Digital nudging toward sustainable healthy foods: Insights from a trial on a university-based dashboard for promoting sustainable eating habits.

Sustainable diets are promoted to reduce environmental impacts while supporting public health, yet translating sustainability information into healthier food choices remains challenging. This study evaluated whether the Dashboard for Improving Sustainable Healthy (DISH) Food Choices, a digital food environment providing real-time environmental and nutritional information, could encourage more sustainable and nutritionally balanced meal selections. DISH was deployed as a mobile app, website, and kiosk in two university campus cafeterias over 10 weeks. The primary behavioural outcomes were the nutritional quality and environmental impact of selected meals, operationalized through pre- and post-intervention meal scores: Food Compass Score and Health Star Rating for nutritional quality, and climate change score for environmental impact. Data were collected from 189 participants randomly assigned to control and intervention groups (n = 85 and n = 86, respectively), with surveys complemented by exploratory interviews with 26 intervention participants four months later. These interviews were guided by the Capability, Opportunity, Motivation-Behaviour (COM-B) model. Both an intention-to-treat repeated-measures model and complementary non-parametric tests (Wilcoxon and Mann-Whitney U) indicated that exposure to DISH's combined environmental-nutritional information did not significantly influence food choices on any behavioural measure (p > 0.47). Latent profile analysis identified a subgroup with high health motivation but low climate consideration; however, since this subgroup appeared in both study groups and was not differentially affected by the intervention, it should be viewed as a target for future tailored strategies rather than evidence of intervention effectiveness. Qualitative feedback suggested that DISH increased awareness and reinforced sustainability concepts. Overall, the findings highlight both the promise and limitations of digital tools for supporting informed dietary decisions and underscore the need to strengthen motivational and contextual relevance to achieve behavioural impact.