The effects of nudging and pricing strategies on the availability and purchases of ultra-processed foods: A secondary analysis of the Supreme Nudge trial

Regular consumption of ultra-processed foods (UPF) is a risk factor for morbidity and mortality. UPF are widely available in supermarkets. Nudging and pricing strategies are promising strategies to promote healthier supermarket purchases and may reduce UPF purchases. We investigated whether supermarket nudging and pricing strategies targeting healthy foods, but not specifically discouraging UPF, would change UPF availability, price, promotion and placement (UPF-APPP) in supermarkets and customer UPF purchases. We used data from the Supreme Nudge parallel cluster-randomized controlled trial, testing the effect of a combined nudging and pricing intervention promoting healthy products. The Dutch Consumer Food Environment Score (D-CFES) was used to audit 12 participating supermarkets in terms of UPF-APPP. We used customer loyalty card data of the first twelve intervention weeks from 321 participants to calculate the proportion of UPF purchases. Descriptive statistics were used to assess differences in D-CFES between supermarkets. Mixed model analyses were used to assess the association between the D-CFES and UPF purchases and the effect of the intervention on UPF purchases. No difference in the D-CFES between intervention and control supermarkets were found. No statistically significant association between the D-CFES and UPF purchases (β = −0.00, 95%CI: −0.02, 0.01) and no significant effect of the intervention on UPF purchases (β = 0.02, 95%CI: −0.07, 0.12) was observed. Given the significant proportion of unhealthy and UPF products in Dutch supermarkets, nudging and pricing strategies aimed at promoting healthy food purchases are not sufficient for reducing UPF–APPP nor purchases, and nationwide regulation may be needed.Trial registration number: Dutch Trial Register ID NL7064, May 30, 2018, https://trialsearch.who.int/Trial2.aspx?TrialID=NTR7302.