Do alcohol product labels stating lower strength verbal description, percentage alcohol-by-volume, or their combination affect wine consumption? A bar laboratory adaptive randomised controlled trial

Abstract

Background and Aims: A previous research study concluded that wine and beer labelled as lower in strength increase consumption compared with the same drinks labelled as regular strength. The label included both a verbal and numerical descriptor of strength. The present study aimed to estimate the effect of each of these label components. Design: Adaptive, parallel group randomised controlled trial, comprising an internal pilot sample (n1 = 90) and a confirmatory sample (n2 = 57). Setting: University bar laboratory in London, United Kingdom (UK). Participants: A total of 147 weekly wine drinkers were sampled from a nationally representative English panel. Intervention: Participants were randomised to one of three groups to taste test wine in a bar-laboratory, varying only in the label displayed: (i) verbal descriptor only (Super Low); (ii) numerical descriptor only (4% alcohol by volume (ABV)); and (iii) verbal descriptor and numerical descriptor combined (Super Low 4%ABV) (each group n = 49). Measurements: The primary outcome was total volume (ml) of wine consumed. Findings: Participants randomised to the numerical descriptor label group (4%ABV: M = 155.12 ml, B = 20.30; 95% CI = 3.92, 36.69; P value = 0.016) and combined verbal and numerical descriptor label group (Super Low 4%ABV: M = 154.59 ml, B = 20.68; 95% CI = 4.32, 37.04; P value = 0.014) drank significantly greater amounts than those randomised to the verbal descriptor label group (Super Low: M = 125.65 ml). Conclusions: This bar laboratory study estimated that a greater quantity of ‘lower’ strength wine was consumed when the label included a numerical strength descriptor compared with a verbal only strength descriptor.