However, much of that work had been conducted using measurements of sustainability for broad categories of food instead of specific food items, leaving room for greater accuracy in evaluating the environmental impact of individual diets.
Working towards better accuracy, Rippin and colleagues evaluated existing published research in order to assign greenhouse gas emissions to over 3,233 specific food items listed in the UK Composition Of Foods Integrated Dataset (COFID).
Men's diets were linked to emissions that were 41 per cent higher than emissions associated with women's diets, primarily due to greater meat intake
COFID already contained nutrition data and is commonly used to evaluate the nutrition of individuals' diets. Then, 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 non-vegetarian diets were associated with greenhouse gas emissions that were 59 per cent higher than emissions associated with vegetarian diets.
Men's diets were linked to emissions that were 41 per cent higher than emissions associated with women's diets, primarily due to greater meat intake. And people whose intake of saturated fats, carbohydrates, and sodium met levels recommended by the World Health Organisation had lower greenhouse gas emissions than people who exceeded recommended levels of those nutrients.
These findings supported a focus on plant-based foods for policies meant to encourage sustainable diets. It also suggested 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 to 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."