to evaluate sustainability at the scale of broad food-group categories.

Food production is a major source of greenhouse gas emissions, accounting for approximately one third of emissions. The more sustainable diets are generally considered to be – based on previous research – those based around nutritious, unprocessed, less energy-dense food. However, much of that work has been conducted using measurements of sustainability for broad categories of food.

This leaves room to improve methodology. This study, which assigns emissions to individual food items instead of broad food groups, provides greater accuracy than before.

Dr Holly Rippin, of the University of Leeds, evaluated existing published research in order to assign greenhouse gas emissions to over 3,233 food items listed in the UK Composition of Foods Integrated Dataset (COFID). COFID already contains nutrition data and is commonly used to evaluate the nutrition of individuals’ diets. Next, the researchers used the combined emissions and nutrition information to evaluate the diets of 212 adults who reported all the foods they ate within three 24-hour periods.

Statistical analysis of the reported diets showed that the non-vegetarian diets were associated with greenhouse gas emissions that were 59 per cent higher than emissions associated with vegetarian diets. Men’s diets, meanwhile, were linked to emissions on average 41 per cent higher than women’s diets, primarily due to higher meat intake. Those with WHO-approved intake of saturated fats, carbohydrates, and sodium had lower diet-related emissions than those who exceeded recommended levels.

These findings support a focus on plant-based foods for policies meant to encourage sustainable diets. Perhaps more controversially, it also suggests both environmental and nutritional benefits for replacing coffee, tea, and alcohol with more environmentally sustainable substitutes.

In the future, similar research efforts could provide further clarity by incorporating such details as food item brand, country of origin, and other indicators of environmental impact, beyond emissions.

The authors added: “We all want to do our bit to help save the planet. Working out how to modify our diets is one way we can do that.”

“There are broad-brush concepts like reducing our meat intake, particularly red meat, but our work also shows that big gains can be made from small changes, like cutting out sweets, or potentially just by switching brands.”