Shopping Data for Epidemiological Research: Opportunities, Challenges, and Future Directions

This position paper explores the value of supermarket loyalty card data as a novel resource for epidemiological research. Routinely collected at the point of purchase, these data offer high-resolution, longitudinal insights into real-world behaviours. We examine key applications across four core domains—diet, alcohol, tobacco, and over-the-counter medications—and consider how loyalty card data can supplement traditional epidemiological approaches by improving exposure measurement and supporting the evaluation of public health interventions. The paper also addresses key methodological and ethical challenges, including representativeness, data linkage, and privacy. We conclude by outlining future directions for embedding loyalty card data more widely in epidemiological research through linkages with existing health records and longitudinal population studies.