Loyalty Card Data for Assessing Dietary Interventions: A Narrative Review

Objective: This review examines the use of loyalty card data for assessing dietary interventions. Design: By analysing challenges and opportunities across eleven studies—identified through a previous scoping review—we use a narrative approach to discuss the validity and reliability of loyalty card data as a tool for assessing the effectiveness of dietary and health interventions.Setting: The studies included in this review were identified through a prior scoping review exploring the use of supermarket loyalty card data to examine health outcomes. A comprehensive search of databases—including MEDLINE, EMBASE, PsycINFO, and Scopus—was carried out using keywords related to shopping, loyalty cards, and health. A subset of studies evaluating dietary interventions was selected for the present review.Participants: n/a.Results: Loyalty card data can provide valuable insights into consumer dietary choices, offering a scalable tool for evaluating dietary interventions within a retail setting. The effectiveness of existing interventions were mixed. There were challenges such as confounding, small sample sizes, and retailer involvement that affected results. Regardless, loyalty card data holds significant potential for large-scale interventions, especially when combined with complementary data sources. There are opportunities for interventions to influence policy, reducing dietary and nutritional inequalities to improve outcomes for vulnerable groups. Finally, online platforms may help to improve the accuracy of interventions by triangulating data sources, and personalised feedback should be explored to maximise effectiveness.Conclusion: Despite limitations, loyalty card data presents a promising opportunity for evaluating dietary interventions, particularly when used alongside other data sources and supported by policymakers and retailers.