Health Warnings and Beverage Purchase Behavior: Mediators of Impact

Background To reduce diet-related chronic disease, policymakers have proposed requiring health warnings on sugar-sweetened beverages (SSBs). Health warnings reduced purchases of these products by 22% in our recent randomized controlled trial, but the mechanisms remain unclear. Purpose We sought to identify the psychological mechanisms that explain why SSB health warnings affect purchase behavior. Methods In 2018, we recruited 400 adult SSB consumers to complete a shopping task in a naturalistic convenience store laboratory in North Carolina, USA. We randomly assigned participants to either a health warning arm (all SSBs in the store displayed a text health warning) or to a control arm (SSBs displayed a control label). Participants selected items to purchase with cash. Results Compared to control labels, health warnings elicited more attention, negative affect, anticipated social interactions, and thinking about harms (range of ds = 0.63–1.34; all p < .001). Health warnings also led to higher injunctive norms about limiting SSB consumption (d = 0.27, p = .008). Except for attention, all of these constructs mediated the effect of health warnings on SSB purchases (all p < .05). In contrast, health warnings did not influence other attitudes or beliefs about SSBs or SSB consumption (e.g., healthfulness, outcome expectations, and response efficacy). Conclusions Health warnings on sugar-sweetened beverages affected purchase behavior by eliciting negative emotions, increasing anticipated social interactions, keeping SSBs’ harms at top of mind, and shifting norms about beverage consumption. Results are consistent with recent studies of why tobacco warnings influence quitting behavior, pointing toward a general framework for understanding how health warnings affect behavior. Clinical Trials Registration NCT #03511937.