Impact of a default nudge intervention on plant-based milk consumption in a UK university café

Abstract

Encouraging plant-based food consumption among western consumers is vital for reducing the environmental impacts of animal agriculture. This study examined the impact of a default nudge intervention on sustainable plant-based milk consumption in a UK university café using an ABAB experimental design. During the intervention phases, the menu’s default milk option was changed from dairy milk to oat milk. In the first intervention phase we found that café customers were approximately three times more likely to consume plant-based milk when oat milk was the default milk option instead of dairy milk (from 16.6% to 51.9%). However, the intervention effect was smaller in the second intervention phase compared to the first (from 51.9% to 46.0%), potentially questioning the long-term impact of default nudges on sustainable food consumption. Comparable data in a second café at the same university found no differences in plant-based milk intake during the study period, suggesting that the observed changes in plant-based milk consumption were due to the default nudge. Based on these intervention effects, the average milk-based carbon footprint per drink was estimated to have reduced by 25-34%. These findings suggest that default nudges can encourage plant-based food consumption by reducing dairy intake and increasing plant-based milk consumption. This provides implications for the adoption of sustainable default nudges in both the university and wider food sector to help increase plant-based diets among consumers and reduce the environmental damage caused by animal agriculture.