A traffic light system rating the eco-friendliness of foods on a menu leads to more people choosing vegetarian dishes, a study suggests. Research by the University of Bristol involved 1,399 adults being shown mocked up food delivery app menus featuring three burritos - one beef, one chicken and one vegetarian - with different accompanying information.
All menus contained a photograph of each item, as well as the calorie count, a Fairtrade logo, a spice indicator and the price, which was the same for all three. One mock-up featured the 'social nudge' of a gold star and the words 'most popular' placed alongside the vegetarian burrito.
Another menu had a traffic light system rating the eco-friendliness of each burrito - with beef scoring a red five, chicken scoring a yellow three, and the vegetarian option marked as a green one. Participants in the study were shown one of the three menu mock-ups and asked to pick a burrito option as if they were normally ordering food.
Five per cent more participants chose the vegetarian option when the eco-labels were included, while 17% more went for vegetarian or chicken.
Lead author Katie De-loyde, research associate in psychological science at the University of Bristol, said participants were also asked follow-up questions. She said: "Adding a traffic light eco-label to menus increased the selection of more sustainable food items.
"Furthermore, and somewhat surprisingly, participants were positive about the eco-label, with a huge 90% of participants supporting the idea. Pending replication in real-world settings, our results suggest future policy could include mandatory eco-labelling, just like the health traffic light system, on food products as a way to promote more sustainable diets."
She said the label was particularly effective among people who reported already being motivated to act sustainably. The study, published in the journal Behavioural Public Policy, found one third of the participants given the control menu - without a social nudge or eco-label - chose the beef burrito.
This dropped to 29% for those with the social nudge menu and to 16% for those with the eco-labelled menu. Only 9% of participants with the control menu chose the vegetarian burrito. However, this increased to 13% with the social nudge and 14% with the eco label.
The University of Bristol, the first UK university to declare a climate emergency, has introduced eco-labels on menus in catered halls for students this academic year. Students are also helping with a trial by the university's School of Psychological Science to monitor which sandwiches, each featuring details of its carbon footprint, sell best.
Co-author Dr Olivia Maynard, from the University of Bristol, said: "In 2020, the UK's Committee on Climate Change advocated that beef consumption must be considerably reduced if the UK is to reach its net-zero greenhouse-gas emission target by 2050. Although further research on eco-labelling is essential, future policy may wish to consider a mandatory eco-label to help meet global climate change targets."
