Effects of front-of-package nutrition labelling systems on objective understanding and purchase intention in El Salvador : results from a multi-arm parallel-group randomised controlled trial

Abstract

Purpose Front-of-package labelling (FOPL) schemes have been developed to provide more useful information to consumers and facilitate more critical and healthier food choices. This single-blinded multi-arm parallel-group randomised controlled trial aimed at assessing the effect of different FOPL schemes on the objective understanding of the nutritional content and intention to purchase products, in El Salvador. Methods Participants (n = 1204) were exposed to two-dimensional images of 15 mock-up products presented at random and balanced orders. Participants were exposed to mock-ups featuring no FOPL scheme (control group, n = 305) or one of the following schemes: black octagonal warning labels (OWL) (n = 302), traffic-light labelling (TFL) (n = 297), or guideline daily amounts (GDA) (n = 300). Results The odds for choosing to purchase the least harmful of the options more often was the highest in the OWL group compared to the control group: two times higher in the OWL group (OR 2·21, 95% confidence interval 1·58 − 3·11), and 49% higher in the TFL (1·49, 95%CI 1·06 − 2·11), with no changes in the GDA (1·06, 95%CI 0·75 − 1·50). OWL also resulted in the highest odds for correctly identifying the least harmful option (OR 3·77, 95%CI 2·79 to 5·09), and for correctly identifying a product with higher amounts of sugars, sodium, total fat, and/or saturated fats (3·26, 95%CI 2·40 to 4·43). Conclusion OWL outperformed GDA and TFL in its ability to improve objective understanding of nutritional information and purchase intention. Results support the adoption of OWL in El Salvador.